Comparison of risks from outdoor and indoor exposure to toxic chemicals

Our plain-English summary of Comparison of risks from outdoor and indoor exposure to toxic chemicals, by L.A. Wallace (Environmental Health Perspectives, 1991).

The study

• Author: L.A. Wallace
• Journal: Environmental Health Perspectives
• Published: 1991;95:7-13
• Cited by: 70 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Environmental Protection Agency TEAM (Total Exposure Assessment Measurement) Studies have measured exposures of about 800 persons to 25 volatile organic compounds (VOCs) and exposures of about 300 persons to 32 pesticides. These persons were selected to represent more than 1 million residents of industrial manufacturing cities such as Bayonne and Elizabeth, New Jersey, and Los Angeles, California; cities with light industry, such as Greensboro, North Carolina, and Baltimore, Maryland; rural areas such as Devils Lake, North Dakota; and cities with high pesticide use such as Jacksonville, Florida, as well as low-to-moderate pesticide use such as Springfield, Massachusetts. The TEAM data provide an opportunity to estimate the risks from airborne exposure to a number of suspected carcinogens for a substantial number of persons residing in a wide variety of urban, suburban, and rural areas. Because all of the TEAM Studies measured outdoor concentrations near the homes of the participants, it is possible to apportion the risks between outdoor and indoor sources. Upper-bound lifetime risks of cancer are calculated for both indoor and outdoor sources of 12 VOCs and about 23 pesticides measured in the TEAM Studies. These risk calculations are supplemented by calculations based on other studies for some additional pollutants, including radon and environmental tobacco smoke. The relationship of these upper-bound risk estimates to "best-guess" values is discussed. Sharper estimates of risk based on identifying population subgroups exposed to major sources are also discussed. Important gaps in our knowledge of exposure measurements are identified, e.g., particulates (including polyaromatic hydrocarbons); 1,3-butadiene, asbestos, chromium, cadmium, arsenic, vinyl chloride, methylene chloride, and most polar organics.

In plain English

This paper by an EPA researcher calculated cancer risks from chemicals in household and outdoor air; it did not study asbestos. It used exposure measurements from EPA's TEAM Studies and EPA cancer potency values. The author estimated lifetime cancer risks from breathing 12 volatile organic compounds and 23 pesticides, and split those risks between indoor and outdoor sources. The estimates were upper-bound values except for benzene, whose estimate was a mean based on human studies. Seven organic compounds, including benzene and chloroform, and four banned pesticides exceeded a one-in-a-million risk level at least tenfold. Indoor sources accounted for 80 to 100% of the airborne risk for most chemicals; carbon tetrachloride was the only one whose risk came mostly from outdoors. With formaldehyde and 1,3-butadiene added, two chemicals the TEAM Studies did not monitor, the combined upper-bound risk for 37 organic chemicals, about 1 in 1,000, appeared similar to estimates for radon and passive smoking. The author stressed that these estimates were very uncertain, but concluded they supported EPA rankings placing indoor air pollution among the greatest threats to public health. Asbestos appeared only in the abstract, as a gap in exposure knowledge.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Risk assessment: calculation of lifetime cancer risks from previously collected exposure measurements combined with EPA potency values; upper-bound estimates except for benzene, whose estimate is a mean based on human epidemiology
• Who was studied: Residents of U.S. cities measured in EPA's TEAM Studies. For volatile organic compounds, about 750 persons in 6 urban areas, from studies in 8 cities between 1980 and 1987. For pesticides, 173 persons in Jacksonville, Florida, and 85 persons in Springfield/Chicopee, Massachusetts, measured between 1986 and 1988.
• Exposure: Airborne exposure (personal, indoor and backyard outdoor air) to 12 volatile organic compounds and 23 pesticides. Asbestos was not measured; it was listed only as a gap in knowledge of exposure measurements.
• Main results:
  • Seven volatile organic compounds (benzene, vinylidene chloride, p-dichlorobenzene, chloroform, ethylene dibromide, methylene chloride, carbon tetrachloride) and four pesticides (chlordane, heptachlor, aldrin, dieldrin) exceeded the one-in-a-million (10 to the minus 6) risk level by a factor of 10 or more.
  • Indoor sources accounted for 80 to 100% of the total airborne risk for most of the chemicals studied.
  • Carbon tetrachloride was the only target chemical for which outdoor sources accounted for a majority of the airborne risk.
  • When the upper-bound estimates were divided by 7 or 10 to give best estimates, benzene emerged as the single chemical with the highest risk of the 35 considered.
  • Formaldehyde and 1,3-butadiene were not monitored in the TEAM Studies; their risks were estimated separately from other data.
  • The combined upper-bound risk of about 1 in 1,000 (10 to the minus 3) for 37 predominantly indoor organic chemicals appeared similar to the risks estimated for radon and passive smoking. The 37 are the 35 TEAM chemicals plus formaldehyde and 1,3-butadiene.
• The authors' conclusion: The author concluded that, despite large uncertainty, the findings supported two EPA comparative risk rankings that indoor air pollution is one of the greatest threats to public health of all environmental problems.
• Limitations the authors state:
  • The author stated that the absolute sizes of the upper-bound risks are very uncertain.
  • The author stated that potencies come largely from animal studies and that the estimates could be wrong by factors of 10, 100 or more.
  • The author stated that information on exposure or potency was inadequate to calculate risk for several chemicals, including vinylidene chloride, methylene chloride, 1,3-butadiene, formaldehyde, ethylene dibromide, chlorpyrifos and diazinon.

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