Aggregate Exposure and Cumulative Risk Assessment—Integrating Occupational and Non-occupational Risk Factors

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Table 1 Glossary of Key Terms

Key Term	Definition
Aggregate risk	The sum of risks associated with exposures from multiple pathways and routes
Biomarkers	Internal measures or markers of exposures or effects for a chemical or agent in the body
Cumulative risk	The combined risk from exposure to chemical and no-nchemical stressors, including the possibility that such exposures may modify the toxic effects observed or their severity through interactive processes
Exposome	The measure of all the exposures of an individual in a lifetime and how those exposures relate to health
Exposomics	The study of the exposome, which relies on the application of internal and external exposure assessment methods
Occupational exposure limit	A threshold below which adverse health effects would not be expected to occur among workers; used as a risk management tool for minimizing occupational health risk through characterization and control of exposure to workplace hazards
Total Worker Health	The NIOSH strategy to integrate occupational safety and health protection with general health promotion to prevent worker injury and illness and to advance overall worker health and well-being
Toxicodynamics	The effects of a chemical or agent in the body induced at the level of the affected tissue
Toxicokinetics	The disposition of a chemical or agent in the body

Figure 1 Illustration of relative contribution to exposure. This figure illustrates a theoretical case study of aggregate exposure to organic solvents. In this scenario, exposures may occur via multiple exposure pathways and routes. The relative contribution to total exposure to organic solvents is proportionally represented for each of the primary exposure routes and further delineated by setting, (i.e., occupational vs. non-occupational).

Figure 2 Illustration of the relationship between key factors considered in cumulative risk assessment. This figure illustrates key risk factors that may contribute to aggregate and cumulative risk. The primary factors are organized into three categories: (1) occupational factors, (2) non-occupational factors, and (3) individual factors. For each category, examples of the primary settings, sources of risk, exposure routes, key stressors, and effects are included to aid in illustrating considerations that should be included in assessing aggregate and cumulative risk to various hazards.

Table 2 Critical Factors and Key Questions to Inform and Guide Aggregate and Cumulative Risk Assessments

Critical factors	Key questions
• Advances in exposure science	• Which mixtures are most important from a public or occupational health perspective?
• Increased technical capabilities associated with exposure monitoring and analytical techniques	• What is the nature (i.e., duration, frequency, and timing) and magnitude (e.g., exposure concentration and dose) of relevant cumulative exposures for the population of interest?
• Application of toxicokinetics and toxicodynamics data to characterize the consequences and variability of mixed exposures to environmental stressors	• What is the mechanism (e.g., toxicokinetic or toxicodynamic) and consequence (e.g., additive, less than additive, more than additive) of the mixture's interactive effects on exposed populations?^(^63^)
	• What does one do with such exposure information (i.e., understanding variables that define contact with environmental stressors and the factors that influence the contact)?^(^60^)
	• What roles does exposure science play in situations beyond observational analyses and interpretation?^(^60^)

Figure 3 Case study of potential risk factors included in the assessment of cumulative risk for hearing loss. Note: The percentages indicated represent hypothetical values of the occupational, individual, and non-occupational contributions that might be determined for comparison of the sources and opportunities where interventions and controls might best be provided.

Sexton, K., andD. Hattis: Assessing cumulative health risks from exposure to environmental mixtures - three fundamental questions. Environ. Health Perspect. 115(5):825–832 (2007).

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