_Atrazine
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Frogs feminized, but atrazine's effects on people uncertain.
Atrazine, one of the most widely used farm pesticides in the United States, has feminized male frogs and other animals in some scientific studies. But research examining potential effects in people is relatively sparse.
A few studies have found possible connections between atrazine and higher rates of some birth defects and poor semen quality in men. Yet scientists say more human research is needed to reach any conclusions. “It pales in comparison to the animal research,” said Dr. Paul Winchester, an Indiana University professor of clinical pediatrics who studies the pesticide.
For more than half a century, U.S. farmers have used large volumes of atrazine to kill weeds, particularly in cornfields. The herbicide has been found in waterways and aquifers that supply drinking water. Syngenta, its manufacturer, says that the chemical is safe for both humans and wildlife at levels found in the environment.
But about a decade ago, researchers at University of California, Berkeley, found that low concentrations – the amount expected near farms – caused male tadpoles to turn into female frogs.
Follow-up studies in the wild found that atrazine either turned male tadpoles into females or “demasculinized” them, causing eggs to grow in their testes and rendering them unable to reproduce, said Tyrone Hayes, a UC Berkeley professor of biology who led the research.
The chemical can disrupt hormones and alter male reproductive tissues when an animal is exposed during development. Other impacts include a reduction in size at birth, according to 2005 and 2008 studies of amphibians and fish by University of Texas researchers.
And it’s not just frogs that might be at risk of being feminized – recent research has found that atrazine has similar hormonal effects on salmon, caimans and lab rats.
In addition, “it’s been shown to cause erratic behavior, like weird swimming patterns,” Hayes said. “Fish and frogs start swimming improperly, which has consequences – they can’t escape predators, they can’t find food.”
“It [atrazine] has been shown to cause erratic behavior, like weird swimming patterns. Fish and frogs start swimming improperly, which has consequences – they can’t escape predators, they can’t find food.” -Tyrone Hayes, UC Berkeley Syngenta disputes all these findings. The Swiss-based company particularly took issue with Hayes’ research, and cited follow-up studies that could not replicate his work and reported no feminizing effects on frogs. Peer-reviewed and published, the industry studies were conducted at two labs, and were funded by Syngenta after the U.S. Environmental Protection Agency asked the company in 2003 to perform more frog tests.
Hayes in 2004 wrote a paper slamming Syngenta's studies, saying there were errors, such as high mortality of frogs and inappropriate measurements of hormone levels. He said due to those factors, their research cannot be compared with his. "All of the studies that say [atrazine] doesn’t have any effect come from industry. We're all finding reproductive effects, except those who are getting paid [by Syngenta],” he said.
The field studies of frogs that couldn’t replicate Hayes’ findings used different, less-accurate methods, said Krista McCoy, a professor of biology at East Carolina University and co-author of a 2010 analysis of atrazine and wildlife research.
McCoy said the studies that didn’t find a link assumed that some ponds were clean and could be used as a reference site. When the researchers found similar abnormalities in frogs from the so-called “clean” site and polluted site, they reported no link to atrazine.
But “there’s no such thing as a clean control site where there’s no manmade chemicals,” McCoy said. “If you collect samples from a pond in an agricultural area and then go across the street to someone’s yard, well, the animals [in the non-agricultural pond] are probably exposed to the same chemicals due to runoff.”
McCoy’s analysis of previous research concluded that atrazine consistently affected reproductive development of male frogs in studies. But it’s unclear whether any animal populations are dropping due to possible effects from the herbicide.
Jason Rohr, a biology professor at the University of South Florida and co-author of that analysis, has some concerns about all of the atrazine research. “There are problems with some of Tyrone’s [Hayes] work, some of it is fantastic,” Rohr said. He wondered whether any variables were introduced in the Syngenta-funded studies that may skew the results.
Europe banned atrazine in 2003 because of its widespread discovery in water supplies. But the EPA concluded that water containing atrazine at 3 parts per billion is safe to drink. The agency, however, has initiated another review of data collected since 2007 on both human and wildlife health.In a 2007 review of the chemical, the EPA agreed with Syngenta and renewed the registration of atrazine, concluding that it was not harming frogs and other wildlife at levels found in the environment. “Based on the negative results of these studies, the Agency concludes that it is reasonable to reject the hypothesis…that atrazine exposure can affect amphibian gonadal development,” the EPA said in its review.
Under federal law, “a pesticide must be found not to cause unreasonable risks to people or the environment” in order for the EPA to allow continued use. But the law also allows the EPA to take into “account the economic, social, and environmental costs and benefits of the use of the pesticide” when assessing “unreasonable risks.” Pesticides are reviewed every 15 years.
Europe banned atrazine in 2003 because of its widespread discovery in water supplies. But the EPA concluded that water containing atrazine at 3 parts per billion is safe to drink. The agency, however, has initiated another review of data collected since 2007 on both human and wildlife health.
One recent study offers clues to the mechanisms through which atrazine can harm animals and possibly humans.
Purdue University researchers found that zebrafish embryos exposed to atrazine at environmental levels showed changes in their genes. “The genes that were altered were associated with neuroendocrine, reproductive function in the fish,” said Jennifer Freeman, a toxicology professor at Purdue University who was the study’s senior author.
While the study didn’t examine whether these gene changes led to health problems, Freeman said it’s plausible that they could be behind some developmental and reproductive effects seen in wildlife. She said these genes work in similar ways in fish and humans.
