Emerging Research Finds Air Pollution Contributes to Development of Autism, ADHD

Fossil fuel emissions do not only contribute to climate change, they can also have direct adverse effects on human health. While the cardio-vascular risks of air pollution exposure have been understood for some time, there is a growing understanding of the role particulate matter (PM) plays in a variety of developmental disorders. Several recent studies (see below) suggest that living, working or going to school close to major roadways exposes individuals to levels of particulate matter that make them more likely to suffer from a whole host of developmental and neurological disorders, including Autism Spectrum Disorders (autism), Attention Deficit Hyperactivity Disorder (ADHD) and general declines in cognitive functioning. Scientists are unsure about how PM contributes to autism and other developmental disorders, but they do know that contaminants carried into bodies by PM can penetrate into cells and alter neurological functions.

Particulate matter is a term applied to the complex mixture of solid and liquid particles found in the air. The Environmental Protection Agency (EPA) classifies particulate matter as particles with a diameter measuring between 2.5 and 10 micrometers. For scale, 10 micrometers is 30 times smaller than the width of a human hair. Ultra-fine particulates are those measuring 100 nanometers or less. While such particles occur naturally—from water, volcanoes, salts, soil, and other sources—the main source of particulate matter in urban areas is combustion, including that of fossil fuels such as gasoline and diesel as well as coal and wood. The smaller the particulates are, the greater their potential is to adversely affect human health. The smallest particles, PM_2.5 and ultra-fine particulates, pose the greatest danger. Their small size allows them to enter the lungs and, worse, the bloodstream. Risk factors for PM exposure include living near a freeway, construction site, or power plant. As the world becomes more urbanized, the health risks of air toxic exposure will continue to grow.

The risk of developing autism-spectrum disorders disproportionately affects the young, especially those in utero. A child is particularly at risk for developing neurological disorders if its mother is exposed to significant amounts of PM, especially PM_2.5, during her pregnancy. For example, one study found that a child’s risk of autism doubles if its mother lives near a freeway in her third trimester. The incidence of autism in children has rapidly increased over the past decade, rising from one in 150 children in the year 2000 to one in 68 in the year 2010. While genetics play a role in autism risks, scientists are wondering what environmental factors may be driving this troubling upward trend.

It is unclear whether current and pending federal regulations on vehicle emissions and other sources of air pollutants will be enough to address these growing environmental health risks. The last federal regulatory action on PM_2.5 was in 2012, when the EPA, under court order, tightened its standards and mandated that U.S. counties keep daily levels of PM_2.5 below 12 micrograms per cubic meter by 2020. But what is clear is that burning fossil fuels not only pollutes our air and water, raises sea levels, and increases global temperatures, it also creates toxics that affect child development and interact with genes in complex ways that we don’t yet fully understand.

Author: Rachael Shook