The Four Steps of Risk Assessment

Though risk assessment projects use different methods and techniques, all go through four basic steps to characterize risk.

Step 1 - Hazard Identification

After determining an area to study, IDEM samples the affected environment, analyzes the samples, and identifies chemicals that may contribute to increased risk.

IDEM learns about potential health hazards from many sources. Most of the time, a national screening tool, such as U.S. EPA's Toxic Release Inventory, will identify areas in the state that may have an elevated risk hazard. In some cases, the investigation of a citizen complaint will lead to the agency conducting a risk assessment.

The initial investigation of a site usually includes collecting samples and identifying potential sources of suspected risks. The samples are run to identify levels of a range of chemicals, not just suspected risk chemicals. If one or more chemicals warrant further study, the agency begins a formal risk study.

Step 2 - Exposure Assessment

Long-term monitoring is established, if necessary. Chemical levels are studied.

Exposure assessments are performed for the hazardous chemicals identified. Regardless of what prompted the study, IDEM begins scientifically measuring the impacted environment to determine potential human exposure. This step may require years of sampling or just a simple surface wipe. The data is processed and quality-assured. Additional considerations may need to be included to estimate chemical exposure, such as meteorological data.

IDEM studies chemicals that enter the body through inhalation, absorption and ingestion. IDEM studies the daily lives and habits of people living in the area. Different exposures will allow the chemical to access different organs, affecting the body in dramatically different ways.

Step 3 - Dose-Response Assessment

The dose-response factors are evaluated based on the needs of the risk assessment and the appropriate factor is chosen.

At the same time as the Exposure Assessment is being conducted, the appropriate dose-response factor is chosen for chemicals being studied. Scientists have conducted studies to determine a person's risk for each exposure path. When choosing a dose-response factor to apply to a risk assessment study, the scientists conducting the study will use the dose-response factor that best fits the study's parameters.

Step 4 - Risk Characterization

The monitoring data is evaluated based on the appropriate dose-response factor and the risk for the area is calculated.

Once the exposure assessment has determined an exposure level and an appropriate dose-response factor, the increased risk in the study area can be calculated. However, the risk calculation will not represent the actual chance of developing symptoms/diseases. Health-protective assumptions made during the risk calculation will protect overall health, but end up raising the estimated number of calculated symptoms/diseases.

The last step in a risk assessment is to communicate the results to the public.