> [!SUMMARY] > ... See [[Risk]] and [[Definitions/Human Health Risk Assessment|Human Health Risk Assessment]] definitions. See [[HHRA following CERCLA Guidance]] ## What is Human Health Risk Assessment? Human health risk assessment, or HHRA, is a scientific and technical process to investigate and characterize the nature and magnitude of [[risk]] to human health for various populations (residents or recreational visitors, both children and adults, and adult workers) exposed to chemical stressors in the environment, for example, chemicals such as arsenic or mixtures of many organic chemicals such as in oil spills that have contaminated soil or groundwater¹. HHRA involves a multi-step process related to the collection of data and information, including the magnitude of the levels of chemicals in the environment, assessing how chemicals are distributed and move through the environment, how receptors are exposed, using available information on chemical toxicity to estimating risks from potential exposure, and discussion of the uncertainties related to the risk assessment process. HHRA conducted as part of a Superfund or state-led cleanup are used to assess how threatening a site where hazardous waste has been released is to human health and the environment. **HHRA often is an iterative process**. The assessors use initial information to identify the factors that are likely to most influence risk from identified stressors or potential stressors. Assessors then identify and fill data gaps as feasible to refine their assessment of risk. With better data and information, the risk assessors and risk managers might further refine the scope of the risk assessment, which can guide further data collection or more realistic assumptions. ## How to conduct a Human Health Risk Assessment? Following a planning and scoping stage, where the purpose and scope of a risk assessment is decided, the risk assessment process usually begins by collecting measurements that characterize the nature and extent of the hazard in the environment. For example, chemical concentrations in soils could be measured around the source of a spill. Information needed to predict how the contaminants may behave in the future also could be collected. Based on the results of the planning and scoping phase, the risk assessor evaluates the frequency and magnitude of human and ecological exposures that may occur. Multiple lines of evidence are used to estimate potential consequences of contact with the contaminated medium, both now and in the future. Both the nature and extent of exposure and the effects of a stressor on humans or ecosystems are considered together. To characterize risks, the assessor predicts the probability, nature, and magnitude of the adverse effects that might occur. Risk assessments should be based on a very strong knowledge base. Reliable and complete data on the nature and extent of contamination or occurrence of other stressor would be ideal. Understanding the movement and fate of chemicals, microbes, or other agents in the environment is needed. The risk assessor obtains available information that quantifies the relationships between the magnitude and frequency of human and ecological exposure and adverse outcomes. In real life, however, information is usually limited for one or more of these key information needs. This means that risk assessors often must estimate exposures and use judgment to calculate risks. Consequently, all risk estimates include uncertainty. For this reason, a key part of all good risk assessments is a fair and open presentation of the uncertainties, including data gaps and limitations of models used to estimate exposure and effects. The final phase of the assessment, risk characterization, includes both quantitative and qualitative descriptions of risk. The assessor clearly characterizes how reliable (or how unreliable) the resulting risk estimates really are. In general, where information is lacking, assessors use health protective assumptions, particularly in the early stages of a risk assessment. Risk managers then use this information to help them decide how to protect humans and the environment from contaminants or other stressors. Note that “risk managers” can be federal or state officials whose job it is to protect the environment, business leaders who work at companies that can impact the environment, or private citizens who are making decisions regarding risk. The risk managers can conclude that more information is needed to reduce uncertainty in key factors driving risks and can request further data collection and a refined assessment. Though vapor intrusion is common assessed in HHRAs, there are specific considerations related to assessing [[Vapor Intrusion Risk Assessment]]. See [[HHRA following CERCLA Guidance]]. ## Key HHRA Steps * Investigation * Collecting environmental sampling data [[Data Collection and Analysis]] * Collecting other site-related information * Assessing Risk * [[Data Assessment]] * Assessing concentration data ([[Assessing Data for HHRA]]) * Assessing data quality * [[Toxicity Assessment]] * [[Exposure Assessment]] * [[Risk Characterization]] * Interpretation and Decision Making * Risk assessment results * Regulatory criteria * Regulatory framework/risk management ## Glossary [Risk Assessment Glossary | US EPA](https://sor.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=Risk%20Assessment%20Glossary) Source(s): ¹See [About Risk Assessment | US EPA](https://www.epa.gov/risk/about-risk-assessment#whatisrisk) *** 2023 cloudedknowledge.net