Air And Water Pollution Control (AWPC) Exam 2 Practice

Hazard in environmental risk terms comes from how harmful a substance could be and how much contact people or the environment has with it. Toxicity tells you how severe the harm could be if exposure occurs, while exposure tells you how much contact occurs in the real world. When you multiply these two factors, you get a measure that increases when either the substance is more toxic or the exposure is greater, which is exactly how potential harm is driven in practice. Using only toxicity misses how often or how intensely people are exposed. Using only exposure misses how severe the harm could be if exposure happens. Using dose instead of exposure shifts the focus to the amount that actually gets into or reaches a target, which isn’t the same as the overall contact risk in the environment. An additive combination or mixing dose and toxicity doesn’t capture the way hazard scales with both factors together.