THE INTRODUCTIONMore than 1 billion pounds of pesticides are used in the U.S. each year, according to the study. Those pesticides are sprayed on agricultural fields and orchards, residential lawns, playgrounds and parks. And evidence suggests that, contrary to what the EPA claims, most of those pesticides are made from chemicals that are unsafe at any levels, because they are hormone disruptors.
Last September, the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (“OEHHA”) issued a notice of its intent to list glyphosate as a chemical “known to the state” to cause cancer. Listing glyphosate as a known carcinogen would subject the chemical to new consumer warnings and other requirements under California’s Safe Drinking Water and Toxic Enforcement Act of 1986, commonly known as Proposition 65.
THE EVIDENCEEnvironmental Health News:
Dozens of substances that can mimic or block estrogen, testosterone and other hormones are found in the environment, the food supply and consumer products, including plastics, pesticides and cosmetics. One of the biggest, longest-lasting controversies about these chemicals is whether the tiny doses that most people are exposed to are harmful.
In the new report, researchers led by Tufts University’s Laura Vandenberg concluded after examining hundreds of studies that health effects “are remarkably common” when people or animals are exposed to low doses of endocrine-disrupting compounds. As examples, they provide evidence for several controversial chemicals, including bisphenol A, found in polycarbonate plastic, canned foods and paper receipts, and the pesticide atrazine, used in large volumes mainly on corn.
The scientists concluded that scientific evidence “clearly indicates that low doses cannot be ignored.” They cited evidence of a wide range of health effects in people – from fetuses to aging adults – including links to infertility, cardiovascular disease, obesity, cancer and other disorders.
“Whether low doses of endocrine-disrupting compounds influence human disorders is no longer conjecture, as epidemiological studies show that environmental exposures are associated with human diseases and disabilities,” they wrote.
In addition, the scientists took on the issue of whether a decades-old strategy for testing most chemicals – exposing lab rodents to high doses then extrapolating down for real-life human exposures – is adequate to protect people.
They concluded that it is not, and so they urged reforms. Some hormone-like chemicals have health effects at low doses that do not occur at high doses.
“Current testing paradigms are missing important, sensitive endpoints” for human health, they said. “The effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.”
The report was published online Wednesday in the scientific journal Endocrine Reviews. Authors include scientists University of Missouri's Frederick vom Saal, who has linked low doses of bisphenol A to a variety of effects, Theo Colborn, who is credited with first spreading the word about hormone-disrupting chemicals in the late 1980s and University of California, Berkeley's Tyrone Hayes, who has documented effects of atrazine on frogs.
In many cases, chemical manufacturers still are asking “old questions” when they test the safety of chemicals even though “science has moved on,” she said. “Some of the testing paradigms have not advanced with the state of the science.” Birnbaum wrote an editorial on Wednesday referencing the new report.
Nevertheless, for most toxicologists, Birnbaum said the report does not offer a big shift from what they are doing. The NIEHS already conducts low-dose testing of chemicals, including looking for multi-generational effects such as adult diseases that are triggered by fetal exposures.
Several of the report’s authors have been criticized by some other scientists and industry representatives because they have become outspoken advocates for testing, regulating and replacing endocrine-disrupting compounds. The scientists, however, say they feel compelled to speak out because regulatory agencies are slow to act and they are concerned about the health of people, especially infants and children, and wildlife.
Industry representatives say that just because people are exposed to traces of chemicals capable of altering hormones doesn’t mean there are any harmful effects. They say that the studies are often contradictory or inconclusive.
Endocrinologists have long known that infinitesimal amounts of estrogen, testosterone, thyroid hormones and other natural hormones can have big health effects, particularly on fetuses. It comes as no surprise to them that manmade substances with hormonal properties might have big effects, too.
“There truly are no safe doses for chemicals that act like hormones, because the endocrine system is designed to act at very low levels,” Vandenberg, a postdoctoral fellow at Tufts University’s Levin Lab Center for Regenerative and Developmental Biology, told Environmental Health News.
But many toxicologists subscribe to “the dose makes the poison” conventional wisdom. In other words, it takes a certain size dose of something to be toxic. They also are accustomed to seeing an effect from chemicals called “monotonic,” which means the responses of an animal or person go up or down with the dose.
The scientists in the new review said neither of those applies to hormone-like chemicals.
“Accepting these phenomena should lead to paradigm shifts in toxicological studies, and will likely also have lasting effects on regulatory science,” they wrote.
In the report, the scientists were concerned that government has determined "safe" levels for “a significant number of endocrine-disrupting compounds” that have never been tested at low levels. They urged “greatly expanded and generalized safety testing.”
"The question is no longer whether these phenomena exist, but how to move forward and deal with them.”
Chemicals used in certain pesticides and as insulating material banned in the 1970s may still be haunting us, according to new research that suggests links between higher levels of exposure during pregnancy and significantly increased odds of autism spectrum disorder in children.
According to the research, children born after being exposed to the highest levels of certain compounds of the chemicals, called organochlorine chemicals, during their mother's pregnancy were roughly 80 percent more likely to be diagnosed with autism when compared to individuals with the very lowest levels of these chemicals. That also includes those who were completely unexposed.
Although production of organochlorine chemicals was banned in the United States in 1977, these compounds can remain in the environment and become absorbed in the fat of animals that humans eat, leading to exposure.
Michael C.R. Alavanja. "Pesticides Use and Exposure Extensive Worldwide." Rev Environ Health. 2009 Oct–Dec; 24(4): 303–309. PMCID: PMC2946087.
Laura N. Vandenberg, et al. "Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses." 2012. Endocrine Reviews 33:3. http://press.endocrine.org/doi/full/10.1210/er.2011-1050.
Melnick R, et al. "Summary of the National Toxicology Program's report of the endocrine disruptors low-dose peer review." Environ Health Perspect 110:427–431. PMCID: PMC1240807.
Kristen Lyall. "Polychlorinated Biphenyl and Organochlorine Pesticide Concentrations in Maternal Mid-Pregnancy Serum Samples: Association with Autism Spectrum Disorder and Intellectual Disability." Environ Health Perspect; doi:10.1289/EHP277.
Christopher Portier, et al. "Differences in the carcinogenic evaluation of glyphosate between the International Agency for Research on Cancer (IARC) and the European Food Safety Authority (EFSA)". J Epidemiol Community Health. doi:10.1136/jech-2015-207005.
THE VERDICTBiological Diversity:
A full analysis of mixture toxicity needs to be taken into account for both the human health and ecological risk assessments. When patent applications or other data demonstrate synergistic toxicity to target organisms, that synergy needs to be assumed for all other nontarget organisms within that taxon. For instance if a mixture results in synergistic toxicity to a target insect, like an aphid, then that synergy needs to be assumed for all insects and possibly all other invertebrates in the ecological risk assessment unless available data indicate otherwise.
This would be consistent with EPA’s current use of surrogate species to estimate toxicity to other species within the same taxon for the human health and ecological risk assessments. This is one way that the EPA can begin to take into account mixture toxicity given the extensive data gaps that are currently present.
“There’s evidence that diet is one route of exposure to pesticides, and you can reduce your exposure by choosing organic food,” said the lead author, Asa Bradman, associate director of the Center for Environmental Research and Children’s Health at the University of California, Berkeley. “But I would never say that conventional fruits and vegetables are unsafe. They’re all healthy.”
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