Aggregate / Cumulative
What is Aggregate assessment?
Aggregate risk assessments evaluate exposure to a single chemical from all possible exposure routes [oral (dietary and incidental), dermal, inhalation] and sources (dietary, water, residential).
What is Cumulative assessment?
Cumulative risk assessments evaluate exposure to multiple chemicals from all possible sources that act through a similar mode of action to produce a common toxic effect.
What are methods for aggregating exposure?
Aggregate risk can be calculated using two approaches described by the EPA’s Office of Pesticide Programs (OPP) in their 2001 Guidance document (General Principles for Performing Aggregate Exposure and Risk Assessments). These approaches are:
- the Total Margin of Exposure (MOE) approach
- the Aggregate Risk Index (ARI) approach
The Total MOE approach is the preferred method for aggregating risk when the uncertainty factors for the different routes of exposure (oral, dermal or inhalation) are identical. The ARI approach is used when multiple MOEs must be aggregated but different uncertainty factors have been applied to each individual MOE. All of these aggregate calculations will be implemented in CARES NG. The choice of the aggregation method will be the user’s responsibility; no rules for deciding the appropriate aggregation method will be implemented in the CARES NG platform.
What are methods for calculating the cumulative exposure?
Cumulative risk can be calculated using the following approaches:
- the Cumulative Margin of Exposure (MOE) approach
- the Cumulative Risk Index (CRI) approach
- the Hazard Index (HI) approach.
The above approaches are calculated over the Relative Potency Factor (RPF) of each chemical. The RPFs are calculated by dividing the reference dose of the Index Chemical by the reference dose of all of the other chemicals. Once a group of chemicals with a common mode of action is selected in the CARES NG platform, the user will be required to identify an Index Chemical from the set. The purpose of the Index Chemical is to provide a point of reference from which the toxic potencies for all of the chemicals within the group can be standardized.
What toxicity information is used in CARES NG?
Any appropriate benchmark of toxicity (point of departure) selected by the risk assessor such as the no observed effect level (NOEL), the no observed adverse effect level (NOAEL), or the effective dose needed to produce a 10% response (ED10) can be used in CARES NG. Together with the appropriate point of departure, CARES NG requires the following toxicology data for each chemical under analysis:
- the uncertainty factor
- the within-body decay factor (only for Within-day assessment)
- the factor to calculate the cancer risk