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😷Environmental and Occupational Health

Major Occupational Hazards

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Why This Matters

Understanding occupational hazards isn't just about memorizing a list of workplace dangers—it's about recognizing the mechanisms of harm and the hierarchy of controls that form the foundation of environmental and occupational health practice. You're being tested on your ability to identify exposure pathways, dose-response relationships, and prevention strategies that protect worker populations. These concepts connect directly to broader public health principles like risk assessment, epidemiological surveillance, and health policy development.

Each hazard category demonstrates different principles: some operate through direct tissue damage, others through cumulative exposure, and still others through systemic physiological stress. When you encounter exam questions, don't just recall that "chemicals are dangerous"—know why certain exposures cause specific health outcomes and how the hierarchy of controls (elimination, substitution, engineering controls, administrative controls, PPE) applies differently to each hazard type. This conceptual understanding will serve you far better than rote memorization.


Direct Agent Hazards

These hazards involve exposure to specific harmful agents—chemical, biological, or radiological—that enter the body through defined routes and cause predictable health effects. The key principle here is the exposure pathway: inhalation, ingestion, dermal contact, or injection.

Chemical Hazards

  • Routes of exposure determine health outcomes—inhalation affects the respiratory system, dermal contact causes skin disorders, and ingestion leads to systemic toxicity
  • Dose-response relationships govern severity; acute high-dose exposures cause immediate effects while chronic low-dose exposures lead to conditions like occupational cancers and organ damage
  • Safety Data Sheets (SDS) and proper labeling are legally mandated controls that inform workers about hazard classification, first aid measures, and PPE requirements

Biological Hazards

  • Pathogen transmission occurs through direct contact, airborne droplets, bloodborne exposure, or vector-borne routes depending on the infectious agent
  • High-risk occupations include healthcare, agriculture, veterinary work, and laboratory settings where contact with bacteria, viruses, fungi, and parasites is routine
  • Prevention hierarchy prioritizes engineering controls (biosafety cabinets, ventilation) over PPE, with vaccinations serving as a critical administrative control

Radiation Hazards

  • Ionizing radiation (X-rays, gamma rays, radioactive materials) causes DNA damage and increases cancer risk through cumulative exposure measured in sieverts or rem
  • Non-ionizing radiation (UV light, lasers, radiofrequency) causes thermal tissue damage and specific conditions like cataracts and skin cancer
  • ALARA principle (As Low As Reasonably Achievable) guides exposure limits through time, distance, and shielding controls

Compare: Chemical hazards vs. biological hazards—both involve agent exposure and similar routes of entry, but biological agents can replicate and spread person-to-person while chemical exposures are dose-dependent without transmission. FRQs often ask you to design control strategies for each; remember that biological hazards uniquely benefit from vaccination programs.


Energy Transfer Hazards

These hazards cause harm through the transfer of physical energy to the body—whether mechanical, electrical, thermal, or acoustic. The underlying principle is that uncontrolled energy release causes acute traumatic injury.

Mechanical Hazards

  • Unguarded machinery with moving parts, pinch points, and sharp edges causes traumatic injuries including lacerations, crush injuries, and amputations
  • Lockout/tagout (LOTO) procedures are OSHA-mandated controls that prevent unexpected equipment energization during maintenance—a critical exam concept
  • Machine guarding represents engineering controls that physically separate workers from hazard zones without relying on behavior change

Electrical Hazards

  • Current pathway through the body determines injury severity; current passing through the heart causes ventricular fibrillation at exposures as low as 100 milliamps
  • Common causes include faulty wiring, improper grounding, overloaded circuits, and working near energized power lines
  • Ground fault circuit interrupters (GFCIs) and proper lockout procedures are primary engineering and administrative controls

Fire and Explosion Hazards

  • Fire triangle concept—fuel, oxygen, and ignition source must all be present; removing any element prevents combustion
  • Flammable material classification determines storage requirements, with flash point and lower explosive limit (LEL) as key hazard parameters
  • Emergency action plans including evacuation routes, fire suppression systems, and regular drills are required administrative controls

Compare: Mechanical hazards vs. electrical hazards—both involve energy transfer causing acute injury, but mechanical hazards are visible and can be physically guarded while electrical hazards are invisible and require specialized detection equipment. If asked about hierarchy of controls, mechanical hazards are more amenable to engineering solutions.


