On the ground floor of the National Institutes of Health Chemical Genomics Center (NCGC) in Rockville, Maryland, a $10-million automated laboratory spends all day and night screening chemicals at speeds no team of human researchers could ever match. In a week, depending on the nature of the assay, it can yield up to 2.2 million molecular data points derived from thousands of chemicals tested at 15 concentrations each.
Is this the new face of toxicology? Many experts say the answer could be yes. High-throughput screening tools such as the NCGC’s robotic system—combined with a growing assortment of in vitro assays and computational methods—are revealing how chemicals interact with biologic targets. Scientists increasingly believe these tools could generate more accurate assessments of human toxicity risk than those predicted by animal tests now. What’s more, in vitro analytical approaches are seen as the best hope for evaluating the enormous backlog of untested chemicals in commerce. Estimates vary, but tens of thousands of industrial chemicals are used in consumer products without any knowledge of their potential toxicity. Meanwhile, it takes years and millions of dollars to assess risks for a single chemical using animal testing.
“In almost all aspects, this looks like a paradigm shift in the field,” says John Bucher, associate director of the National Toxicology Program (NTP). “It’s a major change to move from using studies in animals, with which we’re comfortable, to relying mainly on results from biochemical or cell-based assays to make health policy decisions. This is a totally different approach that provides a different kind of information.”
The Tox21 Partnership
Enabled by new technology, the NTP, the NCGC, and the U.S. Environmental Protection Agency (EPA) are partnering to advance the state of toxicity testing. Specifically, the partners seek to identify new mechanisms of chemical activity in cells, to prioritize the backlog of untested chemicals for more extensive evaluations, and to develop better predictive models of human response to toxicants. Formalized last year in a Memorandum of Understanding, the partnership, dubbed Tox21, responds to a challenge made by the National Research Council (NRC) in its 2007 report Toxicity Testing in the 21st Century: A Vision and a Strategy. This report called for transforming toxicology “from a system based on whole-animal testing to one founded primarily on in vitro methods that evaluate changes in biologic processes using cells, cell lines, or cellular components, preferably of human origin.” In March 2009, the EPA published its own Tox21 agenda, The U.S. Environmental Protection Agency’s Strategic Plan for Evaluating the Toxicity of Chemicals, which asserts that “the explosion of new scientific tools in computational, informational, and molecular sciences offers great promise to . . . strengthen toxicity testing and risk assessment approaches.”
The concept of adding more mechanistic data to risk assessment isn’t new. Before Tox21, physiologically based pharmacokinetic (PBPK) models, toxicogenomics, and related approaches were already making risk assessment more mechanistically based. But that research didn’t necessarily translate into changes in regulatory policies that govern human exposure, argues Lorenz Rhomberg, a principal with Gradient Corporation, a risk assessment consulting firm in Cambridge, Massachusetts. Despite the availability of mechanistic data, health officials at the EPA have been reluctant to use these data in setting exposure standards because in many cases they would justify higher allowable exposures than those suggested by more conservative default assumptions. Instead, the EPA relies more often on conservative default assumptions about how chemicals affect human beings. “EPA goes by precedent and does things as it did in the past so as to not be arbitrary,” Rhomberg explains. “So, there’s a lot of inertia in the system.
Monday, August 3, 2009
Chemicals can turn genes on and off; new tests needed, scientists say.
Each of us starts life with a particular set of genes, 20,000 to 25,000 of them. Now scientists are amassing a growing body of evidence that pollutants and chemicals might be altering those genes—not by mutating them, but by sending subtle signals that silence them or switch them on at the wrong times.
Last week, several dozen researchers and experts convened by the National Academies tackled this complicated topic, called epigenetics, at a two-day workshop in Washington, D.C. They discussed new findings that suggest chemicals in our environment and in our food can alter genes, leaving people vulnerable to a variety of diseases and disorders, including diabetes, asthma, cancer and obesity. They also considered whether regulatory agencies and industry should start testing the thousands of chemicals in use today for these effects.
“There is little doubt these epigenetic effects are important. The next question is how we test for effects," said William H. Farland, professor of environmental and radiological health sciences at Colorado State University. "We don’t need to abandon current approaches to chemical testing. When testing chemicals in animals, we may just need to add some new endpoints."
Linda S. Birnbaum, Director of the National Institute of Environmental Health Sciences
Exposure to gene-altering substances, particularly in the womb and shortly after birth, “can lead to increased susceptibility to disease,” said Linda S. Birnbaum, who was named director of the National Institute of Environmental Health Sciences and of the National Toxicology Program in December. “The susceptibility persists long after the exposure is gone, even decades later. Glands, organs, and systems can be permanently altered.”
Animal studies indicate that some environmental chemicals cause epigenetic changes that trigger breast and prostate cancer, obesity, diabetes, heart disease, asthma, Alzheimer’s, Parkinson’s disease and learning disabilities, she said. And some new human studies are now adding to the evidence.
“There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and grandmother were exposed to during pregnancy,” Birnbaum said. “There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and grandmother were exposed to during pregnancy.” Linda Birnbaum, Director, National Institute of Environmental Health Sciences
What a pregnant mother eats and the chemicals she is exposed to can affect her offspring without causing mutations in the DNA, the experts said. Instead, such exposures can disrupt the way that genes behave, according to both animal and human studies. These changes, in turn, can be passed on to the next generations.
Some environmental chemicals enable methyl groups (carbon atoms with three hydrogen atoms attached) to attack genes, which turns them off or mutes them, at a time when they should be turned on. When genes are turned off, they can’t direct the manufacture of proteins that are essential for proper cell function. Chemicals also can uncoil parts of the chromosome, causing genes to be expressed, or turned on, at inappropriate times.
An example is asthmatic children. Wan-Yee Tang, a researcher at the University of Cincinnati, found that children in New York City exposed in the womb to high levels of polycyclic aromatic hydrocarbons (PAHs), common air pollutants from traffic, were much more likely to have asthma than those who were not exposed. By studying cord blood, she found that a particular gene (ACSL3) was methylated in the asthmatic children and unmethylated in the unexposed children, and concluded that the abnormal methylation patterns probably caused the asthma.
The finding could in part explain why worldwide asthma rates have skyrocketed in much of the world, reaching epidemic proportions among children. In the boroughs of New York City with the worst air pollution, about 25 percent of children are asthmatic.
Epigenetic changes also have been observed in children conceived with assisted reproductive technologies, said Richard Meehan of the Medical Research Council in Scotland.
One of the disorders that occurs at a higher rate in these children is Beckwith-Wiedemann syndrome, which is characterized by abdominal wall defects and a higher risk of certain childhood cancers. The culture medium where fertilized eggs are grown for several days before implantation probably causes the syndrome, he said. It appears that all the different media used for the eggs might be problematic because they contain chemicals that stimulate the addition of methyl groups to the cells.
The scientists at the workshop said it’s important to understand epigenetics not only to figure out which chemicals might endanger public health, but to find new ways to prevent or treat diseases.
Scientists are just now beginning to figure out normal methylation patterns in the genome so they can learn what is abnormal, said Karl T. Kelsey, professor of community heath and pathology at Brown University in Rhode Island. As a result of this new understanding, epigenetic therapies have been developed for some types of cancers, and some have been successful in clinical trials, he said. Unlike traditional cancer drugs, which kill cells, the new drugs simply change how the cells act.
Research with rats shows that gene-altering chemicals can change animals’ brains—in some cases, in a beneficial way.
Moshe Szyf, a pharmacology and therapeutics professor at McGill University Medical School in Montreal, found that rats that received healthy doses of maternal licking as pups grew up to be calmer than pups who had inattentive mothers. The maternal grooming brought about a chemical change in the part of the pup’s brain that produces stress hormones, he said.
The rats reared by attentive mothers had different levels of corticoid gene expression and lower levels of stress hormones than those reared by inattentive mothers. Szyf found he could cure the stressed rats by injecting a chemical called TSA into their brains, which reversed the inappropriate methylation caused by inattentive mothering.
This understanding of epigenetics may lead to new medications for treating human problems. By using approaches similar to those used in the rat study, Szyf is hoping to find drugs that will help alleviate human psychiatric conditions.
Szyf also studied the preserved brains of suicide victims and of people who died suddenly from causes other than suicide. He found that certain genes in the suicide victims were methylated, or turned off. In contrast, those same genes were not methylated in the victims who died by other means. Abnormal methylation patterns could cause depression in some people, he said.
Some compounds, such as nickel, chromium and arsenic, are well-known carcinogens—not because they are toxic to cells but because of their epigenetic effect, said Max Costa, a New York University professor of environmental medicine and pharmacology. They increase DNA methylation, which results in gene silencing and cell transformation and leads to cancer, he explained.
Researchers at the meeting spent a great deal of time discussing whether and how to test chemicals for their ability to cause epigenetic changes.
