What is exposure science?
The study of human contact with chemical, physical, or biological agents occurring in their environments
Can address past, present, or expected exposures
Examples of exposure pathways?
- Groundwater contamination
- Radiation
- Multi-pollutants
What are the objectives of exposure science?
- Follow trends/status (identify pollutants of concern)
- Risk assessment
- Epidemiologic studies (exposure assignment, exposure validation)
- Examine disease etiologies
What are the four steps of risk assessment?
- Hazard ID
- Exposure Assessment
- Dose Response Assessment
- Risk Characterization
How can we quantify exposures?
- Direct measurements (at point-of-contact)
- Scenario modeling/evaluation (hypothetical exposures)
- Biomonitoring (biomarkers, excretion levels, historical exposures)
These approaches are independent of each other
What are some issues in planning risk assessments?
- Cost
- Statistical power (generalizability, detecting significance)
- Time
- Uncertainty
Applications of direct measurement
Environmental air/water pollutants, radiation, pesticides
Advantages of direct measurement
Direct measurement, accurate
Disadvantages of direct measurement
Expensive, time-consuming, cumbersome, limited range of pollutants
Applications of modeling/evaluation
Groundwater, indoor air, soil sampling at waste sites
Advantages of modeling/evaluation
Inexpensive; can be prospective
Disadvantages of modeling/evaluation
Assumptions; validation required
How can we measure ambient concentrations?
Dispersion models
How can we measurer ground level PM?
Remote sensing
Applications of biomonitoring
Lead, dioxin, VOCs (volatile organic compounds)
Advantages of biomonitoring
Gives idea of internal dosage; biologically-relevant exposure; historical exposures
Disadvantages of biomonitoring
Requires pharmacokinetic info; potentially expensive & invasive
What is the exposome?
The measure of all the exposures of an individual in a lifetime and how those exposures relate to health.
How can we characterize the exposome?
Top-Down and Bottom-Up
Advantages of “Bottom-Up” characterization
- Focus on external, familiar sources & products
2. Direct policy and intervention implications
Disadvantages of “Bottom-Up” characterization
- Many, many pathways
- Unknown exposures
- How do we evaluate mixtures/synergistic relationships?
Advantages of “Top-Down” characterization
- Efficient (both endogenous & exogenous)
- Represents totality of exposure
- Hypothesis-generation
- Focus on unknown causes of disease
Disadvantages of “Top-Down” characterization
- Hard to define “normal”
- Inter-individual variability
- Agnostic, not hypothesis-driven
What is the “Top-Down” approach?
Untargeted method utilizing biological systems methods
