The Missing Link: DDT, PCBs, and Autism Spectrum

The Missing Link: DDT, PCBs, and Autism Spectrum

In the early 1800s, Edward Jenner began experimenting with strains of a disease then-referred to as “cowpox” with the goal of showcasing a possibility to protect children from smallpox by injecting the child with a lymph from a cowpox blister. Jenner’s science was met with staunch opposition from critics arguing “sanitary, religious, scientific, and political” reasons to counter Jenner’s research in England and the United States. This criticism is undoubtedly the reason why the 1853 Vaccination Act, and an addendum to this act in 1867 requiring mandatory vaccinations of children up to 14 years of age, were met with such opposition including marches and demonstrations against vaccination practices, leading to the 1898 Vaccination Act removing penalties for parents who conscientiously did not wish to vaccinate their children, for one reason or another.

 

An outbreak of smallpox in 1902 Massachusetts saw increased pro- and anti- vaccination movements, including a US Supreme Court ruling that states could enforce compulsory measures to protect public health in the event of a transferable disease. Anti-vaccination movements saw bursts of traction again in England in the United States throughout the 1970s and 1980s. In 1998, British doctor Andrew Wakefield, along with a number of his colleagues, published a paper in The Lancet citing possible evidence of coordination between bowel disease and autism linked to the MMR (Measles, Mumps, and Rubella) vaccine. Despite the small sample size of Wakefield’s research (n=12) and the Lancet pulling the paper from their archive in 2010, Wakefield being found guilty of ethical violations including fraudulent data for the sake of financial gain, and admitting that elements of the published paper were incorrect, Wakefield’s paper found its way into the spotlight in the 2010s in American popular culture when celebrity Jenny McCarthy began advocating for the anti-vaccine movement, citing Wakefield’s paper as evidence that the MMR vaccine has potential to afflict infants with autism.

Since McCarthy came public with her anti-vaccine (dubbed “anti-unsafe-vaccine” by her advocacy group Generation Rescue) movement, the American public has seen a resurgence of anti-vaccination movements across the country – again citing Wakefield’s paper and McCarthy’s organization as evidence that vaccines have the potential to cause autism in infants and young children. McCarthy’s efforts spearheaded a contemporary review of medical research into vaccines and the vaccination process, hoping to once again prove or debunk the theory of links between vaccination and autism rates in children.

 

What researches in the US found in conjunction with medical researchers in Finland and Europe, was that while it may not necessarily be vaccines themselves causing autism in children, it may be likely that certain vaccines act as a “trigger” – along with other predisposing genetic health factors – for autism

Dr. Alan Brown at Columbia University Medical Center in New York City, NY partnered his research with medical professionals in Finland to gather a sample size of 1,000,000 pregnancies, 778 of which birthed children diagnosed with autism who were born between 1987 and 2005. Brown chose Finland because the Scandinavian country possesses a universal health care system and tracks medical diagnoses in all of its citizens. This made it easier for researchers in Finland and the US to analyze blood samples taken from the children’s mothers while they were pregnant. What Brown and the researchers found was shocking: mothers who possessed higher levels of the pesticide chemical known as DDE (what the human body metabolizes DDT into) during early stages of pregnancy were more likely to give birth to children who would develop autism – 32% more likely, to be precise. Women with increased levels of DDE found in their blood during early pregnancy showed they were more than 60% more likely to give birth to a child with both autism and an intellectual disability. Brown’s report, published in August of 2018 to LiveScience, says that Brown and the researchers also accounted for several other control factors, including “the age of the mother, the mother’s socioeconomic status and whether the parents had a history of psychiatric disorders.” Researchers also tested for PCBs in blood samples but were unable to deduce a link between PCBs and autism in the study sample size.

“DDT is very long-lived in the body, so a woman with high levels may not be able to do much about it at the time she starts thinking of getting pregnant,” said Marc Weisskopf. Weisskopf, who was not involved in the study, is a professor of environmental epidemiology and physiology at the Harvard T.H. Chan School of Public Health. “For any individual mother, I would still stress that the absolute increase in risk from such exposure still certainly remains small. From a larger societal point of view, it is more evidence to try and limit DDT exposures overall.”

 

It’s at this point in the blog post where we have to recommend you take a minute to reread our post from earlier this year on the chemical similarities between PCBs, DDT, PAHs, and dioxins which can be found: here.

 

From a chemical standpoint, PCB, dioxin, and DDT molecules are all equally persistent (i.e., do not naturally break down or deteriorate) which allows them to exist in natural environments – or organisms – indefinitely, and both series of chemicals accumulate and magnify as they work their way up the food chain. Eventually, the biomagnified mass of PCBs or DDT can eventually be passed down from mother to infant, effectively transferring the accumulated load of chlorinated toxins to the newborn most commonly through breast milk of the nursing mother. A more detailed explanation of this process can be found in the short film, PCBs: An Immoral Poison.

While none of this is good news, it does help shed a bright light on a whole series of questions our society has been asking regarding the known causes – if any – of autism spectrum in children. Since the release of Rachel Carson’s Silent Spring in 1962, light has been shed on the harmful effects spraying DDT-based pesticides and insecticides, and because DDT is persistent and does not naturally break down, even trace remnants of DDT sprayed decades ago to kill mosquitoes and bugs for the preservation of fruits, vegetables, and other crops found its way into our soil and groundwater. Unfortunately, this means that virtually everyone alive today possesses some level of DDT in their body, as is the case with PCBs; however, because DDT and PCBs biomagnify after ingestion and accumulate, young children and new generations are at the highest risk of exposure since they inadvertently receive a higher-magnified dose of the chlorinated toxins prior to birth. This exposure of a higher dose of DDT, metabolized as DDE, is transferred to the fetal brain through the mother’s placenta.

 

Even though this study only sheds light on one aspect of a link between the development of autism spectrum in children and maternal exposure to DDT, it cannot definitively be determined as the sole cause of autism. Various past studies on children with autism and their parents have also shown factors such as lower birth rates and older parents can also show a link to autism spectrum in children. Undoubtedly, much more scientific research remains to be done before we can fully understand the causes of autism spectrum development in children.

One thing is certain: Dr. Brown’s study further confirms the dangers of human exposure to chlorinated environmental toxins such as DDT and PCBs, and solidifies the dangerous side effects of this exposure which often include intellectual development disorders in young – and unborn –  children.

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SMWG Fall Sponsor Forum Oct. 3-5, 2019

Clean Gulf 2018 Nov. 12-15, 2018

Battelle Sediments Conference Feb. 11-14, 2019

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