Academic journal article Environmental Health Perspectives

Human Exposure: The Key to Better Risk Assessment

Academic journal article Environmental Health Perspectives

Human Exposure: The Key to Better Risk Assessment

Article excerpt

For decades, the citizens of Libby, Montana, knew something was awry in their rural community. Every year, more and more residents were developing respiratory problems such as emphysema and mesothelioma. The problems often became fatal. In fact, by fall 2000, there were more than 190 such deaths by some estimates. Residents had long suspected a vermiculite mine, the town's chief employer for nearly 70 years, as the source of the maladies. Yet, no one knew for sure.

In November 1999, the federal government investigated. Besides vermiculite, the mine, which was shuttered in 1990, was found to have released tons of tremolite-actinolite into the environment during operations. Tremolite-actinolite, naturally occurring mineral fibers, are rare and highly toxic forms of asbestos, and exposure can manifest decades later in chronic respiratory diseases such as asbestosis, emphysema, and rare cancers.

As far back as the mid-1950s, state health officials had reported the presence of toxic asbestos dust in the mine, but no one had followed up to study possible exposures or health effects on the town's residents. According to investigators from the Agency for Toxic Substances and Disease Registry (ATSDR), the mine may be the most significant single source of toxic asbestos exposure in U.S. history.

Situations like the one in Libby reveal that there are serious flaws in the way the United States approaches environmental health. And monitoring of human exposure to environmental agents is often the weakest component of environmental health work, severely limiting risk assessment capabilities.

Across key government agencies, experts agree that current efforts to monitor human exposure to environmental agents are inadequate. Good data on the type, pattern, and magnitude of human exposures are in short supply. A series of recently released reports by private and public institutions support such assertions and, coupled with a rising incidence of chronic diseases from asthma to lupus, are spurring calls for systemic improvement.

Not Enough Data

"The bottom line in exposure tracking is that we know very little about what the public is being exposed to or the actual levels of the exposure." So concludes America's Environmental Health Gap: Why the Country Needs a Nationwide Health Tracking Network, released in September 2000 by the Pew Environmental Health Commission at the Johns Hopkins School of Hygiene and Public Health in Baltimore, Maryland.

Chemical exposures is one arena where data are sorely lacking. Together, the leading national exposure assessment surveys--run by the Department of Health and Human Services and the U.S. Environmental Protection Agency (EPA)--monitor exposure to a mere 6% of the 1,400 potentially hazardous high production volume (HPV) chemicals in common use, finds a May 2000 General Accounting Office (GAO) report titled Toxic Chemicals: Long-Term Coordinated Strategy Needed to Measure Exposures in Humans. (With a total of 2,800 such chemicals, HPV chemicals are those that are produced or imported at volumes of one million or more pounds per year.) Moreover, states the report, the information obtained is often insufficient to identify smaller populations at high risk. To compound difficulties, no laboratory method has been developed for measuring concentrations of most chemicals in human tissues. Furthermore, even if measured accurately, would scientists know the significance of the measurement?

"Society spends an enormous amount of money on monitoring the environment--on water utilities alone we spend more than a billion dollars--but we have not adequately looked at exposures to the human population," says Richard Jackson, director of the National Center for Environmental Health at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia.

Although some federal programs are seeing expansion, "there's a real lack of quality exposure information," says toxicologist Scott Masten, who heads the NIEHS Office of Chemical Nomination and Selection. …

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