How does the Site Assessment and Consultation (SAC) unit evaluate a site?
The evaluation process has four parts:
(1) Evaluating Exposure
The mere presence of a toxic chemical does not necessarily mean that people are being exposed to a potential health hazard. People have to come in contact with the chemical-in sufficient amounts-before any health effects can occur.
- Before a chemical can affect human health, there must be a complete "exposure pathway." This means that there must be a route by which a hazardous chemical can get into people's bodies at levels that can cause harm.
- A complete exposure pathway includes all of the following:
- a source of contamination, such as a leak, spill, or other discharge to the environment;
- an environmental "medium" (air, water, or soil) that can carry the contamination; and
- a person or people who come in contact with the contaminated medium.
People may come in contact with contaminants in a number of ways. The most common routes of exposure are skin contact, inhalation, and ingestion. In addition, a fetus can be exposed to toxic chemicals that have entered its mother's body and have passed through the placenta.
To evaluate exposure, MDH scientists review information about environmental conditions at the site. MDH determines from available information how much contamination is present, where it's found, and how people might be exposed to it.
(2) Evaluating Toxicity
If there is evidence that people are being exposed to contaminants -or that they could be exposed- MDH scientists will seek to determine if there might be any potential health effects on the community. The evaluation is based on the best available scientific information.
When investigating public health concerns, MDH scientists look at both toxicity and exposure.
- "Toxic" means "poisonous." Some chemicals can be very toxic. This means that they are harmful even at very low levels of exposure. Others may be much less dangerous, even at relatively high levels of exposure. The toxic effects of a chemical can also vary from one person to another, based on factors such as age, body weight, nutritional status, the exposure route, and a person's genetic makeup.
- The amount of chemical and length of time of exposure are also important in determining whether a public health threat is present. Brief exposure to a small amount of a highly toxic material can sometimes be as dangerous as exposure to a large amount of a low toxicity material for a long period.
(3) Characterizing Health Concerns and Developing Recommendations
MDH issues reports outlining our conclusions about any potential public health concerns posed by a hazardous chemical site. We also make recommendations for preventing or reducing human exposure to contaminants.
The role of MDH in sites where there are contaminant releases is primarily advisory, not regulatory. For that reason, our evaluations typically recommend actions to be taken by other agencies that do have regulatory authority--including the U.S. Environmental Protection Agency (EPA), the Minnesota Department of Agriculture (MDA), and the Minnesota Pollution Control Agency (MPCA).
However, if there is an immediate health threat, MDH will issue a public health advisory, warning people of the danger. At the same time we work in cooperation with others to resolve the problem.
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(4) Obtaining Input from Interested Parties
The evaluation process is interactive. MDH starts by soliciting and evaluating information from government agencies, the community surrounding the site and the organizations or companies responsible for cleaning up the site or operating the facility.
MDH has a "cooperative agreement" with the federal Agency for Toxic Substances and Disease Registry (ATSDR) for the investigation of hazardous chemical sites. ATSDR, an agency of the U.S. Public Health Service, provides technical and financial support to MDH.
MDH also works regularly with the MPCA, MDA, local health departments and communities across the state, as well as with the U.S. EPA.
See our Contact Us page for information about how to contact the Site Assessment and Consultation Unit.