16
Sep
Persistent Organic Pollutants, including Banned Pesticides, Remain Present in all Fetal Organs Regardless of Maternal Chemical Contamination
(Beyond Pesticides, September 16, 2021) A study published in Chemosphere finds persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), are present in the serum and placenta of pregnant mothers, as well as multiple fetal organs. Many studies indicate prenatal and early-life exposure to environmental toxicants increases susceptibility to diseases, from learning and developmental disabilities to cancer. However, this study is one of the first to demonstrate the presence of chemical toxicants in fetal tissue that are not present in maternal serum or placental samples. Prenatal development is one of the most vulnerable periods of exposure when the fetus is most susceptible to the harmful effects of chemical contaminants. Therefore, studies like these help government and health officials better identify fetal exposure contaminants and subsequent health concerns otherwise missed by current chemical monitoring methods. The researchers note, “These findings call for further evaluation of the current matrices used to estimate fetal exposure and establish a possible correction factor for a more accurate assessment of exposure in utero. We disclose the full data set on individual exposure concentrations to assist in building in silico models for prediction of human fetal exposure to chemicals.”
Several studies associate early-life exposure to toxic chemicals with adverse birth/health effects. However, fetal exposure measurements typically use maternal and placenta chemical concentrations rather than actual fetal exposure. Researchers used tandem mass spectrometry to measure chemical concentrations from maternal blood and placenta samples, as well as the liver, heart, lungs, brain, and fatty (adipose) tissues of fetuses. Using gas chromatography, the researchers tested for concentrations of nine different OCPs, ten different PCBs, and three different PBDEs. The cohort included women from 20 pregnancies who gave birth to a stillborn infant. Furthermore, scientists incorporated data from fetal exposure to perfluoroalkyl substances (PFASs) in the same cohort.
All 22 POPs are detectable in fetal fatty tissue samples regardless of chemical detection in the mother. Chemical concentrations are highest among later gestations (pregnancy), male infants, and pregnancies with standard placental function. Of chemical measurements, organochlorine pesticides are present in the highest amount in tissue and blood serum samples, followed by PCBs and PFAS. Adipose (fatty) tissue within the fetal organs has the highest chemical burden, while the brain has the lowest. Overall, more chemicals are detectable in fetal tissue samples than maternal blood/placenta samples.
Environmental contaminants like pesticides are ubiquitous in the environment, with 90 percent of Americans having at least one pesticide compound in their body. Although the 2001 Stockholm Convention treaty bans persistent organic pollutants (POPs) like well-known organochlorine compounds, these chemicals are still the primary pollutants of concern (UNEP, 2009). Their persistence and toxicity adversely affect environmental and biological health. These pollutants have a global distribution, with evaporation and precipitation facilitating long-range atmospheric transport, deposition, and bioaccumulation of hazardous chemicals in the environment. The U.S. was a signatory to the treaty, but U.S. Senate never ratified it, relegating U.S. officials to observer status. While various POPs on the Stockholm Convention annex lists are no longer manufactured or utilized, many of these chemical compounds remain in soils, water (solid and liquid), and the surrounding air at levels exceeding U.S. Environmental Protection Agency (EPA) standards. Therefore, individuals still encounter various POPs at varying concentrations, adding to the toxic body burden of those toxic chemicals currently in use.
Pesticides’ presence in the body has implications for human health, especially during vulnerable life stages like childhood, puberty, pregnancy, and old age. Pesticide exposure during pregnancy is of specific concern as health effects for all life stages can be long-lasting. Just as nutrients are transferable between mother and fetus, so are chemical contaminants. Studies find pesticide compounds present in the mother’s blood can transfer to the fetus via the umbilical cord. Furthermore, pregnant women already have over detectable 100 chemicals in blood and umbilical cord samples, including banned POPs. However, 89 percent of these chemical contaminants are from unidentified sources, lack adequate information, or were not previously detectable in humans. Therefore, pesticide exposure during pregnancy has implications for both mother and child’s health. Many studies indicate prenatal and early-life exposure to environmental toxins increases susceptibility to disease. A 2020 study finds the first few weeks of pregnancy are the most vulnerable periods during which prenatal exposure to pesticides can increase the risk of the rare fetal disorder holoprosencephaly. This disorder prevents the embryonic forebrain from developing into two separate hemispheres. Moreover, women living near agricultural areas experience higher exposure rates that increase the risk of birthing a baby with abnormalities. Some of these birth abnormalities include acute lymphoblastic leukemia and Attention-Deficit/Hyperactivity Disorder (ADHD). Even regular household pesticide use during pregnancy can increase nephroblastoma (kidney cancer) and brain tumor risk in children.