The strongest evidence of a possible human effect is a study comparing men in a rural area of Missouri to men in three urban areas. The Missouri men with higher atrazine exposures were more likely to have poor semen quality, perhaps due to the chemical’s ability to alter sex hormones, according to the study published a decade ago. Similar effects were reported on the sperm of lab animals.
Another large study, conducted in France, showed babies exposed in the womb to atrazine are born weighing slightly less, by an average of five ounces.
The herbicide also has been linked to changes in breast tissue and birth defects in exposed lab rats, which are used to determine if the chemicals are a danger to humans.
The strongest evidence of a possible human effect is a study comparing men in a rural area of Missouri to men in three urban areas. The Missouri men with higher atrazine exposures were more likely to have poor semen quality.Toxicologist Suzanne Fenton, a leading atrazine researcher at the National Institute of Environmental Health Sciences, said when mother rats are exposed to high doses of atrazine, their pups have developmental delays in mammary glands, which may increase susceptibility to breast cancer.
But the International Agency for Research on Cancer has concluded that there is “inadequate evidence” to say that atrazine causes cancer in humans, and the EPA reported in 2006 that it is “not likely to be carcinogenic to humans.”
“All of the human studies I know of have some issues,” Fenton said. “The hard part about atrazine work is that it has a really short half-life in humans/animals. Hard to measure accurately.”
Similar to rat studies, atrazine has been linked to some birth defects in humans. A study published this year that reviewed birth defect records in Texas found “modest, but consistent, associations” between boys’ genital defects and mothers who live near areas with atrazine. A 2007 study in Indiana found an increased rate of abdominal defects in children born in areas with higher atrazine levels in surface waters. Also, U.S. babies conceived in April through August, when farm chemicals including atrazine were at their highest amounts in water, had more birth defects, according to research by Winchester and colleagues.
However, all three of these birth defect studies had to estimate atrazine exposure, making it questionable whether the health impact was from the chemical and not from some other factor. For example, the scientists don’t know how much atrazine the mothers were actually exposed to; they just know they lived in areas where it was found in streams. Also, the study in France that did measure atrazine in mothers found no increase in birth defects in their children.
Winchester said his research linking agricultural months to birth defects “certainly doesn’t prove that atrazine causes birth defects…but we simply can’t rule it out as a cause.”
“We’re not looking for a fight [with Syngenta],” he said. “We’re just looking for answers.”
Source : Environmental Health News
Link to Full Article
Special Report: Syngenta's campaign to protect atrazine, discredit critics.
To protect profits threatened by a lawsuit over its controversial herbicide atrazine, Syngenta Crop Protection launched an aggressive multi-million dollar campaign that included hiring a detective agency to investigate scientists on a federal advisory panel, looking into the personal life of a judge and commissioning a psychological profile of a leading scientist critical of atrazine. The Switzerland-based pesticide manufacturer also routinely paid “third-party allies” to appear to be independent supporters, and kept a list of 130 people and groups it could recruit as experts without disclosing ties to the company. Recently unsealed court documents reveal a corporate strategy to discredit critics and to strip plaintiffs from the class-action case. The company specifically targeted one of atrazine’s fiercest and most outspoken critics, UC-Berkeley's Tyrone Hayes, whose research suggests that atrazine feminizes male frogs. The campaign is spelled out in hundreds of pages of memos, invoices and other documents from Illinois’ Madison County Circuit Court, that were initially sealed as part of a 2004 lawsuit filed by Holiday Shores Sanitary District. The new documents, along with an earlier tranche, open a window on the company’s strategy to defeat a lawsuit that could have effectively ended sales of atrazine in the United States.
Source : Environmental Health News
Link to Full Special Report
Exposure to atrazine, a common weedkiller, during pregnancy may raise the risk of a rare nasal blockage birth defect, researchers found.
Women exposed to high levels of the herbicide at home were almost twice as likely to have children with choanal atresia or stenosis, Philip J. Lupo, PhD, of the University of Texas School of Public Health, and colleagues found in an observational study.
The risk appeared to be dose-dependent, the group reported online in the Journal of Pediatrics.
Atrazine is the most commonly used herbicide in the U.S., although the CDC's Agency for Toxic Substances and Disease Registry notes most exposure is around farms where it has been sprayed, rather than through household use.
The agency recommends staying away from fields that have recently been sprayed, not swimming in or drinking from contaminated water, and not letting children play in dirt near where atrazine may have been discarded.
The chemical has been shown to cause other birth defects and is linked to gastroschisis, spina bifida, cleft lip, congenital heart defects, limb reduction defects, and urogenital defects. It is also a known endocrine disruptor.
Since choanal atresia is suspected to arise from maternal endocrine problems, the researchers examined the population-based Texas Birth Defects Registry for links to maternal exposure to atrazine at home during pregnancy.
Atrazine exposure was estimated by the U.S. Geological Survey, which calculates exposure based on the county's annual crop acreage and type likely to have been sprayed with the chemical.
Active case surveillance from 1999 through 2008 turned up 280 cases of choanal atresia or stenosis without additional major malformations or genetic syndromes.
The potentially life-threatening defect blocks off the back of the nasal passage during development and often requires multiple surgeries to restore normal breathing.
When compared with a random 10:1 sample of controls without major malformations delivered during the study period, children whose mothers had the highest estimated atrazine exposure at home were 1.65-fold more likely to be born with the birth defect than those with low exposure levels (95% confidence interval 1.10 to 2.48).
