Air sampling in the Monongahela Valley by local environmentalists has revealed high levels of some toxic chemicals and prompted the Allegheny County Health Department to add a new air monitoring site in Elizabeth.

Results of the sampling by Residents for a Clean and Healthy Mon Valley and Clean Water Action, to be announced at a workshop this morning in Jefferson Hills, showed high levels of benzene, acrylonitrile and five other toxic chemicals at sites in Elizabeth, West Elizabeth and Clairton.

Though these and other chemicals are known to be toxic to humans, their health effects as air pollutants are not well understood and they are not routinely regulated by environmental agencies.

The seven chemicals highlighted by local testing were at levels in excess of Environmental Protection Agency guidelines or above standards set in Texas or North Carolina, said Suzie Brindle, program organizer for Clean Water Action.

The sampling technique used by the groups provides only a snapshot of what's in the air, cautioned Darrell Stern, section head for air monitoring at the health department. But the findings persuaded the department to add a monitor for toxic chemicals in Elizabeth that should provide more scientific results, he said.

The groups used a simple technique called "bucket sampling," in which a vacuum cleaner is used to draw air into a plastic bag inside a sealed bucket.

Though this type of sampling has limitations, similar work near Neville Island two years ago prompted the county to launch a $1.6 million study of toxic air pollutants around the industrial island. That study, funded by the county Clean Air Fund and the EPA, is just about to get under way.

In contrast to the sample buckets, which fill up in about a minute, the new monitor in Elizabeth will continuously monitor the air and provide 24-hour averages that are more representative of air pollution conditions, Mr. Stern said. The monitor will be in addition to an existing benzene monitor at South Allegheny High School, downwind of U.S. Steel's Clairton Coke Works.

"We're kind of doing this on the fly," Mr. Stern said, noting that the yearlong Neville Island study will take up most of the time of the health department's air monitoring staff.

The Neville Island study, which is being done in conjunction with Carnegie Mellon University, will use mobile and stationary monitors to sample toxic air pollutants in and around the island. They also will monitor air Downtown to gauge the contributions of motor vehicle exhaust and sample the air in South Fayette to determine what chemicals come from upwind of the county.

The Mon Valley sampling will be discussed at a workshop and health fair from 9 a.m. to 1 p.m. today at Jefferson Hills Elementary School, 875 Old Clairton Road, Jefferson Hills. Participating will be representatives from the health department, the University of Pittsburgh Graduate School of Public Health, the American Lung Association and the Neville Island Good Neighbor Committee.