1 Toxicological effects - Irritants Irritation Inflammation or aggravation of tissue from contact Influenced by solubility Primary or secondary

2 Toxicological effects - Irritants Primary irritant A material that exerts its effect at the site of action with little or no systemic effects Acids, alkalis, etc. that produce burns on the skin but produce no other systemic effects

3 Toxicological effects - Irritants Secondary irritant A material that still exerts an effect at the site of action but also has significant systemic effects E.g. aromatic hydrocarbons: phenol causes skin irritation but systemically it poisons the body and can cause death

4 Toxicological effects - Asphyxiants Asphyxiants interfere with oxygenation Anoxia – no oxygen in the blood: 3-5 min brain damage and death Hypoxia – low levels of oxygen in the blood: can lead to brain damage or death Simple Exert effect by diluting or displacing oxygen

5 Toxicological effects - Asphyxiants Chemical asphyxiants disrupt oxygen metabolism or the body’s ability to control respiration Effects O 2 metabolism in the cell Hydrogen sulfide (H 2 S) paralyzes the respiratory center of the brain and stops breathing

6 Basis for workplace standards Animal data Appropriate animal models Human epidemiological data Descriptive studies Retrospective studies Prospective studies

7 Workplace exposure limits For any agent or condition, there is a level of exposure (concentration and time dependent) for which the effects are acceptable. Exposure limits are set at such levels

8 ACGIH TLVs American Conference of Governmental Industrial Hygiene (ACGIH) Threshold Limit Value (TLV) A time-weight average (TWA) conc. for a normal 8-hr workday and a 40-hr. work week, to which nearly all workers may be repeatedly exposed, day after day without adverse effect

9 ACGIH TLVs TLV-STEL (short-term exposure limit) A 15 min. TWA exposure which should not be exceeded at any time during a workday even if the 8-hr TWA is within the TLV. Exposures < 15 min; not more than 4 x a day and be at least 60 min apart

10 ACGIH TLVs TLV-C (ceiling) The conc. that should not be exceeded during any part of the working exposure