The association actually strengthened to an odds ratio of 1.79 with adjustment for season of conception, the child's sex, birth year, and maternal factors like race or ethnicity, education, age, and smoking status (95% CI 1.17 to 2.74).
Increasing exposure correlated with higher choanal atresia or stenosis risk both in the adjusted and unadjusted analyses (adjusted P=0.002).
Risk of the birth defect rose 49% for each 100 pounds of atrazine used per square mile in the county (95% CI 1.09 to 2.04).
These results have to be interpreted cautiously because of the county-level estimates used due to a lack of any large-scale population-based measures of atrazine exposure in individuals, the researchers cautioned.
"However, living in areas with high levels of atrazine application (e.g., proximity to agricultural fields) appears to correlate with personal exposure," they noted. "For instance, families living in farm households have higher levels of urine atrazine metabolites compared to families living in nonfarm households."
The group also cautioned that the study couldn't rule out confounding by unmeasured variables.
"Thus, the present study is an important first step in determining what associations may be present," they wrote. "Future research is needed to confirm our findings, using other exposure assessment methodologies, including biomarkers of exposure."
Source : MedPage Today
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Herbicide atrazine spurs reproductive problems in many creatures
An international team of researchers has reviewed the evidence linking exposure to atrazine -- an herbicide widely used in the U.S. and more than 60 other nations -- to reproductive problems in animals. The team found consistent patterns of reproductive dysfunction in amphibians, fish, reptiles and mammals exposed to the chemical. Atrazine is the second-most widely used herbicide in the U.S. More than 75 million pounds of it are applied to corn and other crops, and it is the most commonly detected pesticide contaminant of groundwater, surface water and rain in the U.S.
The new review, compiled by 22 scientists studying atrazine in North and South America, Europe and Japan, appears in the Journal of Steroid Biochemistry and Molecular Biology.
The researchers looked at studies linking atrazine exposure to abnormal androgen (male hormone) levels in fish, amphibians, reptiles and mammals and studies that found a common association between exposure to the herbicide and the "feminization" of male gonads in many animals.
The most robust findings are in amphibians, said University of Illinois comparative biosciences professor Val Beasley, a co-author of the review. At least 10 studies found that exposure to atrazine feminizes male frogs, sometimes to the point of sex reversal, he said.
Beasley's lab was one of the first to find that male frogs exposed to atrazine in the wild were more likely to have both male and female gonadal tissue than frogs living in an atrazine-free environment. And in a 2010 study, Tyrone Hayes, a professor of integrative biology at the University of California at Berkeley and lead author of the review, reported in the Proceedings of the National Academy of Sciences that atrazine exposure in frogs was associated with "genetic males becoming females and functioning as females," Beasley said.
"And this is not at extremely high concentrations," he said. "These are at concentrations that are found in the environment."
The new review describes the disruptions of hormone function and sexual development reported in studies of mammals, frogs, fish, reptiles and human cells exposed to the herbicide. The studies found that atrazine exposure can change the expression of genes involved in hormone signaling, interfere with metamorphosis, inhibit key enzymes that control estrogen and androgen production, skew the sex ratio of wild and laboratory animals (toward female) and otherwise disrupt the normal reproductive development and functioning of males and females.
"One of the things that became clear in writing this paper is that atrazine works through a number of different mechanisms," Hayes said. "It's been shown that it increases production of (the stress hormone) cortisol. It's been shown that it inhibits key enzymes in steroid hormone production while increasing others. It's been shown that it somehow prevents androgen from binding to its receptor."
The review also consolidates the evidence that atrazine undermines immune function in a variety of animals, in part by increasing cortisol.
"Cortisol is a nonspecific response to chronic stress," Beasley said. "But guess what? Wildlife in many of today's habitats are stressed a great deal of the time. They're stressed because they're crowded into little remnant habitats. They're stressed because there's not enough oxygen in the water because there are not enough plants in the water (another consequence of herbicide use). They're stressed because of other contaminants in the water. And the long-term release of cortisol causes them to be immuno-suppressed."
There also are studies that show no effects -- or different effects -- in animals exposed to atrazine, Beasley said. "But the studies are not all the same. There are different species, different times of exposure, different stages of development and different strains within a species." All in all, he said, the evidence that atrazine harms animals, particularly amphibians and other creatures that encounter it in the water, is compelling.
"I hope this will stimulate policymakers to look at the totality of the data and ask very broad questions," Hayes said. "Do we want this stuff in our environment? Do we want -- knowing what we know -- our children to drink this stuff? I would think the answer would be no."
Source : e Science News
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Atrazine in Water tied to menstrual irregularities, low hormones
Women who drink water contaminated with low levels of the weed-killer atrazine may be more likely to have irregular menstrual cycles and low estrogen levels, scientists concluded in a new study. The most widely used herbicide in the United States, atrazine is frequently detected in surface and ground water, particularly in agricultural areas of the Midwest. The newest research, which compared women in Illinois farm towns to women in Vermont, adds to the growing scientific evidence linking atrazine to altered hormones.
The manufacturer of atrazine says some unknown factor – not atrazine – might have caused the menstrual irregularities.
“Many things can cause changes to a woman’s menstrual cycle – stress, exercise, diet,” said Tim Pastoor, principle scientist for Syngenta, the Switzerland-based company that makes atrazine.
Pastoor noted that the company’s mice studies have not found reproductive effects, even at atrazine levels far greater than those found in the drinking water in the new study.
The researchers did not test the water for other contaminants.
