TOXIC CHEMICALS. Supawan Tantayanon Department of Chemistry, Faculty of Science Chulalongkorn University

Transcription

1 TOXIC CHEMICALS Supawan Tantayanon Department of Chemistry, Faculty of Science Chulalongkorn University

2 Toxic Chemicals Any chemical when ingested, inhaled, or absorbed, or when applied to, injected into or developed within the body, in relatively small amounts, by its chemical action may cause damage to structure or disturbance to function

3 Toxic Chemicals Toxic substances may cause injury by damaging biological structure and/or disturbing biological function

4 SOME COMMON CHEMICALS CLASSIFIED BY TYPE OF DAMAGE Damage to structure Sulfuric acid, 50% sodium hydroxide, and other corrosive materials cause burning and irritation Disturbance of Function Carbon monoxide decreases the ability of hemoglobin to transport oxygen to cell Parathion is a cholinestearase inhibitor; thus it blocks the transfer of nerve impulses. Both Effects Chlorine when inhaled damages the lungs; this damage can inhibit the oxygen exchange in the lungs

5 Damage can be acute and/or chronic BENZENE Acute Irritation, aromatic hydrocarbon poisoning chronic Anemia, leukemia, death

6 Damage by two different compounds CH 3 Benzene Toluene Acute 2 2 Chronic 3 2 TWA 10 ppm 100 ppm TWA = Time Weighted Average

7 What are some of the parameters which affect toxicity? Mode of entry Physical condition Dose Duration Sensitivity Combined effects Stress Others--sex, race, temperature, altitude

8 TWA = Time Weighted Average TWA = n i = 1 T i C i T total = Exposure time 1 Concentration 1 + Exposure Concentration +... time 2 2 Total time worked per shift

9 TLV = Threshold Limit Value is an estimate of the average safe toxicant concentration that can be tolerated on the repetitive basis, usually an eight-hour period on a day-to-day basis should not be applied literally, but rather used as general guidelines TLV - TWA (Time Weighted Average) TLV - STEL (Short Term Exposure Limit) TLV - C (Ceiling)

10 Toxic and normal levels of chemicals in the blood (Unit: milligrams% ) Chemical Normal Level Toxic level Acetone 0 30 Acetylsalicylic Acid (Aspirin) 5 40 Arsenic < Benzene 0 any trace Bromide Carbon Monoxide 1 30 Cyanide Ethanol Fluoride < Lead < Oxalic Acid

11 LD 50 (LD = Lethal Dose, 50% Kill) is the dose which, when administered to test animals, kills half of them expressed in mg of toxicant per kilogram of body mass, and the test route is given (but not inhalation) For example LD 50 (oral, rat) of NaCN = 6 mg/kg How does the LD 50 for rats relate to man? By extrapolation, assuming a LD 50 of 6 mg/kg for both rats and humans 6 x 75 = 450 mg

12 LC 50 (Lethal Concentration, 50% Kill) is that concentration of a toxicant in air or other suitable vehicle, which, when administered to test animals for a definite time period, kills 50% of them. is given in parts per million (ppm) for that time of period For example LC 50 (inhalation, rat) of HCN = 544 ppm/5 min.

13 What are the common modes of entry for toxic chemicals? SKIN (Absorption) Sweat Glands Hair Follicles Open Wounds Rapid distribution of toxicants is facilitated by the lymphatic system.

14 NOSE (Inhalation) For most chemicals in the form of vapors,gases, mists or particulates Once inhaled, chemicals are either exhaled or deposited in the respiratory tract If deposited, damage can occur through direct contact with tissue or diffusion into the blood through the lung blood interface

15 NOSE (Inhalation) Upon contact with tissue, health effects ranging from simple irritation to severe tissue destruction Substances absorbed into the blood system are circulated and distributed to organs which are sensitive to the toxic chemical and health effect can then occur.

16 MOUTH (Ingestion) Since only minute amounts of toxicants can be ingested by swallowing contaminated air, the primary routes are purposeful or accidental ingestion of copious amounts of the toxicants

17 Injection The equivalent of purposeful injection of toxicants can occur through mechanical injury with contaminated glass or metal--a cut.

18 How are the physical properties and toxicity of chemicals related? Relative hazards A sealed container of HCN represents less hazard than an open vessel of benzene. Physical properties A substance with a lower boiling point is obviously potentially more contaminating than one boiling at higher temperature.

19 How about long-term exposure and delayed responses Carcinogens induce a malignant tumor in man after a reasonable exposure. Mutagens affect the genetic system of the exposed person which may cause hereditary changes in chromosomes. Teratogens interfere with the normal development of the fetus without inducing damage to the mother or killing the fetus which is not hereditary..

20 What are the proper preventive measures 1. Treat it as though it is toxic 2. Cover exposed areas of skin 3. Use a respirator or gas mask, as appropriate 4. Use care in handling contaminated glass ware and metal 5. Change protective garments as required 6. Keep food and cigarettes out of the lab 7. Do not use glassware for eating and drinking

21 What are the proper preventive measures 8. Keep antidotes for common toxicants on hand 9. Alert medical department as to what toxicants are being used, so they can be prepared. 10. Get periodic physical examinations. 11. Train all personnel thoroughly, including the toxicology of their work, where to find data, how to store and handle each substance, and what to do in the event of toxic poisoning.