Most researchers there agreed that compounds need to be tested for epigenetic effects. But practical testing of the 80,000 or so chemicals in commerce would require rapid screens that would prioritize the compounds into high, medium, and low-risk groups. Those at high risk for epigenetic effects could then be subjected to more definitive and expensive tests.
John M. Greally, associate professor at the Albert Einstein College of Medicine in New York City, pointed out that no single test is ideal for detecting epigenetic effects.
“All of the assays have drawbacks,” he said. For example, one assay requires immediate sample processing so it cannot be used on stored samples.
Nevertheless, many researchers said that testing chemicals for epigenetic changes can begin soon.
“The fact that we don’t know a great deal about this area doesn’t mean it’s daunting,” said George Daston, research fellow at Procter & Gamble. “We just need to build on what we have. Microassays already show how chemical exposures change the gene expression in certain parts of the genome. The fact that we don’t know a lot doesn’t mean we can’t start testing quickly.”
Birnbaum, who formerly was head of experimental toxicology at the U.S. Environmental Protection Agency, said regulators and industry don’t have to start from square one.
“We’re already marching down this road,” said Birnbaum. “The National Toxicology Program is already talking about including some epigenetic studies in the program.”
The most important public health issue that arises from epigenetics, Birnbaum told Environmental Health News, is that the current environment may not be the crucial factor to consider when examining what causes diseases.
“Asking heart attack victims what they ate this year or last may be far less important than what they were exposed to in the womb and shortly after birth,” she said.
What a pregnant mother eats and the chemicals she is exposed to can affect her offspring without causing mutations in the DNA, the experts said. Instead, such exposures can disrupt the way that genes behave, according to both animal and human studies. These changes, in turn, can be passed on to the next generations.
Some environmental chemicals enable methyl groups (carbon atoms with three hydrogen atoms attached) to attack genes, which turns them off or mutes them, at a time when they should be turned on. When genes are turned off, they can’t direct the manufacture of proteins that are essential for proper cell function. Chemicals also can uncoil parts of the chromosome, causing genes to be expressed, or turned on, at inappropriate times.
An example is asthmatic children. Wan-Yee Tang, a researcher at the University of Cincinnati, found that children in New York City exposed in the womb to high levels of polycyclic aromatic hydrocarbons (PAHs), common air pollutants from traffic, were much more likely to have asthma than those who were not exposed. By studying cord blood, she found that a particular gene (ACSL3) was methylated in the asthmatic children and unmethylated in the unexposed children, and concluded that the abnormal methylation patterns probably caused the asthma.
The finding could in part explain why worldwide asthma rates have skyrocketed in much of the world, reaching epidemic proportions among children. In the boroughs of New York City with the worst air pollution, about 25 percent of children are asthmatic.
Epigenetic changes also have been observed in children conceived with assisted reproductive technologies, said Richard Meehan of the Medical Research Council in Scotland.
One of the disorders that occurs at a higher rate in these children is Beckwith-Wiedemann syndrome, which is characterized by abdominal wall defects and a higher risk of certain childhood cancers. The culture medium where fertilized eggs are grown for several days before implantation probably causes the syndrome, he said. It appears that all the different media used for the eggs might be problematic because they contain chemicals that stimulate the addition of methyl groups to the cells.
The scientists at the workshop said it’s important to understand epigenetics not only to figure out which chemicals might endanger public health, but to find new ways to prevent or treat diseases.
Scientists are just now beginning to figure out normal methylation patterns in the genome so they can learn what is abnormal, said Karl T. Kelsey, professor of community heath and pathology at Brown University in Rhode Island. As a result of this new understanding, epigenetic therapies have been developed for some types of cancers, and some have been successful in clinical trials, he said. Unlike traditional cancer drugs, which kill cells, the new drugs simply change how the cells act.
Research with rats shows that gene-altering chemicals can change animals’ brains—in some cases, in a beneficial way.
Moshe Szyf, a pharmacology and therapeutics professor at McGill University Medical School in Montreal, found that rats that received healthy doses of maternal licking as pups grew up to be calmer than pups who had inattentive mothers. The maternal grooming brought about a chemical change in the part of the pup’s brain that produces stress hormones, he said.
The rats reared by attentive mothers had different levels of corticoid gene expression and lower levels of stress hormones than those reared by inattentive mothers. Szyf found he could cure the stressed rats by injecting a chemical called TSA into their brains, which reversed the inappropriate methylation caused by inattentive mothering.
This understanding of epigenetics may lead to new medications for treating human problems. By using approaches similar to those used in the rat study, Szyf is hoping to find drugs that will help alleviate human psychiatric conditions.
Szyf also studied the preserved brains of suicide victims and of people who died suddenly from causes other than suicide. He found that certain genes in the suicide victims were methylated, or turned off. In contrast, those same genes were not methylated in the victims who died by other means. Abnormal methylation patterns could cause depression in some people, he said.
Some compounds, such as nickel, chromium and arsenic, are well-known carcinogens—not because they are toxic to cells but because of their epigenetic effect, said Max Costa, a New York University professor of environmental medicine and pharmacology. They increase DNA methylation, which results in gene silencing and cell transformation and leads to cancer, he explained.
Researchers at the meeting spent a great deal of time discussing whether and how to test chemicals for their ability to cause epigenetic changes.
Most researchers there agreed that compounds need to be tested for epigenetic effects. But practical testing of the 80,000 or so chemicals in commerce would require rapid screens that would prioritize the compounds into high, medium, and low-risk groups. Those at high risk for epigenetic effects could then be subjected to more definitive and expensive tests.
John M. Greally, associate professor at the Albert Einstein College of Medicine in New York City, pointed out that no single test is ideal for detecting epigenetic effects.
“All of the assays have drawbacks,” he said. For example, one assay requires immediate sample processing so it cannot be used on stored samples.
Nevertheless, many researchers said that testing chemicals for epigenetic changes can begin soon.
“The fact that we don’t know a great deal about this area doesn’t mean it’s daunting,” said George Daston, research fellow at Procter & Gamble. “We just need to build on what we have. Microassays already show how chemical exposures change the gene expression in certain parts of the genome. The fact that we don’t know a lot doesn’t mean we can’t start testing quickly.”
Birnbaum, who formerly was head of experimental toxicology at the U.S. Environmental Protection Agency, said regulators and industry don’t have to start from square one.
“We’re already marching down this road,” said Birnbaum. “The National Toxicology Program is already talking about including some epigenetic studies in the program.”
The most important public health issue that arises from epigenetics, Birnbaum told Environmental Health News, is that the current environment may not be the crucial factor to consider when examining what causes diseases.
“Asking heart attack victims what they ate this year or last may be far less important than what they were exposed to in the womb and shortly after birth,” she said.
Last week, several dozen researchers and experts convened by the National Academies tackled this complicated topic, called epigenetics, at a two-day workshop in Washington, D.C. They discussed new findings that suggest chemicals in our environment and in our food can alter genes, leaving people vulnerable to a variety of diseases and disorders, including diabetes, asthma, cancer and obesity. They also considered whether regulatory agencies and industry should start testing the thousands of chemicals in use today for these effects.
“There is little doubt these epigenetic effects are important. The next question is how we test for effects," said William H. Farland, professor of environmental and radiological health sciences at Colorado State University. "We don’t need to abandon current approaches to chemical testing. When testing chemicals in animals, we may just need to add some new endpoints."
Linda S. Birnbaum, Director of the National Institute of Environmental Health Sciences
Exposure to gene-altering substances, particularly in the womb and shortly after birth, “can lead to increased susceptibility to disease,” said Linda S. Birnbaum, who was named director of the National Institute of Environmental Health Sciences and of the National Toxicology Program in December. “The susceptibility persists long after the exposure is gone, even decades later. Glands, organs, and systems can be permanently altered.”
Animal studies indicate that some environmental chemicals cause epigenetic changes that trigger breast and prostate cancer, obesity, diabetes, heart disease, asthma, Alzheimer’s, Parkinson’s disease and learning disabilities, she said. And some new human studies are now adding to the evidence.
“There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and grandmother were exposed to during pregnancy,” Birnbaum said. “There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and grandmother were exposed to during pregnancy.” Linda Birnbaum, Director, National Institute of Environmental Health Sciences
What a pregnant mother eats and the chemicals she is exposed to can affect her offspring without causing mutations in the DNA, the experts said. Instead, such exposures can disrupt the way that genes behave, according to both animal and human studies. These changes, in turn, can be passed on to the next generations.
Some environmental chemicals enable methyl groups (carbon atoms with three hydrogen atoms attached) to attack genes, which turns them off or mutes them, at a time when they should be turned on. When genes are turned off, they can’t direct the manufacture of proteins that are essential for proper cell function. Chemicals also can uncoil parts of the chromosome, causing genes to be expressed, or turned on, at inappropriate times.
