Concepts Important to Understanding Human Health Risk Assessment
A number of concepts and definitions are used in human health risk assessment. Key descriptions include ‘health hazard’, ‘health risk’ and ‘exposure’.
Health Hazard
- A hazard is something that has the potential to cause harm. It could be a biological substance, a chemical, something with specific physical properties or activity.
- A hazard cannot possibly cause harm unless people or some part of the environment are exposed to the risk.
- A health hazard is therefore something that has the probable to cause harm to the health of individuals, groups of people or the entire community.
Health Risk
- Risk is the likelihood (or probability) that a hazard will cause harm.
- A health risk is therefore the likelihood (or probability) that exposure to a health hazard will cause harm.
Exposure
Exposure is the amount (sometimes called a dose) or concentration (i.e. the amount of a hazardous substance in air, soil, water, etc.) that comes into contact with or enters an organism over a known period of time.
Human Health Risk Assessment
- Human health risk assessment is a way of assessing the likely impact of a hazard on the health of an individual, group of people, or community. It uses factual technical information to understand the potential health effects.
- Each human health risk assessment is unique to the specific situation and population group being assessed. The population group being assessed may be an entire community or specific groups within a community, such as workers, children, the elderly, or people with specific health conditions such as asthma.
The five main steps in the human health risk assessment process are:
- Problem Definition: What is the identified problem or situation?
- Hazard Assessment: What are the possible adverse health effects connected with the identified hazards that pose a potential health threat? Understanding the dose-response relationship: What is the dose-response relationship for each adverse health effect identified? What studies are used to obtain this information?
- Exposure assessment: Developing a model of the site or situation, including pathways linking sources of each hazard to people; Collecting and analysing data on each hazard, such as assessing/sampling air, water or soil; Identifying population groups that may be affected and how they may be exposed to each hazard.
- Risk characterisation: This step analyses the above information to assess the extent and nature of past, current or future risks to human health, including communities.
- Community and stakeholder consultation occurs as part of the human health risk assessment process.
- Human health risk assessment is important because it informs the risk management stage. It includes recommended recommendations or actions (if needed) to ensure that human health is protected. Risk communication occurs during the risk management stage.
Environmental Health Risk Assessment
- Environmental health is defined as the aspects of human health that are determined by physical, chemical, biological and social factors in the environment. Environmental health practice involves the assessment, correction, control and prevention of environmental factors that may have adverse effects on health, and the improvement of those aspects of the environment that may improve human health.
- Environmental health risk calculation is a type of human health risk valuation that examines the potential impact of conservational hazards on the health of individuals, usually specific groups or the community as a whole.
- The Australian method to environmental health risk assessment is described in the unhealthy publication Environmental Health Risk Assessment: Guidance on Assessing Human Health Risks from Environmental Hazards 2012, available on the Australian Government Department of Health website.
Who carries out a human health risk assessment?
- People who conduct human health risk assessments typically have advanced degrees in science, engineering, or medicine and typically have expertise relevant to the problem or situation being assessed.
- Human health risk assessors work with experts in toxicology, epidemiology, and chemistry, especially when the assessment involves hazardous materials, including chemicals.
- Human health risk assessors are trained to understand each step of the risk assessment process and to analyze the problem rationally. They break the assessment down into smaller steps and solve each part of the problem using reasoning and logic, like solving a puzzle. The puzzle is reassembled to understand the extent and nature of past, present, or future risks to human health.
- Depending on the problem, government departments and agencies may conduct a human health risk assessment or hire an independent expert to do the work.
When is a human health risk assessment required?
- The decision to conduct a human health risk assessment is made on a case-by-case basis, typically when a major activity or project has the potential to affect human health, and to develop risk management recommendations and measures
- A human health risk assessment helps experts evaluate the overall situation and determine what recommendations or actions, if any, should be taken to ensure the protection of human health.
- Historical, current, or future exposure to chemicals in air, soil, water, food, consumer products, or other materials can be assessed.
Limitations of a Human Health Risk Assessment
- A human health risk assessment is only one tool that can be used to measure and manage environmental health risks.
