Toxic Chemical Hazards All chemicals can be toxic

Toxic Chemical Hazards All chemicals can be toxic, but few actually hurt us. WHY? It’s the dose that makes the poison 化 安全概論

Dose-Response Model The higher the dose of a chemical, the more severe the response 化 安全概論

Relative Toxicity Some chemicals are more toxic than others at the same quantity, so toxicity indexes were developed 化 安全概論

LD 50 • Refers to dose fed to an animal population • The lethal dose to 50% of an animal population • Given in mg/kg of body weight(應該報導試驗的 動物) 化 安全概論

LC 50 • Refers to the concentration of chemical in the air inhaled by an animal population • The lethal concentration to 50% of an animal population • Given in mg/m 3 (注意單位) 化 安全概論

LD 50 & LC 50 • Remember that these are lethal doses to animals, not people • Still the best method for relative toxicity 化 安全概論

以劑量言: LD 50 (lethal) > TD 50 (toxic) > ED 50 (effective) > ED 10 化 安全概論

TLV • The Threshold Limit Value (TLV) is a guideline concentration developed by the American Council of Governmental Industrial Hygienists (ACGIH) • TLVs are recommendations and should be used as guidelines for good practices 也就是我國作業環境容許濃度之參考 基準 化 安全概論

TLV • TLVs refer to airborne concentrations of substances • TLVs represent conditions under which it is believed that nearly all workers may be repeatedly exposed to day after day without adverse health effects 化 安全概論

TLV • TLVs are based on available information from: • industrial experience • experimental human studies • experimental animal studies • The amount and nature of the information varies from substance to substance ; consequently, the precision of the estimated TLV is also subject to variation 化 安全概論

TLV-TWA Threshold Limit Value-Time Weighted Average • The time-weighted average concentration for a normal 8 -hour workday and a 40 -hour workweek • Nearly all workers may be repeatedly exposed, day after day, without adverse effect • TWA = 1/8 C(t) dt (t: 0 tw) where tw= worker shift time in hours 化 安全概論

TLV-STEL Threshold Limit Value-Short Term Exposure Limit The concentrations to which workers can be exposed continuously for a short period of time without suffering from: • irritation • chronic or irreversible tissue damage • narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue, or materially reduce work efficiency 化 安全概論

Ceiling Limit The concentration that should not be exceeded during any part of the working exposure 化 安全概論

STEL Short Term Exposure Limit • A 15 minute TWA exposure which should not be exceeded at any time during a workday even if the 8 hour TWA is within the TLV-TWA • Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should not occur more than four times per day 化 安全概論

STEL • There should be at least 60 minutes between successive exposures in this range • Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day • Under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded 化 安全概論

PEL Permissible Exposure Limit • PEL is an exposure limit set by OSHA • Similar to TLVs, the PEL refers to concentrations to which the employee may be exposed • PELs are legally binding 化 安全概論

IDLH Immediately Dangerous to Life or Health Specifically refers to the acute respiratory exposure that poses an immediate threat of loss of life, immediate or delayed irreversible adverse effects on health, or acute eye exposure that would prevent escape from a hazardous atmosphere 化 安全概論

Relative Toxicity The LD 50, LC 50, TLV, PEL, STEL, Ceiling, and IDLH provide a good index of the toxicity of the chemical 化 安全概論

Concentration • The higher the concentration or dose of the chemical, the higher the risk of harmful effects • Nitrogen at 78% concentration in the air is healthy, but at over 85%, it asphyxiates humans 化 安全概論

Concentration Probable Oral Dose for Humans Toxicity Rating Dose For Average Adult Practically nontoxic >15 g/kg more than 1 quart Slightly toxic 5 -15 g/kg between pint and quart Moderately toxic . 5 -5 g/kg between ounce and pint Very toxic 50 -500 mg/kg between tsp. and ounce Extremely toxic 1 -50 mg/kg between 7 drips and tsp. Super toxic <1 mg/kg a taste 化 安全概論