Pesticide exposure not only poses a risk to mothers and their offspring but also future generations. Studies find that although glyphosate (herbicide) exposure has a negligible impact on pregnant rats’ health, incidents of prostate, ovarian, and kidney cancer increase in the two subsequent generations. However, chemical exposure encompasses more than just current-use, toxic pesticides like glyphosate. The metabolites (or breakdown products) of many long-banned pesticides still impart adverse effects on human health. Researchers at Drexel University report that higher levels of some organochlorine compounds, like DDT, during pregnancy are associated with autism spectrum disorder (ASD) and intellectual disability (ID). Since many organochlorine compounds have long been banned in the U.S., the ongoing poisoning and contamination underscores how pervasive and persistent these chemicals are and their continued adverse impact on human health.
Not only are these compounds readily present in soil and water samples, but they are also in arctic ice. Therefore, the accompanying glacial melt from the climate crisis will only increase chemical bioavailability in the environment. The increasing ubiquity of pesticides is concerning to public health advocates because they say that current measures safeguarding against pesticide use do not adequately detect and assess total environmental chemical contaminants.
This study is one of the first to demonstrate differences in chemical contamination between fetus and mother. The results indicate that current pesticide detection methods for fetal exposure fail to capture the full scope of chemical detection. Numerous studies indicate chemical exposure mainly stems from dietary exposure, like food and drinking water, and researchers caution that there are hundreds to thousands of chemicals humans are likely to encounter that the study did not assess. The scientific literature demonstrates pesticides’ long history of severe adverse effects on human health (i.e., endocrine disruption, cancer, reproductive/birth problems, neurotoxicity, loss of biodiversity, etc.) and wildlife and biodiversity. There is a growing consensus that exposure to environmental toxicants before pregnancy can impair fertility, pregnancy, and fetal development. These adverse effects can continue into childhood and adulthood and may have multigenerational consequences. Therefore, researchers stress that future studies must evaluate chemical exposure within the fetus and not only rely on maternal or placental exposure.
The study notes sex-specific differences in birth outcomes between boys and girls. Compared to females, male fetuses have higher concentrations of POPs, resulting in a decrease in birth weight. Differences in placental function between male and female fetuses may play a role in chemical concentration distribution. Pregnancies with male fetuses have lower vascular resistance allowing greater blood flow and higher transfer of chemical concentrations. However, female fetuses display higher rates of learning and developmental disabilities, including attention-deficit/hyperactivity disorder (ADD/ADHD)upon PFAS exposure. Thus, the scientists suggest sex-specific distribution of chemicals may play a role in sexually dimorphic birth outcomes.
This study is not the first to demonstrate sex-specific effect of pesticide exposure. In 2017, scientists presented a study at the 99th meeting of the Endocrine Society demonstrating exposure to commonly used pyrethroid insecticides results in the early onset of puberty in boys. Furthermore, a 2021 study demonstrates exposure to current-use pesticides like organophosphates pose a greater health risk to women. Women with organophosphate exposure are more likely to develop cardiovascular disease, bronchitis, asthma, and various cancers. Given recent data on the rise in use of these chemicals for household pest control, both researchers and advocates are concerned about the range of implications these chemicals could be having on young children in the U.S. and abroad. Previous research finds these chemicals are associated with behavioral problems in children, including externalizing and internalizing disorders, ADHD, and delayed cognitive and motor development. Proximity to heavy use of these chemicals in agriculture is associated with an 87% increased risk of a child developing autism when applied during pregnant mother’s third trimester. Considering rates of preterm births, miscarriages/stillbirths, and birth malformations are increasing, it is necessary to assess chemical exposure effect on mothers and offspring to safeguard future generations’ health.
Doctors and pediatricians strongly agree that pregnant mothers should avoid pesticide exposure during critical development periods. Exposure concerns about POPs are increasing significantly, especially for adults and children more vulnerable to their toxic effects. Moreover, many contaminants are subject to regulatory standards that do not fully evaluate disease implications associated with exposure. Advocates say that addressing the manufacturing and use of pesticides is essential to mitigate risks from chemical exposure to toxic pesticides. Therefore, advocates urge that policies strengthen pesticide regulations and increase research on the long-term impacts of pesticide exposure. Beyond Pesticides tracks the most recent studies related to pesticide exposure through the Pesticide Induced Diseases Database (PIDD). This database supports the clear need for strategic action to shift away from pesticide dependency. For more information on the multiple harms of pesticide exposure, see PIDD pages on Birth/Fetal Effects, Sexual and Reproductive Dysfunction, Body Burdens, and other diseases. To learn more about how the lack of adequate pesticide regulations can adversely affect human and environmental health, see Beyond Pesticides’ Pesticides and You article “Highly Destructive Pesticide Effects Unregulated.”
One way to reduce human and environmental contamination from pesticides is buying, growing, and supporting organic. Numerous studies find that levels of pesticide metabolites in urine significantly drop when switching to an all-organic diet. Furthermore, given the wide availability of non-pesticidal alternative strategies, families and agro-industry workers alike can apply these methods to promote a safe and healthy environment, especially among chemically vulnerable individuals. For more information on how organic is the right choice for consumers, see Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Chemosphere