Environmental Condition Hazards

These hazards arise from the physical work environment itself rather than specific agents or energy sources. The principle here is that ambient conditions outside physiological tolerance ranges cause cumulative harm.

Physical Hazards

  • Noise-induced hearing loss (NIHL) is irreversible and occurs at sustained exposures above 85 decibels; it's one of the most common occupational diseases worldwide
  • Thermal stress includes both heat-related illness (heat stroke, exhaustion) and cold-related conditions (hypothermia, frostbite), governed by wet bulb globe temperature (WBGT) measurements
  • Whole-body and hand-arm vibration causes conditions like Raynaud's phenomenon and musculoskeletal disorders through chronic exposure

Confined Space Hazards

  • Atmospheric hazards include oxygen deficiency (below 19.5%), oxygen enrichment, toxic gases, and flammable atmospheres—the leading cause of confined space fatalities
  • Permit-required confined spaces mandate atmospheric testing, continuous monitoring, ventilation, and standby rescue personnel before entry
  • Engulfment and entrapment risks exist in spaces containing loose materials like grain silos, requiring specialized rescue training and equipment

Compare: Physical hazards vs. confined space hazards—both involve environmental conditions, but physical hazards typically cause gradual cumulative damage while confined spaces can cause immediate fatalities. Confined space entry requires specific permit procedures that don't apply to general physical hazard controls.


Cumulative Stress Hazards

These hazards cause harm through repeated exposure or sustained strain over time rather than single acute events. The mechanism involves tissue microtrauma, physiological adaptation failure, or psychological stress accumulation.

Ergonomic Hazards

  • Musculoskeletal disorders (MSDs) including carpal tunnel syndrome, tendinitis, and low back pain result from repetitive motion, awkward postures, forceful exertions, and contact stress
  • Risk factors are cumulative—frequency, duration, and intensity of exposure combine to determine injury probability
  • Ergonomic interventions follow the hierarchy: redesign tasks and tools (engineering) before implementing job rotation and rest breaks (administrative)

Psychosocial Hazards

  • Workplace stressors include high job demands, low control, effort-reward imbalance, and poor social support—factors measured by validated instruments like the Job Content Questionnaire
  • Health outcomes extend beyond mental health to include cardiovascular disease, immune dysfunction, and increased injury rates through stress-mediated pathways
  • Organizational interventions addressing workload, autonomy, and workplace culture are more effective than individual-level programs like Employee Assistance Programs (EAPs)

Compare: Ergonomic hazards vs. psychosocial hazards—both involve cumulative exposure and chronic health outcomes, but ergonomic hazards have clearer dose-response relationships and more established engineering controls. Psychosocial hazards require organizational-level interventions that are harder to implement and evaluate. Both are increasingly recognized as major contributors to occupational disease burden.


Quick Reference Table

ConceptBest Examples
Agent-based exposure pathwaysChemical hazards, biological hazards, radiation hazards
Acute traumatic injuryMechanical hazards, electrical hazards, fire/explosion hazards
Cumulative/chronic exposureNoise (physical), ergonomic hazards, radiation hazards
Hierarchy of controls applicationMechanical (guarding), chemical (substitution), ergonomic (workstation design)
Permit-required proceduresConfined spaces, lockout/tagout for mechanical/electrical
Organizational-level interventionsPsychosocial hazards, ergonomic hazards
Legally mandated documentationSDS for chemicals, permits for confined spaces, OSHA logs for injuries
Irreversible health outcomesNIHL, occupational cancers, amputations

Self-Check Questions

  1. Which two hazard categories share the characteristic of causing harm through cumulative microtrauma rather than single acute events, and how do their control strategies differ?

  2. A worker develops chronic kidney disease after years of occupational exposure. Which hazard category is most likely responsible, and what exposure pathway would you investigate first?

  3. Compare and contrast the control strategies for biological hazards versus chemical hazards—what unique prevention measure applies to biological hazards that has no equivalent for chemical exposures?

  4. An FRQ asks you to design a safety program for a manufacturing facility. Using the hierarchy of controls, explain why machine guarding (for mechanical hazards) is preferred over training workers to stay away from moving parts.

  5. Which three hazard categories can cause immediate fatalities from a single exposure event, and what common principle connects their emergency response procedures?