Americans living in most urban areas have a greater than 25-in-a-million chance of developing cancer from air toxics, and the remainder of the population has a less than 25-in-a-million chance.

Those were some of the conclusions contained in the EPA´s second National Scale Air Toxics Assessment released Feb. 22. The information is intended as a tool to guide local, state and federal officials in developing steps to reduce toxic air pollution.

While the disparity in risks seems large, EPA officials tried to put the risks into perspective by saying that when all risk factors are taken into account, Americans have about a one-in-three chance of developing cancer during their lifetimes.

"Since 1990, we´ve significantly cut toxic emissions and risks in the United States," said Bill Wehrum, acting EPA assistant administrator for air and radiation. "This tool will help EPA and states refine our understanding and approaches to further reduce air toxics."

Since the Clean Air Act was amended in 1990, the United States has made significant progress in reducing air toxics from industry, fuels and vehicles, according to the EPA. New standards are projected to reduce annual emissions of air toxics by about 1.7 million tons from 1990 levels when fully implemented, according to the EPA.

In addition, current statistics could prove better than the estimates in the recent EPA assessment because the agency used air quality data from 1999.

The EPA plans to develop new national scale assessments as inventory data from subsequent years become available. The next analysis will focus on exposure and risks from 2002 emissions, according to the agency.