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U.S. study finds high levels of poisons in city air

Source: Twin Cities Star Tribune,

U.S. study finds high levels of poisons in city air

Tom Meersman / Star Tribune

A first-of-its-kind federal study indicates that metropolitan areas across the United States, including the Twin Cities, contain high levels of hazardous contaminants in their outdoor air.

Conducted by the Environmental Protection Agency (EPA) and known as the Cumulative Exposure Project, the soon-to-be-released study is a first attempt to quantify the soup of chemicals that exists in air throughout the country.

The report does not address health concerns from the exposures. But other work published in scientific journals earlier this year indicates that the EPA's findings exceed "benchmark" levels for cancer in many cases and constitute a potentially significant national public health concern.

Minnesota officials say the estimates don't pose an immediate health emergency. But they have been analyzing the federal data for a couple of weeks and have determined that eight chemicals -- seven of which are carcinogens -- are present in the outdoor air at levels above state health guidelines.

"It gives us concern that the air we're breathing, especially in the metro area, is not healthy," said Greg Pratt, an air-toxics specialist for the Minnesota Pollution Control Agency (MPCA).

The EPA study goes beyond previous efforts that focused on regulating a handful of chemicals in ambient air and studies of other chemicals that were limited in scope and geography.

The new study uses 1990 nationwide emissions data from vehicles, factories, incinerators, household furnaces and other sources. It combines that data in a computer model using meteorological patterns to simulate where air pollutants go.

The result is a coast-to-coast snapshot of pollutants, featuring average outdoor concentrations for 148 contaminants in each of the 60,803 census tracts in the contiguous United States.

Census tracts vary in physical size, but each typically has 4,000 to 5,000 residents. The EPA data were compiled months ago and have been shared with pollution and health officials, in part to prepare them for questions from the public.

Minnesota officials took the EPA estimates and compared them with state health guidelines proposed for the chemicals. They found that about 45 percent of the state's 1,230 census tracts -- most in the seven-county Twin Cities area -- had six or seven air pollutants that exceeded state guidelines for long-term exposure. They include benzene, formaldehyde, carbon tetrachloride, nickel, arsenic, chromium, 1,3-butadiene and acrolein.

Four chemicals evaporate from gasoline or are byproducts of combustion. MPCA officials estimate that about half of the health risks from all air toxics in the study comes from cars, trucks and other vehicles. Three of the other chemicals are metals.

MPCA Commissioner Peder Larson said data should prompt discussion about such issues as "limiting urban sprawl, promoting alternative forms of transportation, introducing cleaner fuels and encouraging telecommuting.

"Our lifestyle choices have made us part of the problem. Now we're going to have to learn how to be part of the answer."

Pratt said the MPCA has confidence in the federal estimates, some of which are close to state measurements in small portions of the metro area. Pratt said the EPA may have overestimated the emissions of chromium and arsenic from taconite mines in northeastern Minnesota, however, and that those areas need further investigation.

State health officials also agree that the federal data are worthy of additional study.

"It underscores something that we've known for a long time, which is that there are concentrations of airborne pollutants in Minnesota and elsewhere that could pose a long-term health concern," said Larry Gust, health-risk assessment supervisor with the state Health Department.

Gust said that the EPA's estimates do not pose any "immediate health emergency." He also cautioned against reading too much into the data.

Another limitation of the study is that the EPA's estimates come from 1990 data, and the concentration of air toxics may have changed since then. Pollutants may have decreased if manufacturing plants shut down or changed their processes, or they may have increased in areas of increasing development.

Officials say it's difficult, if not impossible, to estimate how many cancers might be caused by exposure to pollutants. For some chemicals, little is known about cancer risks from exposures over a person's lifetime. For others, much is known about cancer risks but little about other effects, such as reproductive and developmental problems.

One discussion of the EPA data, published in the Environmental Health Perspectives scientific journal, indicated that for all the difficulties of estimating cancer rates, the estimates probably underestimate health risks.

For one thing, the averages computed for each census tract don't show temporary peak concentrations of pollutants, the article said. Analyses also tend to study hazards from individual pollutants rather than "additive or synergistic interactions" that could increase public health risks, it said.

