Occupational Health and Safety

What is Epidemiology?

study of the distribution, determinants, and control of health-related states or events in populations

Who was Dr John Snow?

one of the founders of modern epidemiology and early germ theory; traced source of an 1854 cholera outbreak in London's Soho at the Broad Street public water pump

What is cholera?

acute bacterial infection caused by bacterium Vibrio cholerae; spread through water or food

Why are epidemiological studies difficult?

small sample sizes, variability in subjects, inability to test humans in a controlled environment, long latency periods, poor data

Legionnaires Disease

From July 21 to July 24, 1976, more than 2,000 members of the Pennsylvania American Legion attended an event at Bellevue Stratford Hotel in Philadelphia; Dr. Sidney Freidman treated several patients in the days following and realized they had pneumonia

Bacteria that caused Legionnaires disease

Bacteria found in aquatic environments, inhaled from water droplets in air (from showers, hot tubs, AC systems, swimming pools, and fountains)

Measures used in epidemiology

counts, ratios, proportions

Count

simplest measure; the number of individuals who meet a case definition

Ratio

compares two quantities, where the numerator is not included in the denominator

Proportion

compares a part to the whole, where the numerator is included in the denominator

Calculate death per 100k

mortality rate = (Number of deaths from a specific cause / Estimated mid-year population) x 100,000

Epidemiological triangle

agent, host, environment

Portals of entry

absorption, ingestion, injection, inhalation

Cohort study

(in occupational epidemiology) tracks groups of workers over time to assess how workplace exposures, such as chemicals or noise, are linked to health outcomes like chronic diseases or cancer

Confounding

distortion of the measure of an exposure's effect on an outcome due to association of the exposure with other factors influencing the outcome

Toxicology

science of poisons; comes from Greek word toxikon, meaning poison for arrows

Toxicity

the degree to which a substance can harm humans or animals

Toxicants

anthropogenic toxic substances

Toxin

organic toxic substance

Dose

total amount of a substance that enters the body during a specific exposure event

LD50

the amount of a substance it takes to kill 50% of a specific population

Threshold

lowest dose at which a particular response may occur

Latency

(occupational exposure) time between initial exposure to a harmful agent and manifestation of a disease or health effect

Additive chemical effect

combined effect is worse than the sum of individual effects; e.g., asbestos + smoking

Synergistic chemical effect

combined effect is worse than the sum of individual effects; e.g., asbestos + smoking

Antagonistic chemical reaction

combined effect is less than the sum of individual effects; one chemical mitigates the effect of another

Threshold Limit Value (TLV)

concentration of a chemical in air to which nearly all healthy adult workers can be exposed daily over a working lifetime without adverse effects (recommendation, not law)

Permissible Exposure Limits (PELs)

legally enforceable workplace exposure limit for chemicals set by OSHA; maximum concentration workers can be exposed to over a specific time without adverse effects (law)

Bhopal India Chemical Disaster

December 3, 1984: methyl isocyanate (MIC) leak at Union Carbide pesticide plant in Bhopal, India; thousands of deaths and lasting health effects for hundreds of thousands

Methyl Isocyanate

primarily used as a chemical intermediate in pesticide production, also used for polyurethane foams and plastics

2023 Train Derailment

February 3, 2023: Norfolk Southern freight train derailed in East Palestine, Ohio; affected cars contained vinyl chloride, ethylene glycol, ethylhexyl acrylate, butyl acrylate, and isobutylene

Common Workplace Gases

carbon monoxide, hydrogen sulfide, ammonia, and chlorine

Industrial Solvents / Volatile Organic Compounds (VOC)

chemicals that easily evaporate into the air, such as benzene, trichloroethylene, and toluene

Heavy Metals

lead, mercury, arsenic, cadmium

Dangers of Heavy Metals

exposure through inhalation, ingestion, or skin contact; can cause organ damage, cancer, neurological problems

Mad Hatters Disease

neurological damage in hat factory workers from ingesting small amounts of mercury while crimping hats

Rubber, Petroleum, and Fossil Fuel Based Products

refining crude oil into fuels (gasoline, heating oil, diesel) and petrochemical feedstocks for plastics, chemicals, and synthetic rubber

Persistent Organic Pollutants (POPs)

carbon-based chemicals that persist in the environment, travel long distances, and accumulate in the food chain; e.g., DDT, PCBs, dioxins

Pesticides

chemicals or biological agents used to kill or control pests, including insects, weeds, fungi, rodents, and other organisms

Herbicides

kills weeds

Insecticides

kills insects

Fungicides

kills mold, fungi, mildew

Rodenticides

kills rodents

Rachel Carson

marine biologist and author who raised concerns about DDT

Osprey Population Decline on Cape Cod

DDT weakened osprey eggshells, causing eggs to crush when sat on

PCBs

polychlorinated biphenyls

Take Home Exposure

hazardous substances from a workplace brought into the household, affecting the worker constantly

PFAS

per- and polyfluoroalkyl substances

Diacetyl

chemical compound added to create a buttery flavor

Formaldehyde

preservative and disinfectant that is a known carcinogen