Measure E4: Hazardous Air Pollutants and Health Benchmarks

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• In 1999, almost all (99.8 percent) children lived in counties in which the combined estimated concentrations of hazardous air pollutant exceeded the 1-in-100,000 cancer risk benchmark.
• About eight percent of children lived in counties in which hazardous air pollutants combined to exceed the 1-in-10,000 cancer risk benchmark. The pollutants that contributed most to this result were chromium VI compounds, benzene, coke oven emissions, and hydrazine. Chromium VI, benzene, and coke oven emissions are considered by EPA to be “known human carcinogens” and hydrazine is a “probable human carcinogen." 
• Approximately 89 percent of children lived in counties in which at least one hazardous air pollutant exceeded the benchmark for health effects other than cancer. In almost all cases, this result was attributable to the pollutant acrolein, which is a respiratory irritant. More than 75 percent of acrolein emissions are from mobile sources such as cars, trucks, buses, planes, and construction equipment.
• Exposures to diesel particulate matter are not included in this measure, because of uncertainty regarding the appropriate values to use as cancer benchmarks. Some studies have found that cancer risks from diesel particulate matter exceed those of the hazardous air pollutants considered in this measure.¹ Although EPA does not endorse any particular cancer benchmark value for diesel particulate matter, if the State of California’s benchmark for diesel particulate matter were used in this analysis, 95 percent of children would live in counties where hazardous air pollutant estimates combined to exceed the 1-in-10,000 cancer risk benchmark.

Healthy People 2010:

Objective 8-04 of Healthy People 2010 focuses on reducing emissions of hazardous air pollutants.

1. South Coast Air Quality Management District. 1999. Multiple Air Toxics Exposure Study II. http://www.aqmd.gov/matesiidf/matestoc.htm.