by Elizabeth Grossman
“Organic, schmorganic,” wrote New York Times foreign editor and International Herald Tribune editor-at-large Roger Cohen, summing up his “takeaway” from the study by Stanford University researchers that examined studies comparing the nutritional value and pesticide residues in organic and “conventionally” grown food. The study concluded that evidence was lacking to show that organic food is more nutritious than conventionally grown food, but that organic food did have about 30 percent fewer pesticide residues. “I’d rather be against nature and have more people better fed,” wrote Cohen, “And I trust the monitoring agencies to ensure pesticides are used at safe levels – a trust the Stanford study found to be justified.”
Those pesticide residues and what constitutes safe levels of exposure, however, take on new significance in light of the recent research by Virginia Rauh and colleagues at the Columbia University Mailman School of Public Health. Rauh, who presented her latest study during a September 12 webinar hosted by the US Environmental Protection Agency (EPA) and National Institute of Environmental Health Sciences (NIEHS), has found a strong association between prenatal pesticide exposure and adverse impacts on behavior, brain structure, cognitive ability, and neurodevelopment. Her research also indicates that the brain abnormalities triggered by this pesticide exposure appear to occur at levels below the current EPA threshold for toxicity.
Rauh and colleagues have been studying the effects of prenatal exposure to the pesticide known as chlorpyrifos on New York City children living in Harlem and the South Bronx whose mothers likely encountered the chemical when it was used in indoor pest control. Chlorpyrifos, which belongs to a class of pesticides known as organophosphates, has been on the US market for more than 40 years. It is used worldwide, and kills insects by affecting their nervous systems. Chlorpyrifos has been used in indoor pest control, in commercial agriculture, in lawn care products, for termite control, and in domestic pet flea and tick collars. Concern over chlorpyrifos and other organophosphates’ potential health effects, particularly on children, led to an EPA ban on the use of several, including chlorpyrifos, for indoor use beginning in 2001.The children in Rauh’s study were exposed before the ban took effect.
Organophosphates in the fields
While now off the market for use indoors, chlorpyrifos and other organophosphate pesticides continue to be used agriculturally. In the US in 2002, 10 million pounds of chlorpyrifos were used in agriculture; in 2009, more than one million pounds of chlorpyrifos were used in California alone. In that state’s Salinas Valley, University of California scientists have been studying children prenatally exposed to these chemicals. Both the Columbia and California researchers found these children’s IQ to be notably reduced by organophosphate exposure; that the higher the exposure, the lower the IQ score. Both also found there was no threshold or base measured level of pesticide exposure that did not produce an effect.
In their latest research, Rauh and colleagues have looked at how this exposure is affecting children’s brains physically. Their study is the first to use MRI (magnetic resonance imaging) to identify structural evidence for cognitive deficits in humans, though this has been done previously in animal studies. Strikingly, what they saw in physical brain alterations – thinning in some areas and abnormal enlargement in others – is consistent with effects that would produce the IQ reductions measured in the children who Rauh’s study has been following since birth. The brain alterations observed, explained Rauh, are in the parts of the brain linked to working memory function, language, and behavior including emotion, reward, and inhibition control, and attention.
Last spring researchers at the Mailman School reported that these children, who were exposed to chlorpyrifos prenatally through the pesticide’s use indoors, had reduced IQ scores at age 7. “These observed deficits in cognitive functioning at 7 years of age could have implications for school performance,” Rauh explained in a Columbia University newsletter. “Working memory problems may interfere with reading comprehension, learning and academic achievement, even if general intelligence remains in the normal range,” said Rauh.
The new research examining chlorpyrifos exposure’s impact on physical brain development also indicates that this exposure may also eliminate or reverse the male-female differences ordinarily present in the brain – at least at a time well before puberty. “The brain abnormalities suggest that prenatal chlorpyrifos exposure, even at very low levels that would be consistent with standard agricultural use, show a significant association with structural changes in the developing brain, including sex-specific effects that persist into middle childhood,” explained Rauh during the EPA/NIEHS webinar.
