Routes of exposure

A hazard only harms you if it reaches your body, so the route matters as much as the chemical. A substance that is dangerous when swallowed may be harmless on intact skin, and the reverse can also be true. Controls should be matched to the likely route.

In most workplaces inhalation is the main concern because vapors, dusts, mists and fumes are easily breathed and pass quickly into the blood through the lungs. Skin absorption is the second major route, and some solvents and pesticides pass through skin in harmful amounts. Eye contact can cause local injury and also absorption. Ingestion usually happens indirectly, through contaminated hands, food or drink. Injection can occur from needle sticks or high-pressure equipment leaks.

The SDS addresses routes in several places. Section 4 describes first aid by route, Section 8 lists controls and protective equipment, and Section 11 gives the likely routes and toxicity data. The GHS acute toxicity categories are set separately for the oral, dermal and inhalation routes.

Routes can combine. A worker may breathe vapor while also absorbing the same chemical through skin, so total dose can exceed what air monitoring alone suggests.