Chemical Toxicology 2010 Safety Manual & Laboratory Safety Chemical Hygiene Plan, p. 71 - 76 May 17, 2011
DEFINITIONS Toxicology – the study of the nature and action of poisons Toxicity – the ability of a chemical substance or compound to produce injury once it reaches a susceptible site in, or on, the body Hazard potential – the probability that injury will occur after consideration of the conditions under which the substance is used
All things are poison, and nothing is without poison; only the dose permits something not to be poisonous. - Paracelsus
ROUTES OF ENTRY • Three main routes: • through the respiratory tract • through the skin • through the digestive tract
Most exposure standards, such as the Threshold Limit Values (TLV's) and Permissible Exposure Limits (PEL's), are based on the inhalation route of exposure. These limits are normally expressed in terms of either parts per million (ppm) or milligrams per cubic meter (mg/m3) concentration in air. If a significant route of exposure for a substance is through skin contact, the MSDS, PEL and/or TLV will have a "skin" notation. Examples of substances where skin absorption may be a significant factor include: pesticides, carbon disulfide, carbon tetrachloride, dioxane, mercury, thallium compounds, xylene and hydrogen cyanide.