Planning a Human Health Risk Assessment

Planning - There is a need to make judgments early when planning major risk assessments regarding the purpose, scope, and technical approaches that will be used. To simplify our discussion of planning the following structure focuses on human health risk assessment.

Risk assessors will typically ask the following questions when planning a human health risk assessment:

Who/What/Where is at risk?

Individual
General population
Lifestages such as children, teenagers, pregnant/nursing women
Population subgroups - highly susceptible (for example, due to asthma, genetics, etc.) and/or highly exposed (for example, based on geographic area, gender, racial or ethnic group, or economic status)

What is the environmental hazard of concern?

Chemicals (single or multiple/cumulative risk)
Radiation
Physical (dust, heat)
Microbiological or biological
Nutritional (for example, diet, fitness, or metabolic state)
Socio-Economic ( for example, access to health care)

Where do these environmental hazards come from?

Point sources (for example, smoke or water discharge from a factory; contamination from a Superfund site)
Non-point sources (for example, automobile exhaust; agricultural runoff)
Natural sources

How does exposure occur?

Pathways (recognizing that one or more may be involved)
- Air
- Surface Water
- Groundwater
- Soil
- Solid Waste
- Food
- Non-food consumer products, pharmaceuticals
Routes (and related human activities that lead to exposure)
- Ingestion (both food and water)
- Contact with skin
- Inhalation
- Non-dietary ingestion (for example, "hand-to-mouth" behavior)

What does the body do with the environmental hazard and how is this impacted by factors such as age, race, sex, genetics, etc.?)

Absorption - does the body take up the environmental hazard
Distribution - does the environmental hazard travel throughout the body or does it stay in one place?
Metabolism - does the body breakdown the environmental hazard?
Excretion - how does the body get rid of it?

What are the health effects?

Example of some health effects include cancer, heart disease, liver disease and nerve disease.

How long does it take for an environmental hazard to cause a toxic effect? Does it matter when in a lifetime exposure occurs?

How long?
- Acute - right away or within a few hours to a day
- Subchronic - weeks or months (for humans generally less than 10% of their lifespan)
- Chronic - a significant part of a lifetime or a lifetime (for humans at least seven years)
- Intermittent
Timing
Is there a critical time during a lifetime when a chemical is most toxic (e.g., fetal development, childhood, during aging)?

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