Basic principles regarding chemical hazards Introduction Chemicals may exert either acute or chronic effects on workers. The effects exerted by a substance may also be influenced by the presence of other chemicals and physical agents or by an individual's use of tobacco, alcohol, or drugs. The exposure concentration of a substance is the mass per unit volume of air to which a worker is exposed. The exposure dose is the amount of a substance that actually enters the body during the period of exposure. The substance continues to be present in the body until it is metabolized or eliminated.
Some substances can also damage the skin or eyes directly without being absorbed.
Not all substances can enter the body through all routes. Inorganic lead, for example, can be inhaled or swallowed, but it does not penetrate the skin. Sometimes a chemical substance can enter through more than one route. Asbestos, for example, can be swallowed or inhaled, but the latter route appears to be more hazardous. The physical properties of a chemical or physical agent include such characteristics as vapor pressure, solubility in water and organic solvents, boiling point, melting point, molecular weight, specific gravity, and morphology.