“It is possible that the difference we found is due to pesticide exposure in general or another, unmeasured chemical in the drinking water,” said Cragin, who now is an epidemiologist at the Vermont Department of Public Health.
Cragin and her team, which included researchers from Colorado State University, Emory University and the Centers for Disease Control and Prevention, collected questionnaires from 102 premenopausal women in the Illinois farm towns of Mount Olive and Gillespie, and in the Vermont towns of Waterbury and Fair Haven, where atrazine is not used. The authors said they considered lifestyle factors, such as physical activity, weight and foods, and found no significant differences between the two groups of women.
The findings, which were published in the journal Environmental Research earlier this month, were based on municipal tap water tested between July and September of 2005.
Cragin was surprised to see a significant effect in the women whose water contained atrazine levels far below the EPA’s standard of 3 parts per billion.
The research team was surprised to see a significant effect in the women whose water contained atrazine levels far below the EPA’s standard of 3 parts per billion.In Illinois water, the average concentration of atrazine was 0.7 parts per billion, several times lower than the averages recorded in previous and subsequent summers. Cragin said drought conditions in 2005 would have slowed runoff from farm fields.
The researchers did not examine whether the menstrual and hormonal changes reduced the women’s ability to become pregnant. However, estrogen levels and menstrual cycle characteristics are known to affect fertility.
“These types of changes to hormone concentration and ovarian function could potentially lead to problems with fertility,” said Emily Barrett, a reproductive health scientist at the University of Rochester in New York.
Hormonal changes also have been associated with greater risk of certain diseases such as osteoporosis, diabetes, heart disease and some cancers.
Though scientists are not sure how atrazine would disrupt hormone levels, some studies suggest that the chemical may block the production of estrogen in the body.
Hormonal changes have been associated with greater risk of certain diseases such as osteoporosis, diabetes, heart disease and some cancers.The small number of women involved in the study could increase the possibility that the differences between the two communities are due to chance. However, “to find a profoundly higher incidence of reproductive irregularities in such a small group of people suggests that something is definitely going on here,” said Laura Vandenberg, a reproductive scientist at Tufts University.
First registered as an herbicide in 1958, atrazine is used primarily to eliminate weeds on land where crops including corn and sorghum grow, but it is sometimes used on lawns and golf courses too.
In 2003, the EPA reevaluated the safety of atrazine and determined that the current safety standard of 3 parts per billion is sufficient to protect against hormonal effects of atrazine.
At the time, the EPA mandated Syngenta to begin monitoring roughly 100 community water systems nationwide for levels of the chemical in drinking water. Environmental groups criticized the decision because they said it allowed the chemical company to oversee itself.
Since 2003, more than 150 new studies raising concerns about the potential health effects of atrazine have been published. The European Union has since banned it due to safety concerns.
Women who drink water contaminated with low levels of the weed-killer atrazine may be more likely to have irregular menstrual cycles and low estrogen levels, scientists concluded in a new study.
The most widely used herbicide in the United States, atrazine is frequently detected in surface and ground water, particularly in agricultural areas of the Midwest. Approximately 75 percent of all U.S. cornfields are treated with atrazine each year.
The newest research, which compared women in Illinois to women in Vermont, adds to the growing scientific evidence linking atrazine to altered hormones.
The women from Illinois farm towns were nearly five times more likely to report irregular periods than the Vermont women, and more than six times as likely to go more than six weeks between periods. In addition, the Illinois women had significantly lower levels of estrogen during an important part of the menstrual cycle.
Tap water in the Illinois communities had double the concentration of atrazine in the Vermont communities’ water. Nevertheless, the water in both states was far below the federal drinking water standard currently enforced by the U.S. Environmental Protection Agency.
Approximately 75 percent of all U.S. cornfields are treated with atrazine each year. It also is sometimes used on lawns and golf courses to kill weeds.The amount of water consumed also seemed to make a difference: Women who said they drank more than two cups of Illinois tap water daily reported an even greater occurrence of irregular periods.
In recent years, some tests on lab animals have linked the herbicide to fertility issues, including altered hormone levels, delayed puberty and pregnancy loss.
Co-author Lori Cragin, an epidemiologist with Colorado State University at the time of the study, said the new findings fit with the results of the animal studies, as well as with some limited research that reported human effects.
In 2009, a study tied atrazine in drinking water to low birth weight in Indiana newborns. And in a study of more than 3,000 women enrolled in the Agricultural Health Study, those who described using atrazine and other pesticides had an increased risk of missed periods and bleeding between periods. The Agricultural Health Study is a nationwide project sponsored by the National Institutes of Health.
Studies in frogs suggest that atrazine, even at low levels, may affect development of the male reproductive system, decreasing fertility and in some cases leading to hermaphroditic frogs.
“In frogs, atrazine disrupts the balance between what it means to develop and function as a male or a female,” said Tyrone Hayes, a scientist from the University of California, Berkeley who studies the reproductive effects of pesticides in frogs.
In 2009, the EPA ordered another review in light of new studies. The agency is currently awaiting the results of an evaluation by a scientific advisory panel.
In the meantime, use of the herbicide continues to rise. In the first half of 2011 alone, Syngenta reported double-digit growth in sales, with atrazine as a high performer.
Some environmental groups and scientists are frustrated with the pace of the regulatory process when it comes to evaluating chemical safety.
“We can’t continue to allow the use of this chemical when we are seeing adverse effects on animals and people,” said Vandenberg.
