Hazardous substances can enter the body in four ways: inhalation, ingestion, absorption and injection. Based on the particular chemical, it may enter the body from one or more of these methods.
Inhalation takes chemicals into the nose or mouth, down the windpipe, and into the lungs. Some chemicals become trapped in the lungs. Others exit while exhaling. However, many chemicals can pass from the lungs and into the bloodstream. Gases, fumes, and tiny solid particles are most commonly inhaled.
Ingestion occurs when you swallow something that ends up in the stomach. From the stomach, many chemicals enter the intestines where they can be absorbed into the bloodstream. Tiny solid particles and liquids can be ingested.
Absorption occurs when chemicals contact the skin. From the skin, the chemical can also enter the bloodstream. Liquids and gases can be absorbed through body surfaces.
Injection is when chemicals penetrate the body through a wound, cut, or puncture of the skin. Gases under high pressure can cut skin tissue and inject chemicals into the body.