Air Toxics Hot Spots

Two articles published in 2005 in the Journal of Epidemiology and Community Health explored the possible relationships between emissions from the combustion of petroleum and increased risks of childhood cancers. The outcomes from these studies was that significantly higher relative risks were observed with birth proximity within 1 km of emissions hotspots of carbon monoxide, PM10, volatile organic compounds, particularly benzene and 1,3-butadiene, oxides of nitrogen, dioxins and benzo(a)pyrene. The study compared the relative risks between two groups – the first being children born within 1 km of significant emissions sources who remained in proximity to those sources, and the second being children born within 1 km of the emissions sources, but who’s families had migrated away from those sources. The timeframe examined was between 1966 and 1980.

Emissions of 1,3-butadiene and carbon monoxide, from mobile source emissions were particularly strong predictors of increased childhood cancer risks. Emissions sources where proximity and increased childhood cancer risks were related included bus stations, hospitals, trucking terminals, railways and oil installations.

The epidemiological studies in the literature don’t uniformly show increased risks with proximity to emission sources, but there is some replication (one of those studies was posted here last year). One interesting source of amplification for these results is the Multiple Air Toxics Exposure Study, published in 2000 by the South Coast Air Quality Management District (SCAQMD) in California.

That study concluded that the lifetime cancer risk in the Basin is about 1,400 per million people (note: USEPA uses a risk range from 1 per million to 100 per million as risk management thresholds for regulating cancer risks from hazardous air pollutants). Emissions from mobile sources (e.g., cars, trucks, trains, ships, aircraft, etc.) represent the greatest contributor. About 70% of all risk is attributed to diesel particulate emissions; about 20% to other toxics associated with mobile sources (including benzene, butadiene, and formaldehyde); about 10% of all risk is attributed to stationary sources (which include industries and other certain businesses such as dry cleaners and chrome plating operations). An overview of assessing the health risks from toxic or hazardous air pollutants can be found here.

So, beyond kicking our dependency on foreign sources of petroleum and controlling greenhouse gas emissions, there appears to be a potential public health benefit associated with reducing our reliance on motor vehicles.