Bad Air Hikes Risk of Cancer in Some Areas

Concentrations of toxic air contaminants are “significantly higher” in the Rancho Dominguez, Burbank and Hawthorne areas than other sites tested in the South Coast Air Basin and pose cancer risks that, while still low, are twice as high as elsewhere, a study by the region’s air pollution control agency has found.

Under the worst-case projections, individuals living in those three areas run an increased risk of cancer of 0.1%. While the heightened risk is low in percentage terms, it nonetheless is many times greater than the risk normally deemed acceptable by government regulators in controlling emissions.

A 0.1% increased risk is 1,000 cancers in 1 million. But the South Coast Air Quality Management District routinely uses a one-in-100,000 risk as the maximum acceptable in permitting new sources of air pollution emissions. The risks are based on the assumption that an individual will be exposed to those concentrations over a 70-year lifetime.

The report, scheduled to be delivered to the AQMD governing board on Friday, marks the first time that the air pollution control agency has attempted to pinpoint areas within the air basin where cancer risks from multiple toxic air contaminants are highest. In June, 1987, the district outlined the toxic air contaminant problem but focused on which contaminants posed the greatest risk.

“There is potential for some regions within the basin to experience long-term average concentrations of toxics which are significantly higher than basin-wide averages,” the study said. “These regions of elevated concentrations, or hot spots, are of concern because they represent areas where the public is at greatest risk from long-term, low-level exposure to toxic air contaminants.”

The AQMD cautioned that its risk estimates in some ways may understate the actual risks because the health effects of some of the pollutants are unknown, and because the risk estimates do not take into account indoor exposures. On the other hand, errors in the sampling and analysis may tend to overestimate the risks.

The report is expected to become the basis for future rules on air toxics that are planned before the middle of 1989. One rule under study would allow the AQMD to require new toxic air emission limits on existing air pollution sources. The release of the findings followed two evacuations involving up to 27,000 people in Montebello and adjacent Eastside communities over the Labor Day weekend after toxic chlorine gas escaped from the Grow Group Inc. plant in Commerce.

But, unlike the sudden accidental release of chlorine over the weekend, the 20 toxic pollutants measured by the AQMD in a three-year, $385,000 study are routinely spewed into the atmosphere every day. Because these pollutants defuse readily, there are usually no acute health effects except to sensitive people. But the health effects, if any, of long-term exposure to relatively low levels of the pollutants are poorly understood. It is known that concentrations of most of the contaminants studied are higher in the winter than in summer because of meteorological conditions.

Using well-established risk calculations and applying them to the concentrations of toxic air contaminants at monitoring stations, the AQMD was able to calculate the potential cancer risks in various locations within the South Coast Air Basin, which includes Los Angeles, Orange, San Bernardino and Riverside counties.

In the eastern Los Angeles area, including East Los Angeles, Bell Gardens and Maywood, the increased cancer risk of the combined impact of the mixture of air contaminants was 902 in 1 million. The estimated risk in the South Coastal region, including Rancho Dominguez and Long Beach, is 1,086 in 1 million. And in the Burbank area, the risk was calculated at 1,143 in 1 million. The risk was 868 in 1 million in the southwest coastal areas of Hawthorne and Gardena.

Toxic contaminants in those areas were approximately twice as high as levels found in the far inland valleys and Orange County. By comparison, the risk in Orange County (Irvine, Anaheim and Yorba Linda monitoring stations) was pegged at 614 in 1 million, and 594 in 1 million in the Upland and Rubidoux areas. It was 661 in 1 million in the Azusa and El Monte areas.

The 20 pollutants, monitored at 19 sites, consisted of seven metals and 13 organic gases. Eleven of the 20 are known carcinogens. The metals are arsenic, beryllium, cadmium, chromium, lead, mercury and nickel. The organic gases are benzene, carbon tetrachloride, chloroform, ethylene dibromide, ethylene dichloride, methyl bromide, methylene chloride, perchloroethylene, toluene, 1,1,1,-trichloroethane, trichloroethylene, vinyl chloride and xylenes.

The highest concentrations of all the metals were found at the Rancho Dominguez site, which the report noted is located in an industrial zone where there are major oil refineries and which is downwind of most of the major emission sources within the South Coast Air Basin.