An example is asthmatic children. Wan-Yee Tang, a researcher at the University of Cincinnati, found that children in New York City exposed in the womb to high levels of polycyclic aromatic hydrocarbons (PAHs), common air pollutants from traffic, were much more likely to have asthma than those who were not exposed. By studying cord blood, she found that a particular gene (ACSL3) was methylated in the asthmatic children and unmethylated in the unexposed children, and concluded that the abnormal methylation patterns probably caused the asthma.
The finding could in part explain why worldwide asthma rates have skyrocketed in much of the world, reaching epidemic proportions among children. In the boroughs of New York City with the worst air pollution, about 25 percent of children are asthmatic.
Epigenetic changes also have been observed in children conceived with assisted reproductive technologies, said Richard Meehan of the Medical Research Council in Scotland.
One of the disorders that occurs at a higher rate in these children is Beckwith-Wiedemann syndrome, which is characterized by abdominal wall defects and a higher risk of certain childhood cancers. The culture medium where fertilized eggs are grown for several days before implantation probably causes the syndrome, he said. It appears that all the different media used for the eggs might be problematic because they contain chemicals that stimulate the addition of methyl groups to the cells.
The scientists at the workshop said it’s important to understand epigenetics not only to figure out which chemicals might endanger public health, but to find new ways to prevent or treat diseases.
Scientists are just now beginning to figure out normal methylation patterns in the genome so they can learn what is abnormal, said Karl T. Kelsey, professor of community heath and pathology at Brown University in Rhode Island. As a result of this new understanding, epigenetic therapies have been developed for some types of cancers, and some have been successful in clinical trials, he said. Unlike traditional cancer drugs, which kill cells, the new drugs simply change how the cells act.
Research with rats shows that gene-altering chemicals can change animals’ brains—in some cases, in a beneficial way.
Moshe Szyf, a pharmacology and therapeutics professor at McGill University Medical School in Montreal, found that rats that received healthy doses of maternal licking as pups grew up to be calmer than pups who had inattentive mothers. The maternal grooming brought about a chemical change in the part of the pup’s brain that produces stress hormones, he said.
The rats reared by attentive mothers had different levels of corticoid gene expression and lower levels of stress hormones than those reared by inattentive mothers. Szyf found he could cure the stressed rats by injecting a chemical called TSA into their brains, which reversed the inappropriate methylation caused by inattentive mothering.
This understanding of epigenetics may lead to new medications for treating human problems. By using approaches similar to those used in the rat study, Szyf is hoping to find drugs that will help alleviate human psychiatric conditions.
Szyf also studied the preserved brains of suicide victims and of people who died suddenly from causes other than suicide. He found that certain genes in the suicide victims were methylated, or turned off. In contrast, those same genes were not methylated in the victims who died by other means. Abnormal methylation patterns could cause depression in some people, he said.
Some compounds, such as nickel, chromium and arsenic, are well-known carcinogens—not because they are toxic to cells but because of their epigenetic effect, said Max Costa, a New York University professor of environmental medicine and pharmacology. They increase DNA methylation, which results in gene silencing and cell transformation and leads to cancer, he explained.
Researchers at the meeting spent a great deal of time discussing whether and how to test chemicals for their ability to cause epigenetic changes.
Most researchers there agreed that compounds need to be tested for epigenetic effects. But practical testing of the 80,000 or so chemicals in commerce would require rapid screens that would prioritize the compounds into high, medium, and low-risk groups. Those at high risk for epigenetic effects could then be subjected to more definitive and expensive tests.
John M. Greally, associate professor at the Albert Einstein College of Medicine in New York City, pointed out that no single test is ideal for detecting epigenetic effects.
“All of the assays have drawbacks,” he said. For example, one assay requires immediate sample processing so it cannot be used on stored samples.
Nevertheless, many researchers said that testing chemicals for epigenetic changes can begin soon.
“The fact that we don’t know a great deal about this area doesn’t mean it’s daunting,” said George Daston, research fellow at Procter & Gamble. “We just need to build on what we have. Microassays already show how chemical exposures change the gene expression in certain parts of the genome. The fact that we don’t know a lot doesn’t mean we can’t start testing quickly.”
Birnbaum, who formerly was head of experimental toxicology at the U.S. Environmental Protection Agency, said regulators and industry don’t have to start from square one.
“We’re already marching down this road,” said Birnbaum. “The National Toxicology Program is already talking about including some epigenetic studies in the program.”
The most important public health issue that arises from epigenetics, Birnbaum told Environmental Health News, is that the current environment may not be the crucial factor to consider when examining what causes diseases.
“Asking heart attack victims what they ate this year or last may be far less important than what they were exposed to in the womb and shortly after birth,” she said.
What a pregnant mother eats and the chemicals she is exposed to can affect her offspring without causing mutations in the DNA, the experts said. Instead, such exposures can disrupt the way that genes behave, according to both animal and human studies. These changes, in turn, can be passed on to the next generations.
Some environmental chemicals enable methyl groups (carbon atoms with three hydrogen atoms attached) to attack genes, which turns them off or mutes them, at a time when they should be turned on. When genes are turned off, they can’t direct the manufacture of proteins that are essential for proper cell function. Chemicals also can uncoil parts of the chromosome, causing genes to be expressed, or turned on, at inappropriate times.
An example is asthmatic children. Wan-Yee Tang, a researcher at the University of Cincinnati, found that children in New York City exposed in the womb to high levels of polycyclic aromatic hydrocarbons (PAHs), common air pollutants from traffic, were much more likely to have asthma than those who were not exposed. By studying cord blood, she found that a particular gene (ACSL3) was methylated in the asthmatic children and unmethylated in the unexposed children, and concluded that the abnormal methylation patterns probably caused the asthma.
The finding could in part explain why worldwide asthma rates have skyrocketed in much of the world, reaching epidemic proportions among children. In the boroughs of New York City with the worst air pollution, about 25 percent of children are asthmatic.
Epigenetic changes also have been observed in children conceived with assisted reproductive technologies, said Richard Meehan of the Medical Research Council in Scotland.
One of the disorders that occurs at a higher rate in these children is Beckwith-Wiedemann syndrome, which is characterized by abdominal wall defects and a higher risk of certain childhood cancers. The culture medium where fertilized eggs are grown for several days before implantation probably causes the syndrome, he said. It appears that all the different media used for the eggs might be problematic because they contain chemicals that stimulate the addition of methyl groups to the cells.
The scientists at the workshop said it’s important to understand epigenetics not only to figure out which chemicals might endanger public health, but to find new ways to prevent or treat diseases.
Scientists are just now beginning to figure out normal methylation patterns in the genome so they can learn what is abnormal, said Karl T. Kelsey, professor of community heath and pathology at Brown University in Rhode Island. As a result of this new understanding, epigenetic therapies have been developed for some types of cancers, and some have been successful in clinical trials, he said. Unlike traditional cancer drugs, which kill cells, the new drugs simply change how the cells act.
Research with rats shows that gene-altering chemicals can change animals’ brains—in some cases, in a beneficial way.
Moshe Szyf, a pharmacology and therapeutics professor at McGill University Medical School in Montreal, found that rats that received healthy doses of maternal licking as pups grew up to be calmer than pups who had inattentive mothers. The maternal grooming brought about a chemical change in the part of the pup’s brain that produces stress hormones, he said.
The rats reared by attentive mothers had different levels of corticoid gene expression and lower levels of stress hormones than those reared by inattentive mothers. Szyf found he could cure the stressed rats by injecting a chemical called TSA into their brains, which reversed the inappropriate methylation caused by inattentive mothering.
This understanding of epigenetics may lead to new medications for treating human problems. By using approaches similar to those used in the rat study, Szyf is hoping to find drugs that will help alleviate human psychiatric conditions.
Szyf also studied the preserved brains of suicide victims and of people who died suddenly from causes other than suicide. He found that certain genes in the suicide victims were methylated, or turned off. In contrast, those same genes were not methylated in the victims who died by other means. Abnormal methylation patterns could cause depression in some people, he said.
Some compounds, such as nickel, chromium and arsenic, are well-known carcinogens—not because they are toxic to cells but because of their epigenetic effect, said Max Costa, a New York University professor of environmental medicine and pharmacology. They increase DNA methylation, which results in gene silencing and cell transformation and leads to cancer, he explained.
Researchers at the meeting spent a great deal of time discussing whether and how to test chemicals for their ability to cause epigenetic changes.
Most researchers there agreed that compounds need to be tested for epigenetic effects. But practical testing of the 80,000 or so chemicals in commerce would require rapid screens that would prioritize the compounds into high, medium, and low-risk groups. Those at high risk for epigenetic effects could then be subjected to more definitive and expensive tests.
