Preliminary tests of air outside Chicora School of Communications in North Charleston identified several toxic chemicals, including one that in a more potent form was used as a chemical weapon in World War I.

The Environmental Protection Agency is monitoring air outside 63 schools in 22 states to find out whether children are being exposed to dangerous levels of toxic chemicals on a regular basis. Chicora is the only school in South Carolina being tested.

In a news release Thursday describing its preliminary findings, the EPA said it found low levels of acrolein, benzene, chromium, manganese and several other chemicals in the air. None of the samples showed levels that present an immediate danger.

However, levels of acrolein were in a range that EPA officials said merit further study. Acrolein is a pollutant that can irritate people's eyes, nose and throats. People with asthma and allergies are particularly sensitive to the chemical. It comes from industries, trucks, boats and other sources, and in higher concentrations, it was used as a chemical weapon in World War I.

The EPA found levels outside the school ranging from 2.5 to 3.5 micrograms per cubic meter of air. The EPA considers 7 micrograms a danger when people are exposed for just a short period. At levels between 7 micrograms and .02 micrograms, people might see effects if they're exposed to the chemical for long periods, said Dawn Harris-Young, an EPA spokesman in Atlanta.

"We're trying to get a better handle on the concentrations and what those health effects might be," she said. The EPA said in several statements that the results shouldn't prompt parents to switch schools, or keep children indoors. Indoor levels of air pollutants often are the same as outdoor levels.

The EPA began testing schools after a USA Today investigation last year found air outside hundreds of schools in South Carolina and elsewhere with high levels of toxic chemicals. Dubbed "The Smokestack Effect," the newspaper's report gave particularly bad air pollution grades to Chicora School of Communications (formerly Chicora Elementary), Mary Ford Elementary, Charlestowne Academy, Academic Magnet High and North Charleston High.

Only 168 schools out of more than 120,000 had worse air than what's outside Chicora, the newspaper found. It said the two most prevalent pollutants near the North Charleston schools were manganese, which can cause mental disturbances and physical problems, and chromium compounds, which can cause numerous health issues.

Chicora is in a low-income neighborhood near the old Navy base. The EPA selected the school for monitoring because it's in an urban area with emissions from a mix of large and small industries, vehicles and other sources.

The USA Today series mostly used data and computer models to identify schools with high levels of toxic chemicals.

The EPA's preliminary results released Thursday validated those results and residents' concerns about air pollution, said Nancy Vinson of the Coastal Conservation League, an environmental group that's challenging the State Ports Authority's plan to build a new container terminal in the area.

She said that unless the ports authority takes steps to reduce pollution, the terminal would only add to the area's already intolerable air pollution situation. "We can have a green port," she said.

"Safety is the Charleston County District's highest priority," said Susan Smyre Haire, the district's communications officer, adding that school leaders are working closely with state environmental officials and industry representatives on the air-pollution issue.