Rauh also explained that the EPA’s current safety standards for chronic exposure to chlorpyrifos at 30 nanograms per kilogram of bodyweight are based on a particular mechanism through which chlorpyrifos inhibits an enzyme vital to healthy brain development. The adverse impacts to brain development Rauh and colleagues documented, however, appear to be happening at lower levels of exposure than EPA considers safe. As appeared to be the case with IQ score effect, the brain alterations appear to be occurring levels of exposure so low that Rauh and colleagues say there may be no threshold below which exposure does not alter brain or neurodevelopment. This means other mechanisms besides this particular enzyme may be involved. It also means, said Rauh, that the EPA standards for chlorpyrifos exposure may be too high to be protective, at least where prenatal and children’s exposure is concerned.
Despite the indoor use ban and a recent drop in overall organophosphate pesticide use, chlorpyrifos continues to be widely used not only in agriculture, but also on highway medians, golf courses, some parks, and as a wood treatment. People can be exposed as the chemical drifts during use but also, say the Columbia researchers, by eating treated fruits and vegetables.
The “organic ideology is an elitist, pseudoscientific indulgence shot through with hype,” wrote Roger Cohen in his New York Times op-ed, “a class-driven decision that demonstrates how much you love your offspring but whose overall impact on society is debatable.” The low-income parents of the elementary school children in Harlem, the South Bronx, and California’s Central Valley agricultural communities might beg to differ, knowing that pesticide exposure is making it harder for their children to succeed in school.
Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry, High Tech Trash: Digital Devices, Hidden Toxics, and Human Health, and other books. Her work has appeared in a variety of publications including Scientific American, Salon, The Washington Post, The Nation, Mother Jones, Grist, and the Huffington Post. Chasing Molecules was chosen by Booklist as one of the Top 10 Science & Technology Books of 2009 and won a 2010 Gold Nautilus Award for investigative journalism.
Thank you for such a revealing and important contribution. Another part of the Stanford study also needs to be reexamined. You mention its supposed finding that "organic food did have about 30 percent fewer pesticide residues." This greatly understates the truth, though the Stanford report and the Stanford press release both make this false statement. The Stanford authors reported an overall 38% risk of one or more pesticide residues in conventional foods compared to only 7% in organic foods, an 82% lower risk (incidence). The Stanford authors reported this finding very misleadingly as a 30% "Risk Difference," calculated as 38% minus 7% (except for rounding errors). Then in their discussion they dropped the odd "difference" terminology and stated falsely that "conventional produce has a 30% higher risk for pesticide contamination than organic produce." They should have said a 540% higher risk (38%/7%). Similarly regarding the incidence of multi-antibiotic-resistant bacteria, they found a 300% higher risk in conventional than organic foods, but they misleadingly, and in some places falsely, reported this as a 33% higher risk, again calculated as a "Risk Difference" = 49% minus 16% (implied by data in Fig. 3). It is difficult to explain these deceptive and false reports as other than an intent to mislead journal readers and the public.
Correction: Near the end I referred to Fig. 3; it should be Fig. 5. (FYI, I am a research scientist retired from the Univ. of Texas at Austin.)
I think that everything said in the above article makes good sense but the most important fact is left out. The highest level of prenatal exposure occurs to the children of farm workers, not the children of consumers. As a consumer, the most important reason I buy organic food is not for MY children's health. It is for the health of the children of farm workers. Roger Cohen misses this too. It is terribly elitist of him not to be concerned with the health of farm workers and their children. There is plenty of good science supporting the ill effects of pesticides on farm workers
Int J Hyg Environ Health. 2012 Sep;215(5):496-501. Epub 2011 Nov 26.
Brain cancer mortality among farm workers of the State of Rio de Janeiro, Brazil: a population-based case-control study, 1996-2005.
Miranda-Filho AL, Monteiro GT, Meyer A.
Environmental and Public Health Program, National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil. email@example.com
Farm workers seem to be at an increased risk of developing some cancers, notably in the brain. One of the hypotheses rose to explain such elevated risk is the intense exposure to pesticides.
To estimate the brain cancer mortality risk among agricultural workers exposed to pesticides in the State of Rio de Janeiro, Brazil.
A case-control study based on death certificates of males, 18 years or older, resident in the State Rio de Janeiro who died between 1996 and 2005. Cases (n=2040) were defined as individuals with brain cancer as the underlying cause of death. For each case two controls (n=4140) were randomly selected in the same database, matched for age group and region of residence. Besides the descriptive analysis, crude and adjusted odds ratios and mortality odds ratio (MOR) according to quartiles of potential exposure to pesticides, were calculated.
Agricultural workers showed higher brain cancer mortality risk estimates when compared with non-farm workers (aOR: 1.82, 95% CI 1.21-2.71). In addition, the magnitude of this association was higher among white patients, with higher education, and residence in an agricultural region.
