That's nearly 25 percent of the area's population, an exposure level higher than the metropolitan areas of Columbus and Akron, where one-fifth in each city live in diesel "hot spots."

"Diesel exhaust is putting too many people at risk," said Staci Putney McLennan, clean-air program director for the Ohio Environmental Council, a Columbus-based advocacy group that issued the report.

Cincinnati's exposure level tops those of Columbus and Akron because the Queen City has a higher density of people living near heavily traveled roads and highways, McLennan said.

Studies of Dayton, Cleveland and Toledo are expected to be released in 2005.

The environmental group singles out diesel emissions as a major obstacle to Ohio cities complying with new federal clean air standards for particulate matter and for ground-level ozone. States have three years to draw up a plan to ensure their counties come into compliance by 2010.

Failure to meet the standards could mean the loss of federal funding or fines for dirty air.

Here are Greater Cincinnati's "dirty dozen" (neighborhoods that have the highest percentage of people living in diesel hot spots):

• Ohio: Arlington Heights, Butlerville, Cheviot, Kenwood, Ross, Mariemont, Olde West Chester and Springdale.

• Kentucky: Crestview Hills, Lakeside Park, Park Hills and Walton.

The environmental group counted the number of people in the 10-county area who live within a quarter-mile of a roadway with diesel soot levels of at least 675 grams per mile per day.

McLennan advises people living in these areas to urge their school districts and governments to adopt "anti-idling" polices and to minimize the time that children spend outside when school buses are arriving or departing, or when buses are parked at bus stops.

Beyond that, advocates urge Ohio and Kentucky lawmakers to create pools of money that would help schools and transit systems retrofit existing diesel bus fleets with emission controls, replace worn-out vehicles with new ones that have clean-burning technology or switch to alternative fuels, such as bio-diesel, which is made with soybean oil and gives a 20 percent cleaner burn.

Representatives from the diesel industry faulted the study, saying it minimizes the efforts that they have made to reduce emissions.

"The diesel industry supports the kind of recommendations made here, and we've been calling governments to make funding available for the cleanest technology available," said Allen Schaeffer, executive director of the Diesel Technology Forum in Washington, an organization of diesel engine manufacturers, fuel suppliers and exhaust-treatment manufacturers.

Such programs are under way, said Ken Edgell, an administrative coordinator with Hamilton County's Department of Environmental Services. But money is an issue.

Devices that clean diesel exhaust cost $2,000 to $5,000 each, and bio-diesel costs about 25 cents per gallon more than diesel.

Diesel dangers

Diesel exhaust contains tiny particles of unburned formaldehyde, benzene, sulfur and various metals. Studies have linked diesel emissions to cancer; asthma; irritation of the eyes, nose and throat; and inflammation of the lungs. Studies of note:

• A study in Denver identified that children living within 250 yards of urban roadways with heavy truck traffic were six times more likely to develop cancer and eight times more likely to develop leukemia.

• A study in Erie County, N.Y., found that children living within 200 meters of roadways with heavy truck traffic had a significant increase in risk of asthma hospitalization.

Source: Ohio Environmental Council

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E-mail mleingang@enquirer.com