Human Health Risk Assessment

A Human Health Risk Assessment (HHRA) is the process evaluates the likelihood that adverse health effects are occurring or may occur as the result of human exposure to one or more stressors through one or more exposure pathways. In Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or Resource Conservation and Recovery Act RCRA Corrective Action (RCRA) actions HHRA specifically means a qualitative and/or quantitative evaluation of actual or potential impacts of restoration site contaminants on human health. There are several classes of human receptors, based on age or gender, and include special populations such as those with compromised immune systems. For risk to human health to exist, the contaminant must have the ability to cause an adverse effect and there must be a completed exposure pathway (e.g., ingestion, inhalation) over a period long enough and at a high enough level to cause an adverse effect.

The Army takes its commitment to protecting human health and the environment seriously and the HHRA helps determine if a risk to human health exists at Army restoration sites. An HHRA is an integral part of the Remedial Investigation/Feasibility Study (RI/FS) process and is designed to support risk management decision-making. The RI component of the process characterizes the nature and extent of contamination, and estimates risk to those people potentially impacted by contaminants at or from the site. The FS component develops and evaluates remedial options to mitigate any existing or potential risk. Even though themajority of DoD sites are not designated as Superfund sites, HHRAs are performed using the U.S. Environmental Protection Agency (EPA) Risk Assessment Guidance for Superfund, known as RAGS. Volume I Human Health Evaluation Manual (Part A) Interim Final, Dec 1989 at http://www.epa.gov/oswer/riskassessment/ragsa/inde... is the first and most used of six parts (A – F) detailing the lengthy and very conservative processes.

Following the US EPA Superfund guidance for HHRAs, we use a multi-step process, with five basic steps:

1. Planning and Scoping
2. Hazard Identification
3. Dose-Response Assessment
4. Exposure Assessment
5. Risk Characterization

The EPA begins its risk assesment by first planning and conducting research; Hazard identification looks at whether a stressor has the potential to cause harm to humans; Dose-response assessment examines the numerical relationship between exposure and effects; Exposure assessment covers what is known about the frequency, timing, and levels of contact with a stressor; and Risk characterization details how well the data support conclusions about the nature and extent of the risk from exposure to stressor(s).

The science of HHRA has really expanded, and EPA offers many guidance documents at the EPA website. For assistance with specific HHRA issues, individuals or installations may contact the Army Public Health Center (APHC), U.S. Army Combat Capabilities Development Command Chemical Biological Center, the U.S. Army Corps of Engineers (USACE), U.S. Army Corps of Engineers Environmental and Munitions Center of Expertise (EM CX) Directorate, or the USAEC individuals who specialize in risk assessment protocols, ecology, toxicology and natural resources.