The Clean Air Act classifies 188 chemicals as Hazardous Air Pollutants or toxins. These chemicals can damage human and animal genetics, cause reproductive effects such as birth defects or damage to liver and kidneys. Many of these chemicals can cause cancers.

Some toxic chemicals can remain in the environment for decades, even centuries before breaking down. These long-term, persistent air pollutants can build-up or bioaccummulate in the food chain. Many states have concerns about the levels of mercury in fish and other animals. Over 32 states issue advisories for children and nursing and pregnant women to limit fish consumption. Much of this mercury first enters the environment as air emissions.

The U.S. EPA estimates 23 toxic chemicals are in high enough concentration in Iowa's air to pose excessive health risks from long-term, low-level exposure. EPA predicts some health concerns in Iowa are attributed to breathing these chemicals for many years.

Despite toxic chemical reductions being a major goal in the 1990 Clean Air Act, Iowa is one of 14 states without an air toxics control program. Currently Iowa's air is monitored for six common pollutants (sulfur and nitrogen oxides, carbon monoxide, particulates and ozone smog) and limited monitoring in five urban areas for toxic chemicals has just begun.

Without rules and resources to address toxic emissions fully, permits often do not specifically restrict toxic exposures, although this occurs for sulfur and nitrogen oxides, particulates, and carbon monoxide. Some toxic controls are specifically targeted under the Clean Air Act, affecting some emission sources, but not impacting others. Vehicle exhaust, trucks, buses, and other mobile sources are responsible for a significant portion of toxins in Iowa's air. Estimates place this figure at roughly 50 percent.

The DNR strongly believes a toxics control program is needed. However, this requires state and public support for adequate funding and staffing before a viable control program can begin.

Toxics of Special Concern in Iowa:

• Acetaldehyde
• Acrylonitrile
• Aresenic and compounds
• Benzene
• Butadiene (1,3)
• Cadmium and Compounds
• Carbon Tetrachloride
• Dioxane (1,4)
• Ethylene Dibromide
• Ethylene Dichloride
• Formaldehyde
• Methyl Chloride
• Methylene Chloride
• Nickel and compounds
• Nitropropane
• P-Dichlorobenzene
• Polychlorinated biphenols (PCB)
• Tetrachloroethylene
• Trichloroethylene
• Vinyl Chloride