Effects of Contaminants on Human Health

Understanding the effects chemical contaminants have on human health is not a simple or straightforward process. One reason for this challenge is because there are approximately 15,000 chemicals produced and less than half of those have ever been tested to determine their impact on human health. Add to the quantity of chemicals, the many possible interrelationships between all of the chemicals and the unique genetic and environmental circumstances of every human, predicting or confirming that a disease has been caused by a chemical contaminant is extremely complicated.This page will describe exposure pathways, contaminant-based disease detection, and provides additional web links.

Contaminant-Based Disease Detection

One of the biggest fears of exposure to contaminants is cancer. Some contaminants are known carcinogens (chemicals that cause cancer) while others are only suspected. An example of a known carcinogen is asbestos; a suspected carcinogen is DEHP [di(2-ethylhexyl)phthalate] - a component of plastic. For many contaminants, scientists do not always know how much exposure will cause harm or disease. Scientists do not know about the risk to humans because many studies are conducted on rats and mice rather than on humans. (It would be unethical to purposefully expose humans to high doses of these chemicals.)

Environmental contaminant exposures can be related to other diseases in addition to cancer. Such diseases include immune deficiencies (from polychlorinated biphenyls or PCBs), asthma (from particulates), reproductive disorders (from DEHP), neurological (brain and nerve) disorders (from lead), blood disorders (from benzene), liver disorders (from dioxins) and other health problems such as endocrine, gastrointestinal or skin conditions. There are many other conditions that are suspected as being caused by contaminants, but physicians and scientists are not certain of the cause. Most physicians are not trained in the complex analysis of chemical exposures. In addition, special testing by special laboratories is needed to test blood or tissue for many of the suspected causative agents (chemicals). This uncertainty can make citizens anxious and angry that their conditions are not being considered seriously. It is important to describe your concerns to your physician and ask for a referral to a specialist.

Some people might think hazardous chemicals should be eliminated entirely. However, it is difficult, to weigh the possible harm of exposure versus the need for the chemical. For example, asbestos is an important substance in fire protection and cannot be completely eliminated from use. Therefore, means to protect human health from exposure has become a priority.

The ATSDR will actually conduct exposure investigations using an Exposure-Dose Reconstruction Analysis (EDRA). ATSDR takes environmental samples and conducts a computer model to estimate exposure levels. The State Health Department may also conduct these analyses under contract with the ATSDR.

ATSDR typically requires additional information in the following categories (ATSDR, 1994):

  1. Contaminant concentrations in all off-site media to which the public may be exposed;
  2. An appropriate detection limit and level of quality assurance/quality control (QA/QC) in samples to ensure the resulting data are adequate for assessing possible human exposures;
  3. Discrete samples that reflect the potential range of exposure of the public;
  4. Surface soil and sediment samples not deeper than 3 inches;
  5. More extensive biota studies, and analyses of edible portions only;
  6. More ambient and indoor air sampling; and
  7. Lists of physical hazards and barriers to site access.

Finally, citizens can help look for disease clusters themselves. A cluster is an unusually high number of health events found at similar times in a given location. If you suspect you or your community has been exposed, it is important to gather information to help identify a cluster. The ATSDR can provide guidance about the kind of environmental data needed to assess public health related to toxic substances. This website provides the details of an environmental public health assessment.


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