John M. Greally, associate professor at the Albert Einstein College of Medicine in New York City, pointed out that no single test is ideal for detecting epigenetic effects.
“All of the assays have drawbacks,” he said. For example, one assay requires immediate sample processing so it cannot be used on stored samples.
Nevertheless, many researchers said that testing chemicals for epigenetic changes can begin soon.
“The fact that we don’t know a great deal about this area doesn’t mean it’s daunting,” said George Daston, research fellow at Procter & Gamble. “We just need to build on what we have. Microassays already show how chemical exposures change the gene expression in certain parts of the genome. The fact that we don’t know a lot doesn’t mean we can’t start testing quickly.”
Birnbaum, who formerly was head of experimental toxicology at the U.S. Environmental Protection Agency, said regulators and industry don’t have to start from square one.
“We’re already marching down this road,” said Birnbaum. “The National Toxicology Program is already talking about including some epigenetic studies in the program.”
The most important public health issue that arises from epigenetics, Birnbaum told Environmental Health News, is that the current environment may not be the crucial factor to consider when examining what causes diseases.
“Asking heart attack victims what they ate this year or last may be far less important than what they were exposed to in the womb and shortly after birth,” she said.
Metal leak at China chemical plant leaves 500 sick
More than 500 villagers in central China have been found to have high concentrations of a dangerous metal in their bodies after a series of leaks from a chemical plant, state media reported Monday.
Of the nearly 3,000 villagers living near the Changsha Xianghe Chemical Plant in Hunan province's Zhentou township, 509 people were found to have high concentrations of cadmium and 33 were hospitalized over the weekend, according to the official Xinhua News Agency. Cadmium is used to make batteries.
The chemicals may have been leaking for months before two villagers, since found to have excessive levels of cadmium, died in May and June.
Two senior environmental officials were suspended and the head of the chemical plant was detained Saturday. That followed protests last week by nearly 1,000 residents complaining that deadly pollutants were being discharged from the factory into water that irrigates rice and vegetable fields, according to Xinhua.
Calls to the Liuyang city government office rang unanswered late Monday.
Factory accidents and chemical leaks are common in China, in part because of lax enforcement of proper worker training and safety rules.
Exposure to large amounts of cadmium can cause failure of the central nervous system and lungs, lead to severe brain damage and in some cases, cause death.
China's waterways, especially its major rivers, are dangerously polluted after decades of rapid economic growth and poor enforcement of pollution controls.
Of the nearly 3,000 villagers living near the Changsha Xianghe Chemical Plant in Hunan province's Zhentou township, 509 people were found to have high concentrations of cadmium and 33 were hospitalized over the weekend, according to the official Xinhua News Agency. Cadmium is used to make batteries.
The chemicals may have been leaking for months before two villagers, since found to have excessive levels of cadmium, died in May and June.
Two senior environmental officials were suspended and the head of the chemical plant was detained Saturday. That followed protests last week by nearly 1,000 residents complaining that deadly pollutants were being discharged from the factory into water that irrigates rice and vegetable fields, according to Xinhua.
Calls to the Liuyang city government office rang unanswered late Monday.
Factory accidents and chemical leaks are common in China, in part because of lax enforcement of proper worker training and safety rules.
Exposure to large amounts of cadmium can cause failure of the central nervous system and lungs, lead to severe brain damage and in some cases, cause death.
China's waterways, especially its major rivers, are dangerously polluted after decades of rapid economic growth and poor enforcement of pollution controls.
Alaska's biggest tundra fire sparks climate warning
The fire that raged north of Alaska's Brooks mountain range in 2007 left a 1000-square-kilometre scorched patch of earth – an area larger than the sum of all known fires on Alaska's North Slope since 1950.
Now scientists studying the ecological impact of the fire report that the blaze dumped 1.3 million tonnes of carbon dioxide into the atmosphere – about the amount that Barbados puts out in a year. What's more, at next week's meeting of the Ecological Society of America in Albuquerque, New Mexico, two teams will warn that as climate change takes hold tundra fires across the Arctic will become more frequent.
Tundra fires only take off once certain thresholds are reached, says Adrian Rocha of the Marine Biological Laboratory, Woods Hole, Massachusetts. "But projected changes in climate over the next century – increased aridity, thunderstorms, and warming in the Arctic – will increase the likelihood that these thresholds will be crossed and thus result in more larger and frequent fires."
Scarred surface
Rocha's team placed carbon dioxide and radiation sensors across the fire-scar and found that in the year after the fire, the most severely burned tundra emitted twice as much carbon as undamaged tundra normally stores away.
Pristine tundra takes up about 30 to 70 grams of carbon per square metre during the summer months, whereas the severely burned site lost about 40 to 120 grams per square metre. The team also found that the most severely burned terrain absorbed 71 per cent more solar radiation than normal, warming faster as a result and losing a layer of permafrost 5 to 10 centimetres deep.
"That may not seem like a lot," says Rocha, "but over the entire fire scar you're talking about 5 to 10 cm of water over a 1000 sq km area." Plus there's the double whammy of positive feedback: as tundra burns and emits carbon, it melts the permafrost – and that releases more carbon into the atmosphere. "Along with the melting ice in the permafrost, you're also exposing more old carbon that was stored in that freezer [as organic material] and is being allowed to decompose and reintroduce itself to the atmosphere."
Another team, led by Michelle Mack of the University of Florida, carbon-dated soil at the most severely burned sites. They found that organic matter accumulated over 50 years had been lost.
Long-term impact
Wetland ecologist William Bowden of the University of Vermont, Burlington, not at the ESA meeting, says that the fire blackened the surface and increased the amount of water in the soil. "Both factors should promote soil warming, permafrost thaw, and possible thermokarst formation," he says.
Thermokasts are areas of collapsed terrain where structurally important permafrost has thawed – a process that can damage the foundations of homes, roads, and pipelines. Permafrost melt will also increase the amount of greenhouse gases such as methane entering the atmosphere.
There are great similarities between plants and soils across the Arctic, adds Bowden, and lessons learned in Alaska are relevant to similar terrains in Canada and Russia.
Now scientists studying the ecological impact of the fire report that the blaze dumped 1.3 million tonnes of carbon dioxide into the atmosphere – about the amount that Barbados puts out in a year. What's more, at next week's meeting of the Ecological Society of America in Albuquerque, New Mexico, two teams will warn that as climate change takes hold tundra fires across the Arctic will become more frequent.
Tundra fires only take off once certain thresholds are reached, says Adrian Rocha of the Marine Biological Laboratory, Woods Hole, Massachusetts. "But projected changes in climate over the next century – increased aridity, thunderstorms, and warming in the Arctic – will increase the likelihood that these thresholds will be crossed and thus result in more larger and frequent fires."
Scarred surface
Rocha's team placed carbon dioxide and radiation sensors across the fire-scar and found that in the year after the fire, the most severely burned tundra emitted twice as much carbon as undamaged tundra normally stores away.
Pristine tundra takes up about 30 to 70 grams of carbon per square metre during the summer months, whereas the severely burned site lost about 40 to 120 grams per square metre. The team also found that the most severely burned terrain absorbed 71 per cent more solar radiation than normal, warming faster as a result and losing a layer of permafrost 5 to 10 centimetres deep.
"That may not seem like a lot," says Rocha, "but over the entire fire scar you're talking about 5 to 10 cm of water over a 1000 sq km area." Plus there's the double whammy of positive feedback: as tundra burns and emits carbon, it melts the permafrost – and that releases more carbon into the atmosphere. "Along with the melting ice in the permafrost, you're also exposing more old carbon that was stored in that freezer [as organic material] and is being allowed to decompose and reintroduce itself to the atmosphere."
Another team, led by Michelle Mack of the University of Florida, carbon-dated soil at the most severely burned sites. They found that organic matter accumulated over 50 years had been lost.
Long-term impact
Wetland ecologist William Bowden of the University of Vermont, Burlington, not at the ESA meeting, says that the fire blackened the surface and increased the amount of water in the soil. "Both factors should promote soil warming, permafrost thaw, and possible thermokarst formation," he says.
Thermokasts are areas of collapsed terrain where structurally important permafrost has thawed – a process that can damage the foundations of homes, roads, and pipelines. Permafrost melt will also increase the amount of greenhouse gases such as methane entering the atmosphere.
There are great similarities between plants and soils across the Arctic, adds Bowden, and lessons learned in Alaska are relevant to similar terrains in Canada and Russia.
Sunday, August 2, 2009
India looks to the sun for ambitious surge in green power
For centuries Hindus have revered the sun god, Surya, as a source of health and prosperity, building lavish temples and holding festivals in his honour across a country with more than 300 days of sunshine a year.
Now India is putting its faith in the sun in a more literal sense by revealing what experts describe as the world’s most ambitious plan to develop solar energy over the next three or four decades.