- In some cases, not all information is available, so the risk assessor may need to make conservative estimates and assumptions. This means that, to ensure the protection of public health, human health risk assessments often overestimate the theoretical risk when there are gaps in knowledge. Environmental health risk assessments are also based on the most sensitive (or vulnerable) people in the community. This allows for predictions of the worst-case scenario in order to make the best decisions about human health risk management.
- It is important for the community to understand that an environmental health risk assessment considers communities or populations as a whole. Environmental health risk assessments identify the nature and extent of past, present, or future health risks, but they do not typically:
identify specific individuals exposed to a chemical:
- compare levels of a chemical measured in individuals or groups of people with its health consequences;
- diagnose illnesses, so they should not replace the advice of a physician or health professional.
- Community members who are concerned about their health or the health of someone they care for should always contact a health professional first.
- In some cases, a government department or agency may commission a private individual or company to conduct a human health risk assessment at its own expense. This may include an additional peer review process to ensure the independence and accuracy of the results.
Conclusion
- Human health risk assessment plays a critical role in identifying, evaluating, and managing potential health risks from environmental, chemical, biological, and lifestyle factors. Through the systematic analysis of risk factors, exposure levels, and population vulnerability, risk assessments help inform regulatory decisions, public health policies, and prevention strategies.
- A well-conducted risk assessment promotes evidence-based actions, improves public safety, and enables communities and industries to proactively reduce health risks. As environmental and social conditions change, continuous improvement in data quality, assessment models, and stakeholder engagement is critical to ensuring accurate and equitable protection of human health.
Frequently Asked Questions
1. What is a human health risk assessment?
A human health risk assessment (HRA) is a scientific process used to evaluate potential risks to human health from exposure to environmental hazards, such as chemicals, pollutants, or biological agents. It helps determine whether a substance is hazardous and at what level of exposure it becomes unsafe.
2. Why are HRAs important?
They are necessary to:
- Protect public health
- Establish safety standards for chemicals and pollutants
- Guide environmental cleanup
- Make regulatory decisions and develop policies
- Assess workplace and community exposure
3. What are the main steps of a human health risk assessment?
The HRA process typically consists of four key steps:
- Hazard identification: What adverse effects can a substance cause?
- Dose-response assessment: At what exposure level do these effects occur?
- Exposure assessment: How, how often, and to what extent are people exposed?
- Risk characterization: What is the perceived health risk and how evident is it?
4. Who conducts a human health risk assessment?
They are typically conducted by:
- Environmental and public health authorities (e.g., EPA, WHO)
- Occupational health authorities
- Toxicologists and environmental scientists
- Consultants from government, industry, or NGOs
5. What types of risks are assessed?
Risk assessments can focus on:
- Chemical risks (e.g., lead, mercury, pesticides)
- Biological risks (e.g., bacteria, viruses)
- Physical risks (e.g., radiation, noise)
- Lifestyle risks (e.g., smoking, diet, physical inactivity)
6. Where are health risk assessments commonly used? Industrial site assessments
- Air and water quality management
- Food safety assessments
- Pesticide and pharmaceutical regulation
- Land remediation and environmental cleanup
- Workplace safety assessments
7. What factors influence human health risk?
- Age, genetic predisposition, and general health of the individual
- Duration and frequency of exposure
- Type of hazard and toxicity
- Environmental and socioeconomic conditions
8. Can health risk assessments prevent disease?
Yes. Although they do not cure diseases, risk assessments help identify and reduce potential risks before they cause harm, allowing for preventive measures such as policy changes, environmental cleanup, or protective measures.
9. How accurate are human health risk assessments?
Human health risk valuations are based on the best available science, but they include uncertainties, especially when human data are limited. To address this, safety factors and conservative assumptions are used to protect vulnerable populations.
10. How can communities use the results of a risk assessment? Communities can use the results of a human health risk assessment to:
- Advocate for a cleaner environment
- Assess potential health risks to local communities
- Make informed land-use decisions
- Communicate with policymakers and public health officials