Source : Environmental Health News
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Frogs feminized, but atrazine's effects on people uncertain.
Atrazine, one of the most widely used farm pesticides in the United States, has feminized male frogs and other animals in some scientific studies. But research examining potential effects in people is relatively sparse.
A few studies have found possible connections between atrazine and higher rates of some birth defects and poor semen quality in men. Yet scientists say more human research is needed to reach any conclusions. “It pales in comparison to the animal research,” said Dr. Paul Winchester, an Indiana University professor of clinical pediatrics who studies the pesticide.
For more than half a century, U.S. farmers have used large volumes of atrazine to kill weeds, particularly in cornfields. The herbicide has been found in waterways and aquifers that supply drinking water. Syngenta, its manufacturer, says that the chemical is safe for both humans and wildlife at levels found in the environment.
But about a decade ago, researchers at University of California, Berkeley, found that low concentrations – the amount expected near farms – caused male tadpoles to turn into female frogs.
Follow-up studies in the wild found that atrazine either turned male tadpoles into females or “demasculinized” them, causing eggs to grow in their testes and rendering them unable to reproduce, said Tyrone Hayes, a UC Berkeley professor of biology who led the research.
The chemical can disrupt hormones and alter male reproductive tissues when an animal is exposed during development. Other impacts include a reduction in size at birth, according to 2005 and 2008 studies of amphibians and fish by University of Texas researchers.
And it’s not just frogs that might be at risk of being feminized – recent research has found that atrazine has similar hormonal effects on salmon, caimans and lab rats.
In addition, “it’s been shown to cause erratic behavior, like weird swimming patterns,” Hayes said. “Fish and frogs start swimming improperly, which has consequences – they can’t escape predators, they can’t find food.”
“It [atrazine] has been shown to cause erratic behavior, like weird swimming patterns. Fish and frogs start swimming improperly, which has consequences – they can’t escape predators, they can’t find food.” -Tyrone Hayes, UC Berkeley Syngenta disputes all these findings. The Swiss-based company particularly took issue with Hayes’ research, and cited follow-up studies that could not replicate his work and reported no feminizing effects on frogs. Peer-reviewed and published, the industry studies were conducted at two labs, and were funded by Syngenta after the U.S. Environmental Protection Agency asked the company in 2003 to perform more frog tests.
Hayes in 2004 wrote a paper slamming Syngenta's studies, saying there were errors, such as high mortality of frogs and inappropriate measurements of hormone levels. He said due to those factors, their research cannot be compared with his. "All of the studies that say [atrazine] doesn’t have any effect come from industry. We're all finding reproductive effects, except those who are getting paid [by Syngenta],” he said.
The field studies of frogs that couldn’t replicate Hayes’ findings used different, less-accurate methods, said Krista McCoy, a professor of biology at East Carolina University and co-author of a 2010 analysis of atrazine and wildlife research.
McCoy said the studies that didn’t find a link assumed that some ponds were clean and could be used as a reference site. When the researchers found similar abnormalities in frogs from the so-called “clean” site and polluted site, they reported no link to atrazine.
But “there’s no such thing as a clean control site where there’s no manmade chemicals,” McCoy said. “If you collect samples from a pond in an agricultural area and then go across the street to someone’s yard, well, the animals [in the non-agricultural pond] are probably exposed to the same chemicals due to runoff.”
McCoy’s analysis of previous research concluded that atrazine consistently affected reproductive development of male frogs in studies. But it’s unclear whether any animal populations are dropping due to possible effects from the herbicide.
Jason Rohr, a biology professor at the University of South Florida and co-author of that analysis, has some concerns about all of the atrazine research. “There are problems with some of Tyrone’s [Hayes] work, some of it is fantastic,” Rohr said. He wondered whether any variables were introduced in the Syngenta-funded studies that may skew the results.
Europe banned atrazine in 2003 because of its widespread discovery in water supplies. But the EPA concluded that water containing atrazine at 3 parts per billion is safe to drink. The agency, however, has initiated another review of data collected since 2007 on both human and wildlife health.In a 2007 review of the chemical, the EPA agreed with Syngenta and renewed the registration of atrazine, concluding that it was not harming frogs and other wildlife at levels found in the environment. “Based on the negative results of these studies, the Agency concludes that it is reasonable to reject the hypothesis…that atrazine exposure can affect amphibian gonadal development,” the EPA said in its review.
Under federal law, “a pesticide must be found not to cause unreasonable risks to people or the environment” in order for the EPA to allow continued use. But the law also allows the EPA to take into “account the economic, social, and environmental costs and benefits of the use of the pesticide” when assessing “unreasonable risks.” Pesticides are reviewed every 15 years.
Europe banned atrazine in 2003 because of its widespread discovery in water supplies. But the EPA concluded that water containing atrazine at 3 parts per billion is safe to drink. The agency, however, has initiated another review of data collected since 2007 on both human and wildlife health.
One recent study offers clues to the mechanisms through which atrazine can harm animals and possibly humans.
Purdue University researchers found that zebrafish embryos exposed to atrazine at environmental levels showed changes in their genes. “The genes that were altered were associated with neuroendocrine, reproductive function in the fish,” said Jennifer Freeman, a toxicology professor at Purdue University who was the study’s senior author.
While the study didn’t examine whether these gene changes led to health problems, Freeman said it’s plausible that they could be behind some developmental and reproductive effects seen in wildlife. She said these genes work in similar ways in fish and humans.