Manmohan Singh, the Prime Minister, will chair a meeting today to decide whether to approve a National Solar Mission designed to curb India’s carbon emissions and ease its crippling power shortages. It proposes boosting India’s solar power generation capacity from almost zero to 20 gigawatts (20 billion watts) by 2020, 100GW by 2030 and 200GW by 2050, according to a draft seen by The Times. The entire world can generate about 14GW of solar power today.
India’s plan also proposes reducing the price of solar power to the same level as that from fossil fuels by 2020, according to the draft, dated April 29. Solar power in India currently costs about 15 rupees (20p) per kWh, compared with an average 3.5 rupees per kWh for electricity from the national grid, which is largely produced by coal-fired thermal power plants.
Other targets include forcing all government buildings to have solar panels by 2012 and developing micro-financing to encourage 20 million households to install solar lighting by 2020. The plan also outlines a system — similar to Germany’s — of paying households for any surplus power from solar panels fed back into the grid.
To achieve these and other goals, the mission proposes that the Government invest 920 billion rupees (£11.5 billion) in developing, manufacturing and installing solar technology over the next 30 years.
The mission is primarily designed to improve India’s energy security as it has abundant supplies of coal — the dirtiest of the fossil fuels — but has to import 70 per cent of its crude oil and half its natural gas. It is also meant to ease a chronic power shortage that has left 400 million Indians without electricity, causes daily blackouts in cities, and represents one of the biggest obstacles to economic growth.
India now has the capacity to produce 150GW — less than a fifth of China’s — and demand outstripped supply by 9.5 per cent between 2008-09, and by 13.8 per cent during peak hours, according to the Power Ministry. Indian officials also hope that the mission will help to ease the pressure from Western governments at international talks for a new UN climate pact in December.
Environmental campaigners have welcomed the plan, saying that solar energy is India’s most realistic alternative power source, as it does not have the space for large wind plants. Siddharth Pathak, chief climate change campaigner for Greenpeace in India, said: “India’s putting a very strong argument in front of developed countries that it has huge potential for renewable energy.” However, some government officials remain sceptical about risking so much money on new technology, rather than spending it on providing all Indians with electricity from conventional sources
Now India is putting its faith in the sun in a more literal sense by revealing what experts describe as the world’s most ambitious plan to develop solar energy over the next three or four decades.
Manmohan Singh, the Prime Minister, will chair a meeting today to decide whether to approve a National Solar Mission designed to curb India’s carbon emissions and ease its crippling power shortages. It proposes boosting India’s solar power generation capacity from almost zero to 20 gigawatts (20 billion watts) by 2020, 100GW by 2030 and 200GW by 2050, according to a draft seen by The Times. The entire world can generate about 14GW of solar power today.
India’s plan also proposes reducing the price of solar power to the same level as that from fossil fuels by 2020, according to the draft, dated April 29. Solar power in India currently costs about 15 rupees (20p) per kWh, compared with an average 3.5 rupees per kWh for electricity from the national grid, which is largely produced by coal-fired thermal power plants.
Other targets include forcing all government buildings to have solar panels by 2012 and developing micro-financing to encourage 20 million households to install solar lighting by 2020. The plan also outlines a system — similar to Germany’s — of paying households for any surplus power from solar panels fed back into the grid.
To achieve these and other goals, the mission proposes that the Government invest 920 billion rupees (£11.5 billion) in developing, manufacturing and installing solar technology over the next 30 years.
The mission is primarily designed to improve India’s energy security as it has abundant supplies of coal — the dirtiest of the fossil fuels — but has to import 70 per cent of its crude oil and half its natural gas. It is also meant to ease a chronic power shortage that has left 400 million Indians without electricity, causes daily blackouts in cities, and represents one of the biggest obstacles to economic growth.
India now has the capacity to produce 150GW — less than a fifth of China’s — and demand outstripped supply by 9.5 per cent between 2008-09, and by 13.8 per cent during peak hours, according to the Power Ministry. Indian officials also hope that the mission will help to ease the pressure from Western governments at international talks for a new UN climate pact in December.
Environmental campaigners have welcomed the plan, saying that solar energy is India’s most realistic alternative power source, as it does not have the space for large wind plants. Siddharth Pathak, chief climate change campaigner for Greenpeace in India, said: “India’s putting a very strong argument in front of developed countries that it has huge potential for renewable energy.” However, some government officials remain sceptical about risking so much money on new technology, rather than spending it on providing all Indians with electricity from conventional sources
Bubbles of warming, beneath the ice
Four miles south of the Arctic Circle, the morning sky is streaked with apricot. Frozen rivers split the tundra of the Seward Peninsula, coiling into vast lakes. And on a silent, wind-whipped pond, a lone figure, sweating and panting, shovels snow off the ice.
The young woman with curly reddish hair stops, scribbles data, snaps a photo, grabs a heavy metal pick and stabs at white orbs in the thick black ice.
"Every time I see bubbles, I have the same feeling," says Katey Walter, a University of Alaska researcher. "They are amazing and beautiful."
Beautiful, yes. But ominous. When her pick breaks through the surface, the orbs burst with a low gurgle, spewing methane, a potent greenhouse gas that could accelerate the pace of climate change across the globe.
International experts are alarmed. "Methane release due to thawing permafrost in the Arctic is a global warming wild card," warned a report by the United Nations Environment Program last year. Large amounts entering the atmosphere, it concluded, could lead to "abrupt changes in the climate that would likely be irreversible."
Methane (CH4) has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide (CO2). As warmer air thaws Arctic soils, as much as 55 billion tons of methane could be released from beneath Siberian lakes alone, according to Walter’s research. That would amount to 10 times the amount currently in the atmosphere.
At 32, Walter, an aquatic ecologist, is a rising star among the thousands of scientists who are struggling to map, measure and predict climate change. Parts of her doctoral dissertation on Siberian lakes were published in three prestigious journals in 2007: Science, Nature and Philosophical Transactions of the Royal Society.
According to one of her studies, methane emissions from Arctic lakes were a major contributor to a period of global warming more than 11,000 years ago.
"It happened on a large scale in the past, and it could happen on a large scale in the future," says Walter, who refers to potential methane emissions as "a time bomb."
Methane levels in the atmosphere have tripled since preindustrial times. Human activities, including rice cultivation, cattle raising and coal mining, account for about 70% of releases, according to recent studies. Natural sources, like tropical wetlands and termites, make up the rest. But those estimates had not incorporated the bubbles Walter was probing on an autumn morning on the Seward Peninsula.
That gurgling gas could change the entire model for predicting global warming. And lakes are not the only methane source: Newly discovered seeps -- places where methane leaks to the surface -- from the shallow waters of Siberia's vast continental shelf are also likely to upset previous assumptions.
Walter's work "has gotten a lot of attention," said John E. Walsh, chief scientist of the International Arctic Research Center in Fairbanks. "She found direct evidence of methane releases in high-latitude lakes. That was not fully realized before."
In a field where the science often seems opaque, Walter's research has a flashy side. She enjoys igniting methane seeps with a cigarette lighter, leaping away as the gas flares as high as 20 feet.
"It's fun," she says. "And it is informative."
Videos of the stunts have swept through the Internet, rare visual evidence of possible danger ahead. At a recent Senate hearing, Al Gore played a clip of her lighting a methane seep. The BBC, the Discovery Channel and the History Channel have featured her in documentaries.
But the complex science of Arctic methane is only beginning to be understood. In the desolate wilderness of the Bering Land Bridge National Preserve, a sense of urgency is palpable among Walter and three fellow researchers, hunkered down in neon-orange tents.
An occasional helicopter ferries supplies from Nome, the closest town, soaring over scattered herds of caribou. A red fox scampers through the brush. Across a snowfield, bear tracks recede into the distance, a reminder that field science isn't for sissies.
"Can you shoot a gun?" Walter asks a visitor, as she heads out to one of 20 lakes she is surveying. When the answer is noncommittal, she hands over bear spray and instructs: "Don't use it until the bear is right up close, facing you."
Nowhere is the evidence of a heating planet more dramatic than in the polar regions. Over the last 50 years, the Arctic has warmed twice as fast as the rest of the globe. Last summer, for the first time in recorded history, the North Pole could be circumnavigated. Ice sheets on Greenland and West Antarctica are melting rapidly. Polar bears and emperor penguins are threatened with extinction.
Even as glaciers and sea ice have captured the most headlines, growing concern is now focused on the transformation of permafrost, soils that are frozen year-round
Today, 20% of Earth's land surface is locked up in a deep freeze. But scientists predict that air temperature in the Arctic is likely to rise as much as 6 degrees Celsius, or 10.8 degrees Fahrenheit, by the end of the century. That is expected to boost the emission of carbon compounds from soils.
