Describe the four main routes by which hazardous substances can enter the body and their effects.

1. Inhalation: Hazardous substances can enter the body through inhalation, where they are breathed in through the nose or mouth and absorbed into the lungs. This route is common in occupational settings where workers are exposed to fumes, gases, dust, or vapors. The effects of inhalation exposure can range from irritation of the respiratory tract to more serious conditions such as lung damage, respiratory diseases, and even cancer.

2. Ingestion: Hazardous substances can enter the body through ingestion, where they are swallowed and absorbed through the digestive system. This route of exposure can occur through contaminated food or water, or through accidental ingestion of chemicals. The effects of ingestion exposure can include gastrointestinal irritation, nausea, vomiting, and in severe cases, organ damage or poisoning.

3. Dermal contact: Hazardous substances can enter the body through dermal contact, where they come into direct contact with the skin and are absorbed through the skin barrier. This route of exposure is common in industries where workers handle chemicals or other hazardous materials. The effects of dermal exposure can range from skin irritation, rashes, and burns to more serious conditions such as dermatitis, allergic reactions, and systemic toxicity.

4. Injection: Hazardous substances can enter the body through injection, where they are introduced directly into the bloodstream through a puncture wound or injection site. This route of exposure can occur through needle sticks, accidental cuts, or other injuries that break the skin barrier. The effects of injection exposure can be immediate and severe, leading to rapid absorption of the substance and potentially causing systemic toxicity, organ damage, or even death.