Environment Maryland Research and Policy Center
The concentrations of toxic chemicals in Maryland’s air pose a serious health threat. These hazardous substances, known as air toxics, come mostly from cars, trucks, and other motor vehicles.
Marylanders exposed to air toxics can suffer from a variety of illnesses, including cancer, birth defects, neurological damage, and respiratory problems such as asthma. While scores of harmful air toxics exist, a few of the chemicals, including acetaldehyde, 1,3-butadiene, and benzene, are responsible for most of the health risk.
According to data from the federal Environmental Protection Agency (EPA), residents of every Maryland county faced an excessive risk of cancer—greater than one case for every million residents— from exposure to air toxics in 1999 (the most recent year for which data is available). Cars and trucks were leading contributors to those excessive risks.
• Marylanders were exposed to levels of benzene an average of 11.3 times higher than EPA’s standard for the health risk from cancer. Residents of every county in Maryland were exposed to benzene levels above EPA’s cancer risk threshold, with residents of Baltimore City exposed to benzene levels more than 20 times the cancer risk threshold.
• Average exposure to levels of 1,3- butadiene was 4.1 times as large as EPA’s guideline in Maryland. Exposure exceeded the cancer risk threshold in more than half of Maryland’s counties.
• Marylanders’ exposure to acetaldehyde averaged 3.4 times the cancer risk threshold. Airborne acetaldehyde exceeded the guideline in every Maryland county.
• All air toxics combined were present at levels averaging 40 times the health-protective threshold across Maryland. The factor by which exposure exceeded the cancer risk threshold ranged between 11.3 and 62.1 throughout the state’s counties.
This data does not include the serious non-cancer health effects associated with the pollutants and understates their full health impacts as a result. Cars, trucks, and other mobile sources were responsible for:
• 84 percent of Maryland’s benzene emissions.
• 99 percent of Maryland’s 1,3-butadiene emissions.
• 87 percent of Maryland’s acetaldehyde emissions.
Maryland can reduce citizens’ exposure to air toxics and the accompanying health risks from mobile sources by adopting air pollution standards that are more protective of public health.
As a strong first step, the Maryland Department of the Environment should immediately adopt the Clean Cars Program to reduce toxic emissions from cars and trucks. A 2005 Maryland PIRG Foundation study found that the Clean Cars Program would reduce emissions of air toxics from light-duty vehicles by approximately 12 to 15 percent within 20 years compared with projected emission levels, under weaker federal air pollution standards. On a pollutant by pollutant level, the Clean Cars Program reduces air toxics emissions by 57 to 79 percent versus today’s pollution levels. Those emission reductions would be the equivalent of taking approximately 190,000 of today’s cars off the state’s roads.