Name the three main routes of exposure to toxic substances.

The three main routes of exposure to toxic substances are inhalation, ingestion, and dermal contact.

Inhalation refers to breathing in airborne toxins, which can quickly enter the bloodstream through the lungs and affect the entire body. This route is particularly significant for gases, vapors, and aerosols.

Ingestion involves swallowing toxic substances, which pass through the digestive system and can lead to systemic effects depending on the substance and the amount consumed. This route is often associated with chemicals in food, beverages, and improperly stored substances.

Dermal contact occurs when toxic substances come into contact with the skin, which can lead to absorption through the skin layers. Some chemicals can penetrate the skin barrier, potentially resulting in localized or systemic toxicity.

The other choices do not accurately represent the primary routes of exposure. While absorption can occur through the skin, it's not commonly listed as a main route of exposure by itself. Similarly, diffusion and filtration are more specific mechanisms that don't encompass the broad ways in which a body can be exposed to toxins. Lastly, while injection is a valid route, it is not one of the primary routes of environmental exposure like inhalation, ingestion, and dermal contact.