The strongest evidence of a possible human effect is a study comparing men in a rural area of Missouri to men in three urban areas. The Missouri men with higher atrazine exposures were more likely to have poor semen quality, perhaps due to the chemical’s ability to alter sex hormones, according to the study published a decade ago. Similar effects were reported on the sperm of lab animals.
Another large study, conducted in France, showed babies exposed in the womb to atrazine are born weighing slightly less, by an average of five ounces.
The herbicide also has been linked to changes in breast tissue and birth defects in exposed lab rats, which are used to determine if the chemicals are a danger to humans.
The strongest evidence of a possible human effect is a study comparing men in a rural area of Missouri to men in three urban areas. The Missouri men with higher atrazine exposures were more likely to have poor semen quality.Toxicologist Suzanne Fenton, a leading atrazine researcher at the National Institute of Environmental Health Sciences, said when mother rats are exposed to high doses of atrazine, their pups have developmental delays in mammary glands, which may increase susceptibility to breast cancer.
But the International Agency for Research on Cancer has concluded that there is “inadequate evidence” to say that atrazine causes cancer in humans, and the EPA reported in 2006 that it is “not likely to be carcinogenic to humans.”
“All of the human studies I know of have some issues,” Fenton said. “The hard part about atrazine work is that it has a really short half-life in humans/animals. Hard to measure accurately.”
Similar to rat studies, atrazine has been linked to some birth defects in humans. A study published this year that reviewed birth defect records in Texas found “modest, but consistent, associations” between boys’ genital defects and mothers who live near areas with atrazine. A 2007 study in Indiana found an increased rate of abdominal defects in children born in areas with higher atrazine levels in surface waters. Also, U.S. babies conceived in April through August, when farm chemicals including atrazine were at their highest amounts in water, had more birth defects, according to research by Winchester and colleagues.
However, all three of these birth defect studies had to estimate atrazine exposure, making it questionable whether the health impact was from the chemical and not from some other factor. For example, the scientists don’t know how much atrazine the mothers were actually exposed to; they just know they lived in areas where it was found in streams. Also, the study in France that did measure atrazine in mothers found no increase in birth defects in their children.
Winchester said his research linking agricultural months to birth defects “certainly doesn’t prove that atrazine causes birth defects…but we simply can’t rule it out as a cause.”
“We’re not looking for a fight [with Syngenta],” he said. “We’re just looking for answers.”
Source : Environmental Health News
Link to Full Article
Special Report: Syngenta's campaign to protect atrazine, discredit critics.
To protect profits threatened by a lawsuit over its controversial herbicide atrazine, Syngenta Crop Protection launched an aggressive multi-million dollar campaign that included hiring a detective agency to investigate scientists on a federal advisory panel, looking into the personal life of a judge and commissioning a psychological profile of a leading scientist critical of atrazine. The Switzerland-based pesticide manufacturer also routinely paid “third-party allies” to appear to be independent supporters, and kept a list of 130 people and groups it could recruit as experts without disclosing ties to the company. Recently unsealed court documents reveal a corporate strategy to discredit critics and to strip plaintiffs from the class-action case. The company specifically targeted one of atrazine’s fiercest and most outspoken critics, UC-Berkeley's Tyrone Hayes, whose research suggests that atrazine feminizes male frogs. The campaign is spelled out in hundreds of pages of memos, invoices and other documents from Illinois’ Madison County Circuit Court, that were initially sealed as part of a 2004 lawsuit filed by Holiday Shores Sanitary District. The new documents, along with an earlier tranche, open a window on the company’s strategy to defeat a lawsuit that could have effectively ended sales of atrazine in the United States.
Source : Environmental Health News
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Exposure to atrazine, a common weedkiller, during pregnancy may raise the risk of a rare nasal blockage birth defect, researchers found.
Women exposed to high levels of the herbicide at home were almost twice as likely to have children with choanal atresia or stenosis, Philip J. Lupo, PhD, of the University of Texas School of Public Health, and colleagues found in an observational study.
The risk appeared to be dose-dependent, the group reported online in the Journal of Pediatrics.
Atrazine is the most commonly used herbicide in the U.S., although the CDC's Agency for Toxic Substances and Disease Registry notes most exposure is around farms where it has been sprayed, rather than through household use.
The agency recommends staying away from fields that have recently been sprayed, not swimming in or drinking from contaminated water, and not letting children play in dirt near where atrazine may have been discarded.
The chemical has been shown to cause other birth defects and is linked to gastroschisis, spina bifida, cleft lip, congenital heart defects, limb reduction defects, and urogenital defects. It is also a known endocrine disruptor.
Since choanal atresia is suspected to arise from maternal endocrine problems, the researchers examined the population-based Texas Birth Defects Registry for links to maternal exposure to atrazine at home during pregnancy.
Atrazine exposure was estimated by the U.S. Geological Survey, which calculates exposure based on the county's annual crop acreage and type likely to have been sprayed with the chemical.
Active case surveillance from 1999 through 2008 turned up 280 cases of choanal atresia or stenosis without additional major malformations or genetic syndromes.
The potentially life-threatening defect blocks off the back of the nasal passage during development and often requires multiple surgeries to restore normal breathing.
When compared with a random 10:1 sample of controls without major malformations delivered during the study period, children whose mothers had the highest estimated atrazine exposure at home were 1.65-fold more likely to be born with the birth defect than those with low exposure levels (95% confidence interval 1.10 to 2.48).