Time of Exposure The dose-response model teaches the toxicity risk increases as: • relative toxicity increases • concentration increases • length of exposure increases 化 安全概論

Effects • Acute • a rapid, sudden exposure • the harmful effects are immediate • Chronic • repeated, small exposures • the harmful effects are delayed • sometimes as long as 40 years • Latency Period • the time between the exposure and the effect 化 安全概論

Probit èProbit = probability unit 是一種表示response-dose 關係的方法，可以畫成直線圖，方便比較。 èP probability = {1/(2 ) 1/2} exp(-u 2/2) du [from Y -5 to - ] 提供P 與probit變數Y間的關係 èY = k 1 + k 2 ln. V; k 1, k 2是參數，V代表劑量dose (caustic factor); Y probit variable; k 1, k 2則視意外 事件之不同而有差別。 化 安全概論

若干常用有機溶劑的毒性 • 確定有害者: benzene, carbon bisulfide, CCl 4, formaldehyde, methyl alcohol, phenol, tetrachloroethane, etc. • 中等危害性: amyl acetate, cumene, butyl alcohol, cycloheptane, nitroethane, toluene, xylent, etc. • 比較無害者: ethyl alcohol, ethyl acetate, ethyl ether, heptane, hexane, petroleum ether, etc. 化 安全概論

ROUTES OF ENTRY How do chemicals enter our bodies to cause harm? 化 安全概論

Routes of Entry Four routes of entry are recognized: • Inhalation 吸入 • Absorption 吸收(皮膚) • Ingestion 食入(消化器官) • Injection 注射 • 劑量過高的結果, 中毒或職業病 化 安全概論

Inhalation is the most common form of occupational exposure to chemicals 化 安全概論

Inhalation • Minimize inhalation of hazardous chemicals through: • good ventilation • use of fume hoods/glove-box • respirator • Always try to engineer out the hazard BEFORE resorting to a respirator 化 安全概論

Inhalation • Respirators can pose additional hazards to the user • Punctured eardrums also provide an inhalation route of entry 化 安全概論

Absorption The most frequently reported occupational injuries are chemical effects to the skin 化 安全概論

Absorption • Not all chemicals are absorbed through the skin: many defat the skin and cause injury • How do we minimize chemical absorption through the skin? • Gloves provide a good barrier when the appropriate glove materials are used 化 安全概論

Ingestion We probably do not eat our lab chemicals so how do we sometimes swallow them? 化 安全概論

Ingestion Minimize the ingestion route of entry by: • NO eating or drinking in the lab • NO smoking in the lab • ALWAYS wash your hands when leaving the lab 化 安全概論

Injection Very few, if any, accidents occur in the laboratory as a result of accidental injection of a chemical filled syringe 化 安全概論

Injection How can this happen? • cleaning up contaminated broken glass • cutting self on contaminated sharps • leak in high pressure hoses • puncturing self with a contaminated syringe 化 安全概論

Injection How can this route of entry be minimized? • use only a broom and dust pan for cleaning up broken glass • dispose of used syringes, do not recap them • wear puncture resistant gloves 化 安全概論

SUMMARY If the toxicity of a chemical is unknown, treat it as toxic 化 安全概論

SUMMARY Use a fume hood or glove box when the chemical could become a vapor or dust 化 安全概論

SUMMARY Always wear the proper personal protective equipment • eye protection • gloves • lab coat 化 安全概論

SUMMARY Change protective garments as required 化 安全概論

SUMMARY Decontaminate before eating, drinking, smoking, or going to the bathroom 化 安全概論

SUMMARY Minimize the time of exposure 化 安全概論

SUMMARY Become familiar with the Standard Operating Procedures for safe handling of toxic materials 化 安全概論

Toxics Knowledge of a chemical’s toxic properties and the correct handling precautions can prevent adverse health effects (e. g. read MSDS) 化 安全概論