Toxicology and Chemical Exposure CEE-PUBH 5670 Hazardous Chemical Handling and Safety

Routes of Exposure Inhalation Skin and/or eye absorption Ingestion Injection

Inhalation Often primary route of exposure at hazardous waste sites Water solubility of vapor or gas important determinant of how much inhaled material reaches lung tissue Highly water-soluble gases (ammonia, alcohols, chlorine) dissolve in upper respiratory tract and impact trachea and bronchi Less water soluble gases (i.e. nitrogen dioxide, phosgene) may impact lungs and circulatory system Toxic gases can be colorless and odorless

Skin and Eye Contact and Absorption Contact can be made with solid, liquid, vapor, aerosol, a mist or a fume Skin effect barrier against particulates and large molecular weight chemicals Lipid-soluble chemicals can be readily absorbed through skin Corrosives can destroy skin and eye tissues

Ingestion Deliberate ingestion unlikely Personal habits-chewing gum, biting fingernails, applying cosmetics or lip balm, eating or drinking

Injection Introduction of chemicals directly into bloodstream Puncture wound, open cut

Amount or Concentration High dose level animal studies extrapolated to human toxicity Epidemiology studies follow groups of worker exposed to low concentrations of chemicals

Dose-response relationship As dose (or concentration) increases, the response increases Assume some concentration a chemical will have no adverse effect-not easily demonstrated

Duration and Frequency Duration - length of time of each exposure Frequency - number of exposures

Acute Exposures Single, usually brief, contact with a chemical agent. Acute toxicity refers to the ability of a chemical to cause adverse effects as a result of one-time exposure. Many acute exposures are reversible (e.g. coughing, headache, nausea)

Chronic Exposures Repeated exposure over a prolonged period of time Chronic toxicity is the ability of the chemical to cause adverse effects as the result of repeated exposures May chronic exposures cause irreversible effects (e.g. emphysema, cancer)

Combined Effect of Exposures Both acute and chronic effects

Other factors affecting susceptibility Individual sensitivity due to age, sex, overall physical health, genetic type Multiple chemical exposure

Synergistic effect Potentiation Antagonism

Synergistic effect Two chemicals having an effect greater than additive (ethyl alcohol and carbon tetrachloride)

Potentiation type of synergism where one chemical (usually not toxic itself) has the ability to increase the toxicity of another chemical (isopropyl alcohol and chloroform)

Antagonism when exposure to two chemical produces less toxicity than found when only one of the chemicals is present (e.g-antidotes like chelating agents)

Terminology-toxicity LD 50 (rats) -Dose that kills 50% of the test subjects (rats) exposed (mg/kg) TD-toxic dose LC 50 -Concentration that kills 50% of the test subjects exposed (mg/L or mg/m 3 ) TC-toxic concentration ED-effective dose (pharmaceuticals)

NOAEL (No Observable Adverse Effect Level) Concentration or dose that produces no evidence of toxicity

LOAEL (Lowest Observable Adverse Effect Level) Lowest concentration or dose that produces some evidence of toxicity

Toxicity Rating Slightly toxic, moderately toxic and toxic

Health Hazards Systemic Toxins-specific organs Asphyxiants –Simple: displace oxygen in air –Chemical: substance that interfere with transport or utilization of oxygen Sensitizers-produce allergic reactions in sensitive individuals Irritants-dermal, eye, respiratory tract Carcinogens-substance that cause cancer Mutagens-substances that cause genetic change by damaging genes or chromosomes Teratogens--substances that cause birth defects

Exposure Limits Standards of guidelines developed by various organizations to prevent chemical overexposure to works Based on concept that there is a threshold concentration or dose below which no adverse health effects are observed. Based on historical information from workplace experiences, laboratory animal or human studies, analogy to similar chemicals, or combination

Permissible Exposure Limit (PELs) Established by OSHA in 1971 for nearly 600 materials Maximum average concentration that a worker may be exposed to for 8 hrs a day, 40 hrs a week. Requires amending original law to change

Ceiling Limits When concentration in air cannot exceed a specific maximum concentration at any time during exposure

Short term exposure limts (STELs) Peak concentration that a worker may be exposed to for a short period of time during the workday. Should not exceed 15 minutes and should be followed by 60 min interval without exposure No more than four STEL exposures per workday

Threshold Limit Values (TLVs) American Conf. Of Governmental Industrial Hygenists (ACGIH) provides TLVs for approx. 700 substances Reviewed, updated and published yearly TLE-TWA is analogous to OSHA PEL

Workplace Environmental Exposure Levels (WEELs) Guides developed by American Industrial Hygiene Association for substances that do not have OSHA PELs or ACGIH TLVs. Most are 8 hr TWAs

National Institute for Occupational Safety and Health (NIOSH) Agency within the Dept of Health and Human Services given the responsibility to identify workplace hazards, develop and publish air sampling and analysis method and recommend workplace exposure limits to OSHA. REL-recommended exposure limit based on 10 hr workday and 40 hr workweek IDLH-Immediately Dangerous to Life and Health NIOSH also defines 10% of LEL as an IDLH