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Risk Assessment

Are you concerned about the increasing levels of green house gasses in the atmosphere, the decline in the coral reefs, the presence of toxic chemicals in the environment, or the quality of the water you drink? Do you enjoy working on complex problems? If so, then the field of environmental risk assessment may be right for you.

Environmental risk assessment has grown in the last 30-40 years as people have realized their actions can have adverse effects on the environment. The publication in 1962 of Rachel Carson's landmark book, Silent Spring, describing the hazards to wildlife of the widely used pesticide DDT was a wake-up call that chemicals may have negative, as well as positive, effects on the environment (including humans).

The 1970s saw the passage of environmental protection legislation such as the Clean Water Act, Clean Air Act, and Superfund (Comprehensive Environmental Response, Compensation, and Liability Act). All this legislation required risk assessments.

Risk assessment is the characterization of the potential adverse health effects resulting from human and ecological exposure to environmental hazards. The risk assessment process, which includes the following steps, is complex:

Hazard identification is the analysis of an environmental situation to ascertain if there is the potential for exposure of an organism (including a human) or ecosystem to an environmental stressor that may cause harm.

Dose-response assessment is the process of characterizing the relation between the dose of an agent received by a receptor (organism or ecosystem) and the incidence of an adverse effect on that receptor.

Exposure assessment is the process of measuring or estimating the intensity, frequency, or duration of human or ecological exposure to agents currently in the environment or that may be present in the future.

Risk characterization is the process of estimating the incidence of an adverse effect under the conditions of exposure described in the exposure assessment. It also includes the narrative description of the meaning of the assessment, including uncertainties in the preceding steps.

Each of the steps requires the collection of data (e.g., lead concentrations in soil or water) and/or the use of mathematical models (e.g., those that describe the movement of contaminants in the environment or define the cancer incidence from exposure to levels of uranium).

Risk assessments have become part of the analysis a proposed chemical or other product must undergo before it may be placed on the market.

A successful environmental risk assessment requires the talents of many academic disciplines-chemistry, physics, biology, ecology, geology, hydrology, and engineering. Because of their skills in analyzing data and computations, statisticians can play a role in each of the steps above.

Additionally, a statistician can play a key role in the process because of the complexity of a risk assessment. Data or modeling uncertainty in any of the steps may have a significant effect on the results and meaning of the assessment. Therefore, the description of uncertainty in the assessment, which is a skill area of statisticians, becomes a crucial part of communicating the results of a complex assessment.

People who perform risk assessments are employed by all those dealing with environmental issues: government regulatory agencies, companies whose work may affect the environment, and nongovernmental organizations involved in environmental protection issues.