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SAN JOAQUIN DELTA COLLEGE EXPOSURE DESCRIPTION TABLE Exposure Route of TOXIC EFFECTS Category Time Exposure Human Animal TDLo Acute or All except Any Non-Lethal CARO, NEO Chronic inhalation ETA, TER TCLo Acute or Inhalation Any Non-Lethal CARC, NEO Chronic ETA, TER LDLo Acute or All except Death Death Chronic inhalation LD50 Acute All except Not Applicable Death (statistically determined) LCLo Acute or Inhalation Death Death Chronic LC50 Acute Inhalation Not Applicable Death (statistically determined) TABLE VI Effects-It is essential to differentiate between acute and chronic effects of chemicals and acute and chronic exposures Chronic toxicity must be related to chronic illness produced by exposure to chemicals regardless of the duration of such exposure, even an acute exposure may produce a chronic illness, i e, heavy metals and carcinogens Repeated exposure to such chemicals accentuate chronic illness On the other hand, exposure to cyanides or sulfides does not produce chronic illness but instead produces acute poisoning and death Toxic effects may be local or systemic, depending on the area exposed Local exposure affects the nose, eyes, mouth, throat, skin, and various parts of the respiratory and gastrointestinal tracts, absorption does not have to occur With chronic exposure, however, absorption does occur, and the site of damage may be remote from the site of contact In many cases both local and systemic damage occurs Dosage - Dosage is the most important factor in determining whether a given chemical will produce a toxic effect There is a large variation in the toxicity of chemicals, and even water can cause illnesses For comparisons of the toxicities of different chemicals,the median lethal dose(LD50) is usually used as the yardstick and is stated as weight of poison per unit body weight or surface area The median lethal dose is a statistical estimate of the amount of chemical required to kill 50% of a given population of test animals It is useful also to make a comparison of the susceptibility of various animals species regardless of size To be meaningful,the LD50 must specify the experimental conditions, route of administration, species, age, sex, number of doses, and the time of the measurement in days or weeks Other factors may include the route of exposure, i c , ingestion, inhalation, of dermal, type of formulation, temperature, humidity, barometric pressure, physiologic state of the subject, and the possible interaction between two or more administered chemicals Page #7