Tiered aggregate exposure assessment - when to launch
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The document discusses criteria for determining whether to conduct an aggregate exposure assessment or a simple exposure assessment for a chemical. It provides definitions for key terms and outlines a general process for deciding between the two types of assessments. This includes considering the purpose of the assessment, potential routes and pathways of exposure, and whether exposures can be aggregated or if the population needs to be subdivided. An example case study comparing exposure to a pesticide from food and a consumer product is analyzed in more detail.
Tiered aggregate exposure assessment - when to launch
- 1. Criteria for using “simple” versus aggregate exposure assessmentJohn Cherrie for the TAGS Group
- 2. Summary…Some definitionsWhen not to do an aggregate exposure assessmentKnowing why you want to do the assessmentCriteria for deciding what type of assessment is neededAggregating routesAggregating pathwaysAn example – pesticide7/6/102TAGS workshop
- 3. Talking the same language - definitionsExposure scenario - a set of circumstances through which someone may become exposed to the substance of interestSources, pathways and exposure routesoutdoor motor vehicle > outdoor air > breathing zone > inhalationExposure, intake and uptake7/6/103TAGS workshop
- 4. Criteria…When should we launch an aggregate exposure assessment? orWhen is it appropriate to just do a simple exposure assessment?7/6/104TAGS workshop
- 5. Aims and objectives…Define the population at riskSet out the exposure scenarioSpecify the toxicological / health effects of interest for each route of exposureRisk assessment, ranking routes, ranking pathways?Note: aggregating across routes more problematic than across sources / pathways7/6/105TAGS workshop
- 6. General scheme…7/6/106TAGS workshopDefine the purpose of the exposure assessmentPurpose to distinguish between pathways/routes? YAEANIgnoring the magnitude of exposure, is there a basis for aggregation across routes?Screening of relative magnitude of routes: is one route more important than others?NYNYNCan we subdivide the population to simplify the assessment?Ignoring the magnitude of exposure, is there a basis for aggregation across sources/ pathways?Screening of relative magnitude of different sources/pathways: is one more important than others?NYYNYSEA
- 7. Specific issues…Subdividing the population:Consumers, workers, people only exposed from the environmental pollution (i.e. on exposure)Age, gender, socioeconomic status etc (i.e. on susceptibility)Considering the health effectsMore than one route must be linked to the same systemic effects If these systemic effects are a result of acute exposure, then exposure by more than one route must happen at the same time, or within the same (short) time window 7/6/107TAGS workshop
- 8. Account for magnitude of exposure…Exposure “negligible” or not by route?What do we mean by negligible and How do you “assess” exposureShould this also include an assessment of intake?Does the susceptibility of the sub-population need to be taken into account in assessing when a route can be considered negligible? 7/6/108TAGS workshop
- 10. 7/6/1010
- 11. 7/6/1011
- 12. An example: Pesticide XPurpose: risk assessment for British populationFood contaminated > ingestionUse of a consumer product (Y) containingOnly concerned with chronic exposureXis non volatile and is not taken up through the skin so ingestion is the only possible routeNot necessary to aggregate over routes7/6/1012TAGS workshop
- 13. 7/6/10TAGS workshop13Define the purpose of the exposure assessmentPurpose to distinguish between pathways/routes? YAEANIgnoring the magnitude of exposure, is there a basis for aggregation across routes?Screening of relative magnitude of routes: is one route more important than others?NYNYNCan we subdivide the population to simplify the assessment?Ignoring the magnitude of exposure, is there a basis for aggregation across sources/ pathways?Screening of relative magnitude of different sources/pathways: is one more important than others?NYYNYSEA
- 14. 7/6/1014
- 15. Pathways for Xcontaminated food > ingestionuse of product Y > skin contamination layer > ingestionuse of product Y > surfaces > ingestionuse of product Y > surfaces > skin contamination layer > ingestionuse of product Y > surfaces > clothing > skin contamination layer > ingestionuse of product Y > clothing > skin contamination layer > ingestion7/6/1015TAGS workshop
- 16. A Simple Exposure Assessment?Two scenarios for exposure to chemical XFor consumers who use the product the presence of trace amounts of chemical in food would make a negligible contribution to their aggregate exposure Simplify the approach into two SEAsone for consumers who use product Y one for the remainder of the populationIt is therefore not necessary to conduct an AEA in this case. 7/6/1016TAGS workshop
- 17. An example revisited : Pesticide XPurpose: risk assessment for British populationFood contaminated > ingestionUse of a consumer product (Y) containing Only concerned with chronic exposureX is non volatileX is taken up through the skin and by ingestionIgnoring the magnitude of exposure aggregation across routes may be necessary7/6/10TAGS workshop17
- 18. 7/6/10TAGS workshop18Define the purpose of the exposure assessmentPurpose to distinguish between pathways/routes? YAEANIgnoring the magnitude of exposure, is there a basis for aggregation across routes?Screening of relative magnitude of routes: is one route more important than others?NYNYNCan we subdivide the population to simplify the assessment?Ignoring the magnitude of exposure, is there a basis for aggregation across sources/ pathways?Screening of relative magnitude of different sources/pathways: is one more important than others?NYYNYSEA