The upper 3 meters -- about 10 feet -- of permafrost stores 1.9 trillion tons of carbon, more than double the amount in the atmosphere today, according to a recent study in the journal Bioscience.
"We are seeing thawing down to 5 meters," says geophysicist Vladimir Romanovsky of the University of Alaska. "A third to a half of permafrost is already within a degree to a degree and a half [Celsius] of thawing."
If only 1% of permafrost carbon were to be released each year, that could double the globe's annual carbon emissions, Romanovsky notes. "We are at a tipping point for positive feedback," he warns, referring to a process in which warming spurs emissions, which in turn generate more heat, in an uncontrollable cycle.
Walter's work is crucial, according to Romanovsky and others, because global warming hinges partly on the ratio of how much carbon is released as CO2 versus how much as methane, a molecule that contains both carbon and hydrogen. Methane, although a far more potent greenhouse gas than carbon dioxide, breaks down more quickly. But when it does, it oxidizes into a carbon dioxide molecule, which can last more than a century in the atmosphere.
Out on the lake, Walter explains: When organic matter (dead plants and animals) rots in the ground, it gives off carbon dioxide. Much of the organic material of thawed permafrost is expected to release carbon dioxide.
But as ice inside permafrost melts, small sinkholes open in the ground and fill with water, joining together to form millions of ponds and lakes. Organic matter slips from eroding shorelines to lake bottoms, where microbes feed on it. Because lake bottoms are oxygen-free, the microbes generate methane in addition to carbon dioxide -- as in the burping La Brea tar pits.
"These lakes are getting bigger -- in some places by a meter a year," Walter says, scooping out slush from the hole she has punched through 6 inches of ice. Into the seep, she inserts a plastic umbrella-like contraption fitted with a bottle to collect gas and a suspended brick to hold it straight.
Before Walter perfected the methane trap, when she was a graduate student in Siberia, she would swim in near-freezing water, dodging leeches and muskrats. Once she caught pneumonia. Another time, her hair caught on fire as she ignited a methane seep.
On the Seward Peninsula trip, she hikes up to 8 miles a day from lake to lake through snowdrifts. Her hip is black and blue from a fall through the ice. "Methane is hard work," she says with a smile.
At each seep, Walter places a small red flag so her colleagues can find the bubbles. Lawrence Plug, a geophysicist from Dalhousie University in Halifax, Canada; Guido Grosse, a German geologist; and Benjamin M. Jones, a U.S. Geological Survey researcher, help shovel off the ice in straight-line paths, take notes on the size of each bubble group, record the location with global positioning system devices, and measure the depth of the lakes.
In the evening, in a cramped cook tent, jars of peanut butter and Nutella sit amid satellite data maps and a textbook on "Applied Linear Statistical Models." Frosted hats and mittens drip from a clothesline. Jones cooks up a batch of hamburger as Walter labels methane bottles with a marker and enters data into her laptop.
Over the next two years, the researchers, funded by the National Science Foundation and NASA, will move between Siberia and Alaska. They will drill permafrost cores, map seeps and analyze data to produce a model of how methane from Arctic lakes might affect Earth's future climate.
"By figuring out how quickly permafrost thawed in the past, we can test our models to predict how fast it could thaw in the next 100 years," says Plug, who will make the complex calculations. "If the temperature warms a couple of degrees Celsius, the lakes could expand at two or three times their current rate."
Elsewhere, scientists cast a wary eye toward clouds of methane bubbles roiling the waters of the Siberian continental shelf. Those emissions, possibly from subsurface permafrost, are even harder to measure than lake emissions.
Meanwhile, researchers are debating the possibility of eventual seeps from methane hydrates -- icy formations beneath the continental shelves and the ocean bottom, and far below land-based permafrost.
Walsh, at the International Arctic Research Center, emphasizes the "huge range of uncertainty" as to how much climate change methane emissions could trigger. "The potential is there for large releases. But there is also a risk of alarmism."
To many Alaskans, it is hardly news that permafrost is thawing: Across the state, houses have been collapsing and trees tipping over. Researchers estimate that repairing affected schools, roads and bridges will cost up to $6 billion over the next two decades.
But the global implications have yet to sink in.
Out on the wild frontier of climate research, far from the legislatures and the diplomatic gatherings where climate policy is debated, Katey Walter and her colleagues focus on what they call "ground truthing."
And beyond that laborious data-gathering, Walter has a mission: to spread the word about what is happening. At the beginning of her field trip, she stops in Nome and leads a group of fifth-graders, many from Alaska Native tribes, out to poke holes in the ice of a nearby lake and light methane flares.
She talks to them about people who live in faraway cities, driving automobiles and working in industries that emit carbon dioxide. And how that causes warming that is felt in the Arctic. And why, even though there are so few people in Alaska, the ice around them is melting.
"That's what we're studying," she explains. "It's all related."
The young woman with curly reddish hair stops, scribbles data, snaps a photo, grabs a heavy metal pick and stabs at white orbs in the thick black ice.
"Every time I see bubbles, I have the same feeling," says Katey Walter, a University of Alaska researcher. "They are amazing and beautiful."
Beautiful, yes. But ominous. When her pick breaks through the surface, the orbs burst with a low gurgle, spewing methane, a potent greenhouse gas that could accelerate the pace of climate change across the globe.
International experts are alarmed. "Methane release due to thawing permafrost in the Arctic is a global warming wild card," warned a report by the United Nations Environment Program last year. Large amounts entering the atmosphere, it concluded, could lead to "abrupt changes in the climate that would likely be irreversible."
Methane (CH4) has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide (CO2). As warmer air thaws Arctic soils, as much as 55 billion tons of methane could be released from beneath Siberian lakes alone, according to Walter’s research. That would amount to 10 times the amount currently in the atmosphere.
At 32, Walter, an aquatic ecologist, is a rising star among the thousands of scientists who are struggling to map, measure and predict climate change. Parts of her doctoral dissertation on Siberian lakes were published in three prestigious journals in 2007: Science, Nature and Philosophical Transactions of the Royal Society.
According to one of her studies, methane emissions from Arctic lakes were a major contributor to a period of global warming more than 11,000 years ago.
"It happened on a large scale in the past, and it could happen on a large scale in the future," says Walter, who refers to potential methane emissions as "a time bomb."
Methane levels in the atmosphere have tripled since preindustrial times. Human activities, including rice cultivation, cattle raising and coal mining, account for about 70% of releases, according to recent studies. Natural sources, like tropical wetlands and termites, make up the rest. But those estimates had not incorporated the bubbles Walter was probing on an autumn morning on the Seward Peninsula.
That gurgling gas could change the entire model for predicting global warming. And lakes are not the only methane source: Newly discovered seeps -- places where methane leaks to the surface -- from the shallow waters of Siberia's vast continental shelf are also likely to upset previous assumptions.
Walter's work "has gotten a lot of attention," said John E. Walsh, chief scientist of the International Arctic Research Center in Fairbanks. "She found direct evidence of methane releases in high-latitude lakes. That was not fully realized before."
In a field where the science often seems opaque, Walter's research has a flashy side. She enjoys igniting methane seeps with a cigarette lighter, leaping away as the gas flares as high as 20 feet.
"It's fun," she says. "And it is informative."
Videos of the stunts have swept through the Internet, rare visual evidence of possible danger ahead. At a recent Senate hearing, Al Gore played a clip of her lighting a methane seep. The BBC, the Discovery Channel and the History Channel have featured her in documentaries.
But the complex science of Arctic methane is only beginning to be understood. In the desolate wilderness of the Bering Land Bridge National Preserve, a sense of urgency is palpable among Walter and three fellow researchers, hunkered down in neon-orange tents.
An occasional helicopter ferries supplies from Nome, the closest town, soaring over scattered herds of caribou. A red fox scampers through the brush. Across a snowfield, bear tracks recede into the distance, a reminder that field science isn't for sissies.
"Can you shoot a gun?" Walter asks a visitor, as she heads out to one of 20 lakes she is surveying. When the answer is noncommittal, she hands over bear spray and instructs: "Don't use it until the bear is right up close, facing you."
Nowhere is the evidence of a heating planet more dramatic than in the polar regions. Over the last 50 years, the Arctic has warmed twice as fast as the rest of the globe. Last summer, for the first time in recorded history, the North Pole could be circumnavigated. Ice sheets on Greenland and West Antarctica are melting rapidly. Polar bears and emperor penguins are threatened with extinction.
Even as glaciers and sea ice have captured the most headlines, growing concern is now focused on the transformation of permafrost, soils that are frozen year-round
Today, 20% of Earth's land surface is locked up in a deep freeze. But scientists predict that air temperature in the Arctic is likely to rise as much as 6 degrees Celsius, or 10.8 degrees Fahrenheit, by the end of the century. That is expected to boost the emission of carbon compounds from soils.