The association actually strengthened to an odds ratio of 1.79 with adjustment for season of conception, the child's sex, birth year, and maternal factors like race or ethnicity, education, age, and smoking status (95% CI 1.17 to 2.74).
Increasing exposure correlated with higher choanal atresia or stenosis risk both in the adjusted and unadjusted analyses (adjusted P=0.002).
Risk of the birth defect rose 49% for each 100 pounds of atrazine used per square mile in the county (95% CI 1.09 to 2.04).
These results have to be interpreted cautiously because of the county-level estimates used due to a lack of any large-scale population-based measures of atrazine exposure in individuals, the researchers cautioned.
"However, living in areas with high levels of atrazine application (e.g., proximity to agricultural fields) appears to correlate with personal exposure," they noted. "For instance, families living in farm households have higher levels of urine atrazine metabolites compared to families living in nonfarm households."
The group also cautioned that the study couldn't rule out confounding by unmeasured variables.
"Thus, the present study is an important first step in determining what associations may be present," they wrote. "Future research is needed to confirm our findings, using other exposure assessment methodologies, including biomarkers of exposure."
Source : MedPage Today
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Herbicide atrazine spurs reproductive problems in many creatures
An international team of researchers has reviewed the evidence linking exposure to atrazine -- an herbicide widely used in the U.S. and more than 60 other nations -- to reproductive problems in animals. The team found consistent patterns of reproductive dysfunction in amphibians, fish, reptiles and mammals exposed to the chemical. Atrazine is the second-most widely used herbicide in the U.S. More than 75 million pounds of it are applied to corn and other crops, and it is the most commonly detected pesticide contaminant of groundwater, surface water and rain in the U.S.
The new review, compiled by 22 scientists studying atrazine in North and South America, Europe and Japan, appears in the Journal of Steroid Biochemistry and Molecular Biology.
The researchers looked at studies linking atrazine exposure to abnormal androgen (male hormone) levels in fish, amphibians, reptiles and mammals and studies that found a common association between exposure to the herbicide and the "feminization" of male gonads in many animals.
The most robust findings are in amphibians, said University of Illinois comparative biosciences professor Val Beasley, a co-author of the review. At least 10 studies found that exposure to atrazine feminizes male frogs, sometimes to the point of sex reversal, he said.
Beasley's lab was one of the first to find that male frogs exposed to atrazine in the wild were more likely to have both male and female gonadal tissue than frogs living in an atrazine-free environment. And in a 2010 study, Tyrone Hayes, a professor of integrative biology at the University of California at Berkeley and lead author of the review, reported in the Proceedings of the National Academy of Sciences that atrazine exposure in frogs was associated with "genetic males becoming females and functioning as females," Beasley said.
"And this is not at extremely high concentrations," he said. "These are at concentrations that are found in the environment."
The new review describes the disruptions of hormone function and sexual development reported in studies of mammals, frogs, fish, reptiles and human cells exposed to the herbicide. The studies found that atrazine exposure can change the expression of genes involved in hormone signaling, interfere with metamorphosis, inhibit key enzymes that control estrogen and androgen production, skew the sex ratio of wild and laboratory animals (toward female) and otherwise disrupt the normal reproductive development and functioning of males and females.
"One of the things that became clear in writing this paper is that atrazine works through a number of different mechanisms," Hayes said. "It's been shown that it increases production of (the stress hormone) cortisol. It's been shown that it inhibits key enzymes in steroid hormone production while increasing others. It's been shown that it somehow prevents androgen from binding to its receptor."
The review also consolidates the evidence that atrazine undermines immune function in a variety of animals, in part by increasing cortisol.
"Cortisol is a nonspecific response to chronic stress," Beasley said. "But guess what? Wildlife in many of today's habitats are stressed a great deal of the time. They're stressed because they're crowded into little remnant habitats. They're stressed because there's not enough oxygen in the water because there are not enough plants in the water (another consequence of herbicide use). They're stressed because of other contaminants in the water. And the long-term release of cortisol causes them to be immuno-suppressed."
There also are studies that show no effects -- or different effects -- in animals exposed to atrazine, Beasley said. "But the studies are not all the same. There are different species, different times of exposure, different stages of development and different strains within a species." All in all, he said, the evidence that atrazine harms animals, particularly amphibians and other creatures that encounter it in the water, is compelling.
"I hope this will stimulate policymakers to look at the totality of the data and ask very broad questions," Hayes said. "Do we want this stuff in our environment? Do we want -- knowing what we know -- our children to drink this stuff? I would think the answer would be no."
Source : e Science News
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Atrazine in Water tied to menstrual irregularities, low hormones
Women who drink water contaminated with low levels of the weed-killer atrazine may be more likely to have irregular menstrual cycles and low estrogen levels, scientists concluded in a new study. The most widely used herbicide in the United States, atrazine is frequently detected in surface and ground water, particularly in agricultural areas of the Midwest. The newest research, which compared women in Illinois farm towns to women in Vermont, adds to the growing scientific evidence linking atrazine to altered hormones.
The manufacturer of atrazine says some unknown factor – not atrazine – might have caused the menstrual irregularities.
“Many things can cause changes to a woman’s menstrual cycle – stress, exercise, diet,” said Tim Pastoor, principle scientist for Syngenta, the Switzerland-based company that makes atrazine.
Pastoor noted that the company’s mice studies have not found reproductive effects, even at atrazine levels far greater than those found in the drinking water in the new study.
The researchers did not test the water for other contaminants.
