THERMAL STRESS …..A DISCUSSION OF THE HEALTH HAZARDS ASSOCIATED WITH TEMPERATURE/HUMIDITY EXTREMES

Overview n Sources of heat –High air temperatures –Radiant heat sources –High humidity –Direct physical contact with hot objects –Strenuous physical activities n Sources of cold –Low air temperatures –Wet and windy environments –Direct physical contact with cold objects

Industries n Iron and steel foundries n Brick-firing plant n Ceramic plants n Glass products facilities n Rubber products factories n Electrical utilities n Bakeries n Commercial kitchens n Laundries n Food canneries n Chemical plants n Mining sites* n Smelters n Steam tunnels n Construction sites* n Asbestos removal n Hazardous waste site activities* * cold or heat exposure

Key Definitions n Heat – a measure of energy n Metabolism - the system of chemical activities by which a living thing gets power (energy) from other things, such as food n Conduction- the transfer of heat between materials that contact each other n Convection- the transfer of heat in a moving fluid n Radiation - the transfer of heat energy through space n Evaporative cooling- takes place when sweat evaporates from the skin n Hypothermia – systematic effect of cold stress; reduced body temperature n Hyperthermia – systematic effect of heat stress; increase in core body temperature

Causal Factors n Primary: –Environment/climatic conditions –Clothing –Work Demands n Secondary –Age –Weight –Degree of physical fitness –Degree of acclimatization –Use of alcohol or drugs –Medical conditions –Prior heat/cold injuries

Responses of Humans to Heat n Increased flow of blood n Sweating n Illnesses/disorders n Acclimatization to heat n Susceptibility to diseases

Signs and Symptoms Heat Stress n Markedly raised temperature of about 40°C (104°F) or more. n Headache, nausea, vomiting; loss of appetite n Fast heart rate (tachycardia); fast breathing n Red skin; skin may feel hot to touch n Profuse sweating which eventually leads to an absence of sweating n Chills and shivering is possible n Confusion; dizziness; fainting; convulsions; coma/unconsciousness n Temporary Blindness is possible Cold Stress n Dry, cold skin n Shivering, but only during the early stages n Slow pulse; slow breathing n Drowsiness, which can lapse into coma.

Metabolic Expenditures n sleeping n desk work n light machine work n moderate assembly work n lifting, manual handling n pick & shovel work

Activities Within Metabolic Rate Categories CategoryExample Activities RestingSitting quietly; sitting with moderate arm movements LightSitting with moderate arm and leg movements; standing with light work at machine; using table saw, some walking about ModerateScrubbing in a standing position; walking with moderate lifting or pushing or carrying 3 kg load HeavySawing by hand; shoveling dry sand; heavy assembly work on a non-continuous basis; intermittent heavy lifting with pushing or pulling (pick-and-shovel work) Very HeavyShoveling wet sand

Heat-Related Illnesses n Heat stroke n Heat exhaustion n Heat cramps n Heat collapse n Heat rash n Heat fatigue

Standards… n OSHA General Duty Clause n ACGIH – 100.4°F/96.8°F

Ways to reduce heat stress n Engineering controls –Ventilation –Shielding –Cooling fans, etc. n Work practices –Drinking plenty of water –Training n Move to cooler place n Reduce work pace or work load n Removing or loosening clothing n Acclimate

Ways to reduce cold stress n Engineering controls –Heating –Shielding (from wind) n Work practices –Training n Move to warmer place; avoid winds and wet environments n Clothing –Adequate insulating dry clothing –Protect extremities

Summary of Identification n Is the environment recognized as being hot/cold, is protective clothing required, or are work demands high (in a hot environment)? n Are worker behaviors indicative of attempts to reduce heat or cold stress, is morale low or absenteeism high, or are people making mistakes or getting hurt? n Do medical records show a pattern of the symptoms of exposure? n Are body temperatures (or in the case of heat stress- heart rate or sweat losses high) on a sample of workers?