What is the equation for risk / how is risk expressed?

Study for the Ontario Pesticide Training and Certification CORE Test. Prepare with multiple-choice questions, get hints and explanations. Ensure readiness for your certification!

The main idea is that risk from a pesticide comes from two factors: how toxic the chemical is and how much exposure people have to it. The risk is proportional to both, so multiplying toxicity by exposure gives a sensible measure: if either factor is zero, there’s no risk; as either factor increases, the risk grows.

This is why the product form is best. If you added the two factors, you could get a nonzero risk even when there’s no exposure (which doesn’t make sense—no exposure means no risk). If you subtracted, you could end up with negative risk, which isn’t meaningful. Time is part of exposure, but the simplest way to express risk is using the toxic potency times the amount of exposure, capturing how harm potential and contact frequency/duration together drive overall risk.

In practice, a highly toxic pesticide with minimal exposure can pose less risk than a less toxic one with substantial exposure, and increasing exposure or greater toxicity both raise risk in proportion to each other.