Green Right Now Reports

Autism now affects one in 88 kids, soaring in the last few decades, seemingly out of nowhere, to become a major health issue.

Early exposure to crop pesticides can degrade cognitive ability, some studies show. (Photo: Aqua Mechanical)

Research shows that genetics plays a role in autism, but many scientists believe that environmental factors are as important in triggering the disorder. They continue to search for the cause or causes behind the explosion of autism.

A recent workshop at Mount Sinai Children’s Environmental Health Center focused on the 10 chemicals and heavy metals that many scientists strongly suspect could be among autism’s environmental triggers. (Autism was a co-sponsor of the workshop.)

Three researchers studying autism causes at Mount Sinai surveyed the scientific literature and singled out these compounds or classes of chemicals as potential culprits because leading researchers have found that they interfere with the prenatal and early development of children’s brains.

These pollutants, with links to the original research, include:

  • Lead (Jusko et al. 2008) Once found in house paint and gasoline, lead still turns up  in consumer products and even kids’ toys and jewelry. It’s been found to impair cognitive ability in children who’ve been exposed.
  • Methylmercury (Oken et al. 2008) Methylmercury is what mercury emitted into the air from coal plants is converted into in aquatic environments. Once in seafood, it is “biomagnified” as it moves up the food chain, becoming more potent. That’s why pregnant women and children should only eat limited amounts of tuna in a given week. It’s also been associated with cognition and behavioral issues.
  • Polychlorinated biphenyls or PCBs (Winneke 2011) These were once used in circuit boards, and a variety of products like coolants. They persist in the environment, leading to human exposure from food, soil and air. Neonatal or early exposure can contribute to lower IQs and Attention Deficit Disorder, according to a wide number of studies.
  • Organophosphate pesticides (Eskenazi et al. 2007; London et al. 2012) Both organophosphate and organochlorine pesticides are used in agriculture, meaning they arrive at your doorstep as food residues and also end up in rivers, lakes and soil. These pesticides have been found to child development, including neurological development.
  • Endocrine disruptors (Braun et al. 2011; Miodovnik et al. 2011) BPA, used to make polycarbonate plastic and canned food resin liners, is just one example of a known endocrine disruptor that turns up in every day products. Many other chemicals are believed to act as endocrine disruptors even in small amounts. The Braun study cited here found more anxiety and poorer emotional control among young children with the highest BPA exposure. Endocrine disruptors also have been found to negatively impact reproductive development.
  • Automotive exhaust (Volk et al. 2011) Tailpipe air pollution has been linked to increased risk of lung ailments and neurologic conditions, like autism.
  • Polycyclic aromatic hydrocarbons or PAHs (Perera et al. 2009) These carcinogenic compounds are found in grilled meat, petroleum products and emissions from fossil fuels.
  • Brominated flame retardants (Herbstman et al. 2010) These were once nearly ubiquitous in cushions in upholstered furniture, hence, the new methods of making furniture, mattresses from cotton, wool and soy products. California still has a strict flame retardant requirement causing many manufacturers to continue their use. Even firefighters now say that the toxic fumes released by flame retardants during a house fire present an obvious danger.

These studies and others show that chemicals in the environment can injure the developing human brain by altering DNA structure and gene expression. The chemicals interfere at critical growth junctures, suppressing or exposing certain genetic coding.

The three Mt. Sinai scientists who assembled this “short list” of chemicals implicated in autism, Philip J. Landrigan, Luca Lambertini and Linda Birnbaum, acknowledge that the “significance of early chemical exposures for children’s health is not yet fully understood.”

But they see that not as a reason to doubt the potential environmental causes of autism, but as a warning, as human activities continue to churn out more synthetic chemicals.

“The U.S. Environmental Protection Agency has identified 3,000 “high production volume” (HPV) chemicals that are in widest use and thus pose greatest potential for human exposure (Goldman 1998). These HPV chemicals are used today in millions of consumer products. Children and pregnant women are exposed extensively to them, and CDC surveys detect quantifiable levels of nearly 200 HPV chemicals in the bodies of virtually all Americans, including pregnant women (Woodruff et al. 2011),” the authors write in the article about their survey, A Research Strategy to Discover the Environmental Causes of Autism and Neurodevelopmental Disabilities, published in Environmental Health Perspectives.

Landrigan, the Ethel H. Wise Professor of Preventive Medicine, is a pediatrician and epidemiologist, who has published more than 500 scientific papers and five books. His studies on low-level lead exposure in children contributed to the government’s decision to remove gasoline from lead and paint in the 1970s.

Luca Lambertini, a molecular biologist and assistant professor of preventive medicine at the Mount Sinai School of Medicine, received his PhD from the University of Bologna in 1995. His research focuses on genomic imprinting, long non-protein-coding RNAs, and mitochondrial DNA methylation,  including studying placental tissue to investigate genomic imprinting.

Linda S. Birnbaum, director of the National Institutes of Environmental Health and Science (NIEHS), and the NTP, oversees a budget that funds multidisciplinary biomedical research programs and prevention and intervention efforts that encompass training, education, technology transfer, and community outreach. She has a PhD from the University of Illinois in microbiology and is a board certified toxicologist, formerly with the EPA.