Operating Engineers National Hazmat Program 1 Dose and response The reaction is dependent on the amount of the chemical received, but... – Some doses are so small they produce no response – Once the maximum reaction has occurred, increasing the dose doesn ’ t change the reaction

Operating Engineers National Hazmat Program 2 Acute and chronic exposures Acute - sudden, brief – A bee sting Chronic - repeated small doses over time – Smoking cigarettes for years

Operating Engineers National Hazmat Program 3 Acute and chronic effects Acute - lasting hours Chronic - lasting a long time - possibly years

Operating Engineers National Hazmat Program 4 LD 50 and LC 50 These terms derive from laboratory tests on animals – LD 50 is the dose which when swallowed, injected, or applied directly, kills half the test subjects – LC 50 is the concentration of a chemical in a test atmosphere that kills half the test subjects within one hour when inhaled

Operating Engineers National Hazmat Program 5 Good work practices Read the MSDSs – Material Data Safety Sheet Use PPE when required – Personal Protective Equipment Practice good hygiene – Don ’ t eat, drink, smoke, or apply cosmetics around hazardous chemicals – Wash your hands – If showering and changing clothes after your shift is recommended, do so

Dose-Response Curves for Beneficial Substances At very low doses, there is an adverse effect (deficiency), which decreases with increasing dose (homeostasis). At very high doses, an adverse response appears from toxicity. For example, vitamin A can cause liver toxicity and birth defects at high doses and vitamin A deficiency is lethal. toxicity

Toxic Potency AgentLD 50 (mg/kg) Ethyl alcohol10,000 Sodium chloride4,000 BHA/BHT (antioxidants)2,000 Morphine sulfate900 Caffeine200 Nicotine1 Curare0.5 Shellfish toxin0.01 sarin0.001 Botulinum toxin slight moderate high Extremely high (<1 mg/kg)