In the past few decades there has been a growing awareness of the health hazards of
chemicals present in the environment (Davis et al. 2001). Accordingly, researchers have
reviewed early risk assessment techniques. Since the United States Environmental Protection
Agency (USEPA) promulgated the Interim Procedures and Guidelines for Health Risk and
Economic Impact Assessments of Suspected Carcinogens (Train 1976) in 1976, strict health
and economic impact risk assessments have been an important part of the regulatory process.
Subsequently, the EPA generated water quality standards for 64 contaminants (USEPA 1980),
as well as its first quantitative description of risk assessment. The groundwater nitrate health
risk assessment model used in the present study is based on integrating the principles of risk
assessment from a report published by the National Academy of Science (NAS): Risk
Assessment in the Federal Government:Managing the Process (NRC 1983; commonly referred
to as the Red Book) (USEPA 2001). According to this publication, human health risk assessment
includes four steps: