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Two recent studies, both done in California, looked at different aspects of pesticide exposure. They highlight how people can be exposed to pesticides in the air they breathe, especially if they live in areas where pesticides are heavily applied (such as farms). But keep in mind that even in suburbia, every time a neighbor applies pesticides on the lawn or trees - there is drift, and so you are also exposed (e.g., breathing it, droplets on the skin).

The first study found that pregnant women with high pesticide exposure (living in areas near farms using pesticides) had increases in adverse birth outcomes (low birth weight, shorter pregnancy length, preterm birth, birth defects or abnormalities). No effects were seen with low pesticide exposure. But note that these results are what could be seen at birth - they do not include effects that can only be seen later, such as delayed development, learning disabilities, lower intelligence, asthma, autism - all effects found in some studies.

The other was a California Department of Pesticide Regulation (CDPR) 2016 report on air monitoring results (from 6 sites) of 32 chemicals (pesticides and breakdown products) in California. Some pesticides were not detected, some were only at trace amounts, and some were detected at higher amounts  - and the amounts fluctuated over the year and from site to site. [NOTE: They did not monitor for 2 widely used pesticides: glyphosate, which is in Roundup, and 2,4-D. Hmm...]. A Kern County high school monitoring site showed levels of the pesticide chlorpyrifos more than 18 times higher than EPA's "level of concern for pregnant women" - but yet these levels are considered OK for the general public.

Chlorpyrifos is "controversial" in that scientists (including EPA scientists), medical professionals, and farmworker organiztions asked that its use be banned due to its serious health effects on humans, but this year EPA chief Scott Pruitt refused to do so (he gave in to pesticide industry lobbying). The bottom lineWhat effect do the mixtures of pesticides (at chronic low levels) that we're exposed to have on us? Unknown. 

From Medical Xpress: Researchers unravel the negative effects of pesticide exposure on birth outcomes

Although common opinion holds that exposure to pesticides increases adverse birth outcomes, the existing body of scientific evidence is ambiguous..... A new study by researchers at UC Santa Barbara addresses the issue in a novel way—by analyzing birth outcomes in California's San Joaquin Valley. With more than one-third of the country's vegetables and two-thirds of its fruits and nuts produced there, the San Joaquin Valley, not surprisingly, is a heavy pesticide-use region. The UCSB team investigated the effect of exposure during pregnancy in this agriculturally dominated area and observed an increase in adverse outcomes accompanying very high levels of pesticide exposure

"For the majority of births, there is no statistically identifiable impact of pesticide exposure on birth outcome," said lead author Ashley Larsen, an assistant professor in UCSB's Bren School of Environmental Science & Management. "Yet mothers exposed to extreme levels of pesticides, defined here as the top 5 percent of the pesticide exposure distribution, experienced between 5 and 9 percent increases in the probability of adverse outcomes with an approximately 13-gram decrease in birth weight."

Using individual birth certificate records for more than 500,000 single births between 1997 and 2011, coupled with pesticide use data at a fine spatial and temporal scale, the scientists were able to determine if residential agricultural pesticide exposure during gestation—by trimester and by toxicity—influenced birth weight, gestational length or birth abnormalities.

They found negative effects of pesticide exposure for all birth outcomes—birth weight, low birth weight, gestational length, preterm birth, birth abnormalities—but only for mothers exposed to very high levels of pesticides—the top 5 percent of the exposure distribution in this sample.... Numerous chemicals are used daily in close proximity to residential areas, making it difficult to ascertain a specific responsible agent. As a result, in this study, the researchers looked at the combined results from all pesticides used in the region[Original study.]

Excerpts from Beyond Pesticides: Neurotoxic Pesticide Detected in Air at High Levels in California County

The California Department of Pesticide Regulation (CDPR) released its 2016 air monitoring data where it was revealed that chlorpyrifos air concentrations for a one-month period at the air monitoring site on the campus of Shafter High School in Kern County was 39.4 nanograms per cubic meter (ng/m3) – more than 18 times higher than EPA’s level of concern for pregnant women (2.1 ng/m3).  Shafter High School is some distance from fields in an area where chlorpyrifos use is not as high as in other parts of Kern County or elsewhere in California. 

High chlorpyrifos levels at a school means that children and unsuspecting teachers and parents, especially those that may be pregnant, are breathing in unusually high levels of chlorpyrifos. Children exposed to high levels of chlorpyrifos have developmental delays, attention problems, attention-deficit/hyperactivity disorder problems, and pervasive developmental disorders.