“It is possible that the difference we found is due to pesticide exposure in general or another, unmeasured chemical in the drinking water,” said Cragin, who now is an epidemiologist at the Vermont Department of Public Health.
Cragin and her team, which included researchers from Colorado State University, Emory University and the Centers for Disease Control and Prevention, collected questionnaires from 102 premenopausal women in the Illinois farm towns of Mount Olive and Gillespie, and in the Vermont towns of Waterbury and Fair Haven, where atrazine is not used. The authors said they considered lifestyle factors, such as physical activity, weight and foods, and found no significant differences between the two groups of women.
The findings, which were published in the journal Environmental Research earlier this month, were based on municipal tap water tested between July and September of 2005.
Cragin was surprised to see a significant effect in the women whose water contained atrazine levels far below the EPA’s standard of 3 parts per billion.
The research team was surprised to see a significant effect in the women whose water contained atrazine levels far below the EPA’s standard of 3 parts per billion.In Illinois water, the average concentration of atrazine was 0.7 parts per billion, several times lower than the averages recorded in previous and subsequent summers. Cragin said drought conditions in 2005 would have slowed runoff from farm fields.
The researchers did not examine whether the menstrual and hormonal changes reduced the women’s ability to become pregnant. However, estrogen levels and menstrual cycle characteristics are known to affect fertility.
“These types of changes to hormone concentration and ovarian function could potentially lead to problems with fertility,” said Emily Barrett, a reproductive health scientist at the University of Rochester in New York.
Hormonal changes also have been associated with greater risk of certain diseases such as osteoporosis, diabetes, heart disease and some cancers.
Though scientists are not sure how atrazine would disrupt hormone levels, some studies suggest that the chemical may block the production of estrogen in the body.
Hormonal changes have been associated with greater risk of certain diseases such as osteoporosis, diabetes, heart disease and some cancers.The small number of women involved in the study could increase the possibility that the differences between the two communities are due to chance. However, “to find a profoundly higher incidence of reproductive irregularities in such a small group of people suggests that something is definitely going on here,” said Laura Vandenberg, a reproductive scientist at Tufts University.
First registered as an herbicide in 1958, atrazine is used primarily to eliminate weeds on land where crops including corn and sorghum grow, but it is sometimes used on lawns and golf courses too.
In 2003, the EPA reevaluated the safety of atrazine and determined that the current safety standard of 3 parts per billion is sufficient to protect against hormonal effects of atrazine.
At the time, the EPA mandated Syngenta to begin monitoring roughly 100 community water systems nationwide for levels of the chemical in drinking water. Environmental groups criticized the decision because they said it allowed the chemical company to oversee itself.
Since 2003, more than 150 new studies raising concerns about the potential health effects of atrazine have been published. The European Union has since banned it due to safety concerns.
Women who drink water contaminated with low levels of the weed-killer atrazine may be more likely to have irregular menstrual cycles and low estrogen levels, scientists concluded in a new study.
The most widely used herbicide in the United States, atrazine is frequently detected in surface and ground water, particularly in agricultural areas of the Midwest. Approximately 75 percent of all U.S. cornfields are treated with atrazine each year.
The newest research, which compared women in Illinois to women in Vermont, adds to the growing scientific evidence linking atrazine to altered hormones.
The women from Illinois farm towns were nearly five times more likely to report irregular periods than the Vermont women, and more than six times as likely to go more than six weeks between periods. In addition, the Illinois women had significantly lower levels of estrogen during an important part of the menstrual cycle.
Tap water in the Illinois communities had double the concentration of atrazine in the Vermont communities’ water. Nevertheless, the water in both states was far below the federal drinking water standard currently enforced by the U.S. Environmental Protection Agency.
Approximately 75 percent of all U.S. cornfields are treated with atrazine each year. It also is sometimes used on lawns and golf courses to kill weeds.The amount of water consumed also seemed to make a difference: Women who said they drank more than two cups of Illinois tap water daily reported an even greater occurrence of irregular periods.
In recent years, some tests on lab animals have linked the herbicide to fertility issues, including altered hormone levels, delayed puberty and pregnancy loss.
Co-author Lori Cragin, an epidemiologist with Colorado State University at the time of the study, said the new findings fit with the results of the animal studies, as well as with some limited research that reported human effects.
In 2009, a study tied atrazine in drinking water to low birth weight in Indiana newborns. And in a study of more than 3,000 women enrolled in the Agricultural Health Study, those who described using atrazine and other pesticides had an increased risk of missed periods and bleeding between periods. The Agricultural Health Study is a nationwide project sponsored by the National Institutes of Health.
Studies in frogs suggest that atrazine, even at low levels, may affect development of the male reproductive system, decreasing fertility and in some cases leading to hermaphroditic frogs.
“In frogs, atrazine disrupts the balance between what it means to develop and function as a male or a female,” said Tyrone Hayes, a scientist from the University of California, Berkeley who studies the reproductive effects of pesticides in frogs.
In 2009, the EPA ordered another review in light of new studies. The agency is currently awaiting the results of an evaluation by a scientific advisory panel.
In the meantime, use of the herbicide continues to rise. In the first half of 2011 alone, Syngenta reported double-digit growth in sales, with atrazine as a high performer.
Some environmental groups and scientists are frustrated with the pace of the regulatory process when it comes to evaluating chemical safety.
“We can’t continue to allow the use of this chemical when we are seeing adverse effects on animals and people,” said Vandenberg.
Source : Environmental Health News
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