The upper 3 meters -- about 10 feet -- of permafrost stores 1.9 trillion tons of carbon, more than double the amount in the atmosphere today, according to a recent study in the journal Bioscience.
"We are seeing thawing down to 5 meters," says geophysicist Vladimir Romanovsky of the University of Alaska. "A third to a half of permafrost is already within a degree to a degree and a half [Celsius] of thawing."
If only 1% of permafrost carbon were to be released each year, that could double the globe's annual carbon emissions, Romanovsky notes. "We are at a tipping point for positive feedback," he warns, referring to a process in which warming spurs emissions, which in turn generate more heat, in an uncontrollable cycle.
Walter's work is crucial, according to Romanovsky and others, because global warming hinges partly on the ratio of how much carbon is released as CO2 versus how much as methane, a molecule that contains both carbon and hydrogen. Methane, although a far more potent greenhouse gas than carbon dioxide, breaks down more quickly. But when it does, it oxidizes into a carbon dioxide molecule, which can last more than a century in the atmosphere.
Out on the lake, Walter explains: When organic matter (dead plants and animals) rots in the ground, it gives off carbon dioxide. Much of the organic material of thawed permafrost is expected to release carbon dioxide.
But as ice inside permafrost melts, small sinkholes open in the ground and fill with water, joining together to form millions of ponds and lakes. Organic matter slips from eroding shorelines to lake bottoms, where microbes feed on it. Because lake bottoms are oxygen-free, the microbes generate methane in addition to carbon dioxide -- as in the burping La Brea tar pits.
"These lakes are getting bigger -- in some places by a meter a year," Walter says, scooping out slush from the hole she has punched through 6 inches of ice. Into the seep, she inserts a plastic umbrella-like contraption fitted with a bottle to collect gas and a suspended brick to hold it straight.
Before Walter perfected the methane trap, when she was a graduate student in Siberia, she would swim in near-freezing water, dodging leeches and muskrats. Once she caught pneumonia. Another time, her hair caught on fire as she ignited a methane seep.
On the Seward Peninsula trip, she hikes up to 8 miles a day from lake to lake through snowdrifts. Her hip is black and blue from a fall through the ice. "Methane is hard work," she says with a smile.
At each seep, Walter places a small red flag so her colleagues can find the bubbles. Lawrence Plug, a geophysicist from Dalhousie University in Halifax, Canada; Guido Grosse, a German geologist; and Benjamin M. Jones, a U.S. Geological Survey researcher, help shovel off the ice in straight-line paths, take notes on the size of each bubble group, record the location with global positioning system devices, and measure the depth of the lakes.
In the evening, in a cramped cook tent, jars of peanut butter and Nutella sit amid satellite data maps and a textbook on "Applied Linear Statistical Models." Frosted hats and mittens drip from a clothesline. Jones cooks up a batch of hamburger as Walter labels methane bottles with a marker and enters data into her laptop.
Over the next two years, the researchers, funded by the National Science Foundation and NASA, will move between Siberia and Alaska. They will drill permafrost cores, map seeps and analyze data to produce a model of how methane from Arctic lakes might affect Earth's future climate.
"By figuring out how quickly permafrost thawed in the past, we can test our models to predict how fast it could thaw in the next 100 years," says Plug, who will make the complex calculations. "If the temperature warms a couple of degrees Celsius, the lakes could expand at two or three times their current rate."
Elsewhere, scientists cast a wary eye toward clouds of methane bubbles roiling the waters of the Siberian continental shelf. Those emissions, possibly from subsurface permafrost, are even harder to measure than lake emissions.
Meanwhile, researchers are debating the possibility of eventual seeps from methane hydrates -- icy formations beneath the continental shelves and the ocean bottom, and far below land-based permafrost.
Walsh, at the International Arctic Research Center, emphasizes the "huge range of uncertainty" as to how much climate change methane emissions could trigger. "The potential is there for large releases. But there is also a risk of alarmism."
To many Alaskans, it is hardly news that permafrost is thawing: Across the state, houses have been collapsing and trees tipping over. Researchers estimate that repairing affected schools, roads and bridges will cost up to $6 billion over the next two decades.
But the global implications have yet to sink in.
Out on the wild frontier of climate research, far from the legislatures and the diplomatic gatherings where climate policy is debated, Katey Walter and her colleagues focus on what they call "ground truthing."
And beyond that laborious data-gathering, Walter has a mission: to spread the word about what is happening. At the beginning of her field trip, she stops in Nome and leads a group of fifth-graders, many from Alaska Native tribes, out to poke holes in the ice of a nearby lake and light methane flares.
She talks to them about people who live in faraway cities, driving automobiles and working in industries that emit carbon dioxide. And how that causes warming that is felt in the Arctic. And why, even though there are so few people in Alaska, the ice around them is melting.
"That's what we're studying," she explains. "It's all related."
It may be vitamin D's day in the sun
Vitamin supplements have been both heralded and hyped over the years, only to ultimately fall from grace once research proves them to be little more than placebos in our quest for longer life or better health. But at least one substance may have true merit -- vitamin D.
Long considered just a supplement consumed with calcium for bone health, this humble vitamin may have untapped potential in fighting or preventing disease, suggests an explosion of new research. Not only has it shown promise in reducing the risk of, among other things, diabetes, pancreatic cancer, breast cancer and cardiovascular disease, but it also seems to improve infertility, weight control and memory.
Two advocacy groups have sprung up in the United States to promote the substance. Food industry executives are exploring ways to fortify more products. And PubMed, an international database of medical literature, shows that 2,274 studies referencing the vitamin have been published -- just this year.
"Vitamin D is one hot topic," says Connie Weaver, a professor of foods and nutrition at Purdue University in Indiana.
Next week, hope and hype may collide. An Institute of Medicine committee will convene in Washington to discuss whether the recommended daily intake of vitamin D and calcium should be increased. There, researchers overwhelmed by the vitamin's potential will square off against skeptics who say much more study is needed before people are urged to take vitamin D supplements. Getting the newly suggested amounts would be difficult otherwise.
The last time guidelines were issued on the vitamin was in 1997, long before an onslaught of scientific information suggested people are getting too little. Currently, the recommended daily intake is 200 to 600 international units with an upper limit of 2,000 IU.
Some researchers are advocating at least 600 IU a day, with an upper limit of 10,000 IU. Giving impetus to this push are the facts that many people seem to be deficient and that the nutrient appears to play a role in many conditions.
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FOR THE RECORD:
In Saturday's Section A, an article about vitamin D incorrectly referred to the substance in the skin as melatonin. It's melanin.
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Other scientists say it's too soon to urge everyone to take supplements. An influential report released in June by the Agency for Healthcare Research and Quality found little conclusive evidence to support increasing the recommended amounts.
"I think there is a consensus that we might benefit from higher vitamin D levels," says James C. Fleet, a professor of foods and nutrition at Purdue University and a longtime researcher on the vitamin and prostate cancer. "But the committee is going to ask whether there is existing scientific evidence that is strong enough to make a change."
Vitamin D has long been known to be crucial to bone and muscle health by improving calcium absorption in the intestines and the way calcium is regulated in bones.
More recent research shows that receptors for it are found in almost every organ and tissue system in the body, suggesting that deficiencies may affect many types of cell functions.
When exposed to sunlight, the skin makes the vitamin, but not everyone spends the five minutes a day or so outside that is necessary for synthesis -- and many more people today wear sunscreen to prevent skin cancer.
"A large portion of people fall into the at-risk category, and they would benefit from being brought out of that category," Fleet says. "The question is: Is the current requirement enough to keep most people out of the at-risk category?"
A study of 13,000 Americans, published in March in the Archives of Internal Medicine, found that 50% to 75% have suboptimal levels by current standards. A level of 20 nanograms per milliliter of 25-hydroxyvitamin D -- the form most commonly measured in blood -- has traditionally been considered sufficient.
Most people 50 and older aren't meeting the current recommendations, Weaver says.
The vitamin is found in relatively few dietary sources -- some fortified foods, such as milk and some cereals, and naturally only in some fatty fish, such as salmon. Three cups of fortified milk provide only 300 IU.
"The largest source is sunshine, but not everyone can depend on that," Weaver says. "The elderly, dark-skinned people, higher-latitude dwellers all have trouble getting enough from sun." In darker-skinned people, melatonin in the skin blocks absorption of the ultraviolet rays needed to make the vitamin; older people don't appear to synthesize it from the sun as well as younger people.
Some scientists argue that levels of 40 to 60 ng/mL would be far better for disease prevention. That would require daily intake much higher than the current 200 to 600 IU.
The July issue of the Annals of Epidemiology(09)X0007-4, devoted to vitamin D research, links the vitamin to lower risks of cancers of the breast, colon, ovaries and prostate. Animal and lab studies also demonstrate its importance in many of the cellular mechanisms that control cancer, such as cell growth, cell death, inflammation and DNA repair.