Several studies have found that when children eat organic foods, especially fruits and vegetables, the amount of pesticides in their bodies declines significantly. Most organophosphorus pesticides have been phased out for residential use, but they are still widely used in agriculture, and so these pesticides are detected in both foods and people. This latest study looked at 20 children living in urban Oakland, Calif., and 20 in the agricultural community of Salinas, about 100 miles south. The children (between 3 - 6 years of age) ate a conventional diet for four days and an organic diet for seven days and then returned to conventional foods for five days. Their urine was collected daily and analyzed for pesticides, specifically by looking at pesticide metabolites (pesticide breakdown products).

Several classes of pesticides were frequently detected, for they were found in more than 72 percent of their urine samples, and 2,4-D was detected in 90% of samples. Of the six most frequently detected pesticides, two decreased by nearly 50 percent when children were on the organic diet, and levels of the common herbicide 2,4-D fell by 25 percent. Amounts of some pesticides were not significantly lower on the organic diet, but these were pesticides associated with use around homes for pest control, and not on foods (e.g., pyrethroids, diazinon, malathion). Bottom line: eat as many organic foods as possible to lower pesticide levels in the  body. To further reduce pesticide levels in the body - avoid pesticide use around the home and garden. Instead, use least toxic IPM (Integrated Pest Management) or organic pest control and organic gardening.

From Medical Xpress: Organic produce means reduced pesticides in kids, study shows

New research out of the Center for Environmental Research and Children's Health at UC Berkeley shows that switching from conventional to organic fruits and vegetables, even for just a few days, significantly reduces pesticide levels in children's bodies.

Twenty children in Oakland, California and 20 in Salinas, California, all 3 to 6 years old, had their urine tested for 16 days during the study. For the first four, they ate conventional produce, for the next seven their diet was organic, and then conventional for the last five. The levels of several pesticides that showed up in daily testing dropped by one-quarter to one-half during the organic stretch.

Excerpts from the original study from Environmental Health Perspectives: Effect of Organic Diet Intervention on Pesticide Exposures in Young Children Living in Low-Income Urban and Agricultural Communities

Recent organic diet intervention studies suggest that diet is a significant source of pesticide exposure in young children....We aimed to determine whether consuming an organic diet reduced urinary pesticide metabolite concentrations in 40 Mexican-American children, 3–6 years of age, living in California urban and agricultural communities. In 2006, we collected urine samples over 16 consecutive days from children who consumed conventionally grown food for 4 days, organic food for 7 days, and then conventionally grown food for 5 days. We measured 23 metabolites, reflecting potential exposure to organophosphorous (OP), pyrethroid, and other pesticides used in homes and agriculture.

For six metabolites with detection frequencies > 50%, adjusted geometric mean concentrations during the organic phase were generally lower for all children, and were significant for total dialkylphosphates (DAPs) and dimethyl DAPs (DMs; metabolites of OP insecticides) and 2,4-D (2,4-dichlorophenoxyacetic acid, a herbicide), with reductions of 40%, 49%, and 25%, respectively (p < 0.01). Chemical-specific metabolite concentrations for several OP pesticides, pyrethroids, and herbicides were either infrequently detected and/or not significantly affected by diet.

Although most residential uses of many organophosphorus (OP) pesticides, including chlorpyrifos and diazinon, have been phased out since the mid-2000s due to potential health risks to children, they have continued to be used in agriculture [U.S. Environmental Protection Agency (EPA) 2000, 2001]. The use of OP pesticides in agriculture could result in ingestion of residues in food, and recent studies suggest that dietary intake of produce and juices may account for a significant proportion of OP pesticide exposure in young children (Lu et al. 2006b, 2008; Morgan et al. 2005; Smith-Spangler et al. 2012; Wilson et al. 2003). Some of the best evidence supporting these findings includes results from diet intervention studies where significant reductions in excreted urinary pesticide metabolites were observed in young children when they consumed an organic diet (Lu et al. 2006b, 2008)....The lower urinary pesticide metabolite concentrations found in children eating organic diets is consistent with food residue monitoring data that has shown lower pesticide residue levels in organic versus conventionally grown food [Baker et al. 2002; U.S. Department of Agriculture (USDA) 2008].

Other factors associated with children’s cumulative pesticide exposures include socioeconomic status and location of residence. For example, low-income children may experience higher exposures to pesticides, particularly pyrethroids, because of poor housing quality and associated pest infestations and home pesticide use (Bradman et al. 2005a; Quirós-Alcalá et al. 2011; Whyatt et al. 2002). Children living in agricultural areas, compared with children living in non-agricultural suburban areas, are exposed to higher ambient and residential contamination from drift or volatilization from nearby agricultural applications and take-home residue by farmworking parents (Bradman et al. 2011; Harnly et al. 2009;Lu et al. 2000; Quirós-Alcalá et al. 2011).