The EPA also has made it clear that its data list only the potential hazards of breathing the chemicals. Future studies will examine exposures to chemicals contained in food and drinking water.

What's ahead

EPA authorities say they plan to refine their air-modeling techniques and will apply them next year to 1996 data. Federal officials took action several years ago to phase out one of the chemicals of concern -- carbon tetrachloride, which once was used widely as a solvent and in aerosol propellants and was shown to harm Earth's protective ozone layer.

But many of the other chemicals, especially those emitted by vehicles, are ubiquitous in urban areas and come from thousands of sources that would require a multifaceted effort to control.

Pratt said the MPCA will continue to measure pollutants through a monitoring network at six sites per year for five years. The agency also is planning to begin a cooperative study in March with the University of Minnesota and the University of Texas. It will place air-quality monitors on 75 citizen volunteers in three Twin Cities neighborhoods for several days each year.

Published Friday, December 11, 1998

State pollution data

Noah Musser / Star Tribune

see for maps that go with this

Minnesota pollution officials have analyzed federal data and found that average levels of eight hazardous air pollutants are above state health guidelines. The federal estimates are based on 1990 emissions data, so some numbers may not reflect current conditions. Some of the pollutants came from factories and mines, but most came from motor vehicles that are concentrated in urban areas.

What are hazardous air pollutants? A look at 8 key chemicals

Tom Meersman / Star Tribune

What are hazardous air pollutants? HAPS, also known as air toxics, are 188 chemicals that were defined as hazardous by 1990 amendments to the federal Clean Air Act. They include industrial chemicals, solvents, metals, pesticides and combustion byproducts.

Exposures to certain concentrations of HAPS can cause cancer or other serious health problems, such as birth defects, neurological damage and reproductive problems. Scientists know a lot about health effects from some HAPS, but very little about others. HAPS are emitted from such sources as factories, garbage incinerators, coatings applications, consumer products and vehicles.

HAPS should not be confused with six "criteria pollutants" that are regulated nationally, including lead, carbon monoxide, sulfur dioxide and ground-level ozone.

The Environmental Protection Agency has used computer models and 1990 emissions data to estimate the levels of 148 HAPS in every census tract in the country.

Minnesota experts analyzed the data and compared it with the state's proposed "health risk values," which are levels designed to protect human health.

The Minnesota Pollution Control Agency found that levels of eight HAPS exceed the guidelines:

Benzene: A major industrial chemical used to make gasoline and thousands of other products, including plastics, adhesives and pesticides. Emitted both through evaporation and from vehicle tailpipe emissions.

Carbon tetrachloride: Once used widely as a cleaning fluid and spot remover and produced in large quantities for refrigerants and propellants for aerosol cans. Production was phased out and eventually banned in the United States in 1996, largely because of its role in depleting Earth's ozone layer.

Nickel: A naturally occurring metal used to make steels and alloys, batteries, and in electroplating and ceramics industries. Released through mining and refining operations, garbage incineration and windblown dust.

Chromium: Another metal that has several different forms and is used widely in the metal finishing and textile industries, and in fungicides and wood preservatives.

Formaldehyde: Used as a stabilizer in gasoline and extensively in agricultural products and paper industries, and to produce adhesive resins in wood products and textile treatments. Not present in gasoline but formed as a byproduct of combustion. Also produced when other combustion gases react in the air after being emitted.

Butadiene (1,3): Used to produce tires, hoses, belts, latexes, carpet backings, paper coatings, luggage, appliance and electrical equipment and other products. Evaporates from gasoline.

Acrolein: Used in making plastics, drugs and tear gas. Emitted from vehicles as a byproduct of combustion. Not proven to be a carcinogen, but can cause respiratory problems and permanent lung damage.

Arsenic: Naturally occurring element produced from copper and lead smelters and used mainly for wood preservatives, agricultural products. Thought to be in rock material mined on Minnesota's Iron Range.

Copyright 1998 Star Tribune. All rights reserved.
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