Publisher Summary The toxicity of a substance is its capacity to cause injury once inside the body. The main modes of entry of chemicals into the body in industry are inhalation, ingestion and absorption through the skin. Gases, vapors, mists, dusts, fumes and aerosols can be inhaled and they can also affect the skin, eyes and mucous membranes. Ingestion is rare, but possible as a result of poor personal hygiene, subconscious hand-to-mouth contact, or accidents. The skin can be affected directly by contact with the chemicals, even when intact, but its permeability to certain substances also offers a route into the body.