Our finding that an organic diet was not associated with a significant reduction in pyrethroid metabolite (3-PBA) excretion for all children is not surprising given that these pesticides are primarily used in and around homes and not commonly applied to food crops; the finding is also consistent with Lu et al. (2006a), who reported that residential use is a more significant pyrethroid exposure factor for children than a conventional diet. 

Several studies indicate that dietary intake is a potential route of exposure for herbicides.....Overall, these studies indicate that 2,4-D may be present in food and support our finding that the lower levels observed in our population during the organic diet phase were attributable to lower dietary exposure.

In summary, consistent with other studies, urinary 2,4-D and two measures of OP pesticide exposure (total DMs and total DAP metabolites) were lower in children eating an organic diet. Other frequently detected metabolites for pyrethroids, diethyl OP pesticides, and the herbicide metolachlor were not significantly lower during the organic diet phase. Further, several compound-specific herbicide and OP pesticide metabolites had low detection frequencies, indicating that diet was not an important exposure source for these pesticides (e.g., diazinon, malathion) in this population. Last, independent of diet, most frequently detected metabolites were generally higher in Salinas compared with Oakland children, with DMs and metolachlor at or near significance (p = 0.06 and 0.03, respectively), suggesting additional sources of pesticide exposure for children living in agricultural communities.

Children's brain development being harmed by chemicals in the environment - both before birth and in childhood -  is such an important topic that here are excerpts from two articles about the same report that was just released (in Lancet Neurology).  From Time:

Children Exposed to More Brain-Harming Chemicals Than Ever Before

In recent years, the prevalence of developmental disorders such as autism, attention deficit/hyperactivity disorder (ADHD) and dyslexia  have soared. While greater awareness and more sophisticated diagnoses are partly responsible for the rise, researchers say the changing environment in which youngsters grow up may also be playing a role.

In 2006, scientists from the Harvard School of Public Health and the Icahn School of Medicine at Mount Sinai identified five industrial chemicals responsible for causing harm to the brain — lead, methylmercury, polychlorinated biphenyls (found in electric transformers, motors and capacitors), arsenic (found in soil and water as well as in wood preservatives and pesticides) and toluene (used in processing gasoline as well as in paint thinner, fingernail polish and leather tanning). Exposure to these neurotoxins was associated with changes in neuron development in the fetus as well as among infants, and with lower school performance, delinquent behavior, neurological abnormalities and reduced IQ in school-age children.

Now the same researchers have reviewed the literature and found six additional industrial chemicals that can hamper normal brain development. These are manganese, fluoride, chlorpyrifos, dichlorodiphenyltrichloroethane, tetrachloroethylene and polybrominated diphenyl ethers. Manganese, they say, is found in drinking water and can contribute to lower math scores and heightened hyperactivity, while exposure to high levels of fluoride from drinking water can contribute to a seven-point drop in IQ on average. The remaining chemicals, which are found in solvents and pesticides, have been linked to deficits in social development and increased aggressive behaviors.

But they say the growing body of research that is finding links between higher levels of these chemicals in expectant mothers’ blood and urine and brain disorders in their children should raise alarms about how damaging these chemicals can be. The developing brain in particular, they say, is vulnerable to the effects of these chemicals, and in many cases, the changes they trigger are permanent. The consequence of such brain damage is impaired [central nervous system] function that lasts a lifetime and might result in reduced intelligence, as expressed in terms of lost IQ points, or disruption in behavior,” they write in their report, which was published in the journal Lancet Neurology.

Same report, from Science Daily: Growing number of chemicals linked with brain disorders in children

"The greatest concern is the large numbers of children who are affected by toxic damage to brain development in the absence of a formal diagnosis. They suffer reduced attention span, delayed development, and poor school performance. Industrial chemicals are now emerging as likely causes," said Philippe Grandjean, adjunct professor of environmental health at HSPH.

The study outlines possible links between these newly recognized neurotoxicants and negative health effects on children, including:  - Manganese is associated with diminished intellectual function and impaired motor skills  - Solvents are linked to hyperactivity and aggressive behavior - Certain types of pesticides may cause cognitive delays.

Grandjean and co-author Philip Landrigan, Dean for Global Health at Mount Sinai, also forecast that many more chemicals than the known dozen or so identified as neurotoxicants contribute to a "silent pandemic" of neurobehavioral deficits that is eroding intelligence, disrupting behaviors, and damaging societies. But controlling this pandemic is difficult because of a scarcity of data to guide prevention and the huge amount of proof needed for government regulation. "Very few chemicals have been regulated as a result of developmental neurotoxicity," they write.

The authors say it's crucial to control the use of these chemicals to protect children's brain development worldwide. They propose mandatory testing of industrial chemicals and the formation of a new international clearinghouse to evaluate industrial chemicals for potential developmental neurotoxicity.