Five studies on colorectal cancer and breast cancer, taken together, showed that people with levels higher than 34 to 52 ng/mL had a 50% reduced cancer risk, says Cindy D. Davis, a researcher at the National Cancer Institute's Nutritional Science Research Group.
Such studies are not proof that the vitamin influences disease development, points out Dr. Karen E. Hansen, an assistant professor at the University of Wisconsin who studies bone health. "People with higher vitamin D may just be healthier for other reasons," she says.
But evidence linking higher blood levels to diabetes and cardiovascular disease is also mounting. A study in December in the Journal of the American College of Cardiology found that deficiency may increase the risk of cardiovascular disease. Other studies have tied lower levels to an increased risk of hypertension, diabetes, stroke and congestive heart failure.
Even for bone health, some studies suggest that about 700 to 800 IU a day are needed to prevent fractures in people over 50, Hansen says. She recommends 800 IU a day, with calcium, to her patients.
Meanwhile, studies show that the previous estimation of a toxic dose -- 2,000 IU a day -- is most likely too conservative. Toxic doses can lead to a dangerous level of calcium in the blood, high blood pressure and even kidney failure.
"It's likely they will increase their recommendation for all ages," Hanson said of the Institute of Medicine committee, which will release its report next year.
But not everyone is convinced the advice should be changed. In a report ordered by the federal government to assist the committee, researchers concluded there is a lack of strong evidence to support altering recommendations. The committee is not expected to change calcium recommendations.
"We did not find data that indicate a specific level of vitamin D intake is associated with adverse outcomes or beneficial health outcomes," said Dr. Thomas A. Trikalinos, co-director of the Tufts Evidence-based Practice Center, which prepared the report.
He said the report was meant to inform the committee and did not make recommendations.
"The report sees the totality of the evidence and tries to put everything into perspective," Trikalinos says.
Already, however, the American Society of Clinical Oncology has recommended a higher intake for breast cancer patients who are deficient.
In October, the American Academy of Pediatrics said children should get 400 IU a day, double the current recommendation.
In November, 18 University of California researchers issued a statement saying 2,000 IU is appropriate for most people.
"I think some of the more vocal advocates are pushing the medical community to move forward" before adequate research is completed, Fleet says.
Dozens of more scientifically rigorous studies are in progress that could help resolve the questions about how much people should consume.
"I think they held this [Institute of Medicine] meeting two to four years too early," Fleet says. "They are working without the big wave of vitamin D research that was initiated after people started pushing for it."
Long considered just a supplement consumed with calcium for bone health, this humble vitamin may have untapped potential in fighting or preventing disease, suggests an explosion of new research. Not only has it shown promise in reducing the risk of, among other things, diabetes, pancreatic cancer, breast cancer and cardiovascular disease, but it also seems to improve infertility, weight control and memory.
Two advocacy groups have sprung up in the United States to promote the substance. Food industry executives are exploring ways to fortify more products. And PubMed, an international database of medical literature, shows that 2,274 studies referencing the vitamin have been published -- just this year.
"Vitamin D is one hot topic," says Connie Weaver, a professor of foods and nutrition at Purdue University in Indiana.
Next week, hope and hype may collide. An Institute of Medicine committee will convene in Washington to discuss whether the recommended daily intake of vitamin D and calcium should be increased. There, researchers overwhelmed by the vitamin's potential will square off against skeptics who say much more study is needed before people are urged to take vitamin D supplements. Getting the newly suggested amounts would be difficult otherwise.
The last time guidelines were issued on the vitamin was in 1997, long before an onslaught of scientific information suggested people are getting too little. Currently, the recommended daily intake is 200 to 600 international units with an upper limit of 2,000 IU.
Some researchers are advocating at least 600 IU a day, with an upper limit of 10,000 IU. Giving impetus to this push are the facts that many people seem to be deficient and that the nutrient appears to play a role in many conditions.
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FOR THE RECORD:
In Saturday's Section A, an article about vitamin D incorrectly referred to the substance in the skin as melatonin. It's melanin.
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Other scientists say it's too soon to urge everyone to take supplements. An influential report released in June by the Agency for Healthcare Research and Quality found little conclusive evidence to support increasing the recommended amounts.
"I think there is a consensus that we might benefit from higher vitamin D levels," says James C. Fleet, a professor of foods and nutrition at Purdue University and a longtime researcher on the vitamin and prostate cancer. "But the committee is going to ask whether there is existing scientific evidence that is strong enough to make a change."
Vitamin D has long been known to be crucial to bone and muscle health by improving calcium absorption in the intestines and the way calcium is regulated in bones.
More recent research shows that receptors for it are found in almost every organ and tissue system in the body, suggesting that deficiencies may affect many types of cell functions.
When exposed to sunlight, the skin makes the vitamin, but not everyone spends the five minutes a day or so outside that is necessary for synthesis -- and many more people today wear sunscreen to prevent skin cancer.
"A large portion of people fall into the at-risk category, and they would benefit from being brought out of that category," Fleet says. "The question is: Is the current requirement enough to keep most people out of the at-risk category?"
A study of 13,000 Americans, published in March in the Archives of Internal Medicine, found that 50% to 75% have suboptimal levels by current standards. A level of 20 nanograms per milliliter of 25-hydroxyvitamin D -- the form most commonly measured in blood -- has traditionally been considered sufficient.
Most people 50 and older aren't meeting the current recommendations, Weaver says.
The vitamin is found in relatively few dietary sources -- some fortified foods, such as milk and some cereals, and naturally only in some fatty fish, such as salmon. Three cups of fortified milk provide only 300 IU.
"The largest source is sunshine, but not everyone can depend on that," Weaver says. "The elderly, dark-skinned people, higher-latitude dwellers all have trouble getting enough from sun." In darker-skinned people, melatonin in the skin blocks absorption of the ultraviolet rays needed to make the vitamin; older people don't appear to synthesize it from the sun as well as younger people.
Some scientists argue that levels of 40 to 60 ng/mL would be far better for disease prevention. That would require daily intake much higher than the current 200 to 600 IU.
The July issue of the Annals of Epidemiology(09)X0007-4, devoted to vitamin D research, links the vitamin to lower risks of cancers of the breast, colon, ovaries and prostate. Animal and lab studies also demonstrate its importance in many of the cellular mechanisms that control cancer, such as cell growth, cell death, inflammation and DNA repair.
Five studies on colorectal cancer and breast cancer, taken together, showed that people with levels higher than 34 to 52 ng/mL had a 50% reduced cancer risk, says Cindy D. Davis, a researcher at the National Cancer Institute's Nutritional Science Research Group.
Such studies are not proof that the vitamin influences disease development, points out Dr. Karen E. Hansen, an assistant professor at the University of Wisconsin who studies bone health. "People with higher vitamin D may just be healthier for other reasons," she says.
But evidence linking higher blood levels to diabetes and cardiovascular disease is also mounting. A study in December in the Journal of the American College of Cardiology found that deficiency may increase the risk of cardiovascular disease. Other studies have tied lower levels to an increased risk of hypertension, diabetes, stroke and congestive heart failure.
Even for bone health, some studies suggest that about 700 to 800 IU a day are needed to prevent fractures in people over 50, Hansen says. She recommends 800 IU a day, with calcium, to her patients.
Meanwhile, studies show that the previous estimation of a toxic dose -- 2,000 IU a day -- is most likely too conservative. Toxic doses can lead to a dangerous level of calcium in the blood, high blood pressure and even kidney failure.
"It's likely they will increase their recommendation for all ages," Hanson said of the Institute of Medicine committee, which will release its report next year.
But not everyone is convinced the advice should be changed. In a report ordered by the federal government to assist the committee, researchers concluded there is a lack of strong evidence to support altering recommendations. The committee is not expected to change calcium recommendations.
"We did not find data that indicate a specific level of vitamin D intake is associated with adverse outcomes or beneficial health outcomes," said Dr. Thomas A. Trikalinos, co-director of the Tufts Evidence-based Practice Center, which prepared the report.
He said the report was meant to inform the committee and did not make recommendations.
"The report sees the totality of the evidence and tries to put everything into perspective," Trikalinos says.
Already, however, the American Society of Clinical Oncology has recommended a higher intake for breast cancer patients who are deficient.
In October, the American Academy of Pediatrics said children should get 400 IU a day, double the current recommendation.
In November, 18 University of California researchers issued a statement saying 2,000 IU is appropriate for most people.
"I think some of the more vocal advocates are pushing the medical community to move forward" before adequate research is completed, Fleet says.
Dozens of more scientifically rigorous studies are in progress that could help resolve the questions about how much people should consume.
"I think they held this [Institute of Medicine] meeting two to four years too early," Fleet says. "They are working without the big wave of vitamin D research that was initiated after people started pushing for it."
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