A cumulative risk assessment evaluates the potential for people to be exposed to more than one pesticide at a time from a group that share an identified common mechanism of toxicity. A common mechanism of toxicity is identified when two or more chemicals or other substances cause a common toxic effect(s) by the same, or essentially the same, sequence of major biochemical events. 

Our cumulative assessments approximate people's actual exposures and potential risks resulting from current uses of these pesticides in different parts of the country.

• We consider potential exposures from food, drinking water, and residential sources.
• We incorporate regional exposures from residential and drinking water sources because this is the most appropriate way to account for the considerable variation in potential exposures across the country.

We performed cumulative risk assessments for five groups of pesticides share a common mechanism of toxicity.  Assessment will be conducted for any other common mechanism groups identified in the future.

• Organophosphates (OPs)
• N-methyl carbamates
• Triazines
• Chloroacetanilides
• Pyrethrins / Pyrethroids

We also examined thiocarbamates and dithiocarbamates and determined they do not share a common mechanism of toxicity. 

EPA has guidance for:

• Performing cumulative risk assessment.
• Identifying pesticides chemicals and other substances that have a common mechanism of toxicity.
• Framework for Screening Analysis.