This study suggests an association between agricultural work and brain cancer mortality in Rio de Janeiro state. It also suggests that pesticide exposure may play a role in such risk.
J Med Toxicol. 2011 Jun;7(2):164-71.
Surveillance data on pesticide and agricultural chemical releases and associated public health consequences in selected US states, 2003-2007.
Saw L, Shumway J, Ruckart P.
Utah Department of Health, Salt Lake City, UT, USA.
While pesticides and agricultural chemicals are used to increase crop production and to reduce the spread of disease, their toxic nature also has the potential to threaten human health. Releases of pesticides and agricultural chemicals have resulted in human illness and death. This analysis examines releases of pesticides and agricultural chemicals and their associated injuries captured by the Hazardous Substances Emergency Events Surveillance (HSEES) system from 2003-2007.
Simple descriptive statistics are presented. Comparisons were made to data from all HSEES events when possible.
Analysis of the data shows that farm workers are at particular risk for injury and that the most frequent months for releases of pesticides and agricultural chemicals were the spring planting months of April through June. Releases of pesticides and agricultural chemicals occurred more often during transport, had higher frequencies of patient decontamination associated with them, and lower frequencies of evacuation and shelter-in place orders compared with all HSEES events.
Since exposures are precipitated by behavioral and environmental factors, especially in occupational settings, future interventions targeting employers, and transporters of agricultural chemicals, as well as physicians, are recommended. These interventions should be customized to fit local conditions.
Neurotoxicology. 2011 Mar;32(2):268-76. Epub 2010 Dec 21.
Correlating neurobehavioral performance with biomarkers of organophosphorous pesticide exposure.
Rohlman DS, Anger WK, Lein PJ.
Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, OR 97239, USA. firstname.lastname@example.org
There is compelling evidence that adverse neurobehavioral effects are associated with occupational organophosphorous pesticide (OP) exposure in humans. Behavioral studies of pesticide applicators, greenhouse workers, agricultural workers and farm residents exposed repeatedly over months or years to low levels of OPs reveal a relatively consistent pattern of neurobehavioral deficits. However, only two studies have demonstrated a link between neurobehavioral performance and current biomarkers of OP exposure including blood cholinesterase (ChE) activity and urinary levels of OP metabolites. A variety of reasons may explain why so few studies have reported such correlations, including differing individual and group exposure histories, differing methodologies for assessing behavior and exposure, and lack of a reliable index of exposure. Alternatively, these data may suggest that current biomarkers (ChE, urine metabolites) are neither predictive nor diagnostic of the neurobehavioral effects of chronic OP pesticide exposures. This review focuses on the evidence that neurobehavioral performance deficits are associated with occupational OP pesticide exposure and concludes that research needs to return to the basics and rigorously test the relationships between neurobehavioral performance and both current (ChE and urine metabolites) and novel (e.g., inflammation and oxidative stress) biomarkers using human and animal models. The results of such studies are critically important because OP pesticides are widely and extensively used throughout the world, including situations where exposure controls and personal protective equipment are not routinely used.
Thanks, Darius, for this reference and your point. The children in the California pesticide exposure study live in agricultural communities in the Salinas Valley so their exposure is indeed related to what their mothers were exposed to by living and working where these chemicals are used. So I think these exposure could be classified as occupationally related. And that is indeed where these continuing exposures are occurring.
Seeing as the majority of commercial GM crops are designed to cause increased use of pesticides, perhaps now some of you will be less quick to label we who are anti-GM as being luddites?
Yikes, it's a good thing the people and the families who were harmed were fully compensated financially. After all, if harms like this are fully compensated that puts them on the accounting books. If it drives a company bankrupt or something, all it means is that the harm they were doing to society exceeded the benefits. So that's good then.
Granted there may be some argument to be made that some form of insurance scheme to prevent the event of such problems unexpectedly, despite honest efforts to account for them, bankrupting or harming otherwise promising businesses, or making it infeasible to engage in production and sale of pesticides like this etc. would be necessary, as there is always risk involved in technological progress.
But ultimately it comes down to net benefit or net harm, and full compensation ensures accurate accounting, which is what we all want. It's much better than letting corporations keep the profits from what they do, but force others to suffer the costs of such downsides, after all.
We must be making them nervous by gaining market share and not buying all those industrial chemicals!