Environmental Health Hazards

Why This Matters

Environmental health hazards represent one of the most significant intersections between human activity and public health outcomes—and you're being tested on understanding these connections. These hazards demonstrate core course concepts like exposure pathways, dose-response relationships, vulnerable populations, and the social determinants of health. When you understand how pollutants move through air, water, soil, and food chains to affect human bodies, you're grasping the fundamental mechanisms that drive public health interventions and policy decisions.

The items in this guide aren't random threats to memorize—they're organized by how they reach you and what systems they disrupt. Whether it's particulate matter entering your lungs or endocrine disruptors mimicking hormones, each hazard follows predictable pathways with documented health outcomes. Don't just memorize facts about individual hazards; know what exposure route, mechanism of harm, and prevention strategy each one illustrates. That's what separates a strong exam response from a weak one.

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Atmospheric and Airborne Hazards

These hazards share a common exposure route: inhalation. Once airborne pollutants enter the respiratory system, they can trigger local inflammation or enter the bloodstream, causing systemic effects throughout the body.

Air Pollution

• Particulate matter (PM), nitrogen oxides (NOx), and sulfur dioxide ($SO_2$) are the major pollutants—PM2.5 particles are small enough to penetrate deep into lung tissue
• Sources include vehicle emissions, industrial processes, and fossil fuel combustion—understanding source attribution is key for policy questions
• Health outcomes span respiratory diseases, cardiovascular problems, and premature death—air pollution is a leading environmental cause of mortality worldwide

Indoor Air Quality

• Volatile organic compounds (VOCs), mold, and dust are primary indoor pollutants—often at concentrations 2-5 times higher than outdoor levels
• Poor ventilation amplifies exposure risk—modern energy-efficient buildings can trap pollutants without adequate air exchange
• Health effects include respiratory issues, allergies, and "sick building syndrome"—particularly relevant for vulnerable populations who spend most time indoors

Noise Pollution

• Generated by traffic, industrial activities, and urban development—measured in decibels, with sustained exposure above 70 dB causing harm
• Physiological effects include hearing loss, sleep disturbances, and chronic stress activation—triggers the body's fight-or-flight response
• Linked to cardiovascular disease and reduced quality of life—an often-overlooked environmental health factor on exams

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Water and Soil Contamination

These hazards demonstrate how pollutants move through environmental media and bioaccumulate in food chains. The key concept here is persistence—many contaminants don't break down and concentrate as they move up trophic levels.

Water Contamination

• Sources include industrial discharge, agricultural runoff, and sewage leaks—point source vs. non-point source pollution is a common exam distinction
• Contaminants range from pathogens to heavy metals to pesticides—each with different health outcomes and treatment requirements
• Health effects include gastrointestinal diseases, neurological disorders, and developmental problems—waterborne disease remains a leading cause of death globally

Soil Pollution

• Results from pesticides, fertilizers, and improper waste disposal—contaminants can persist in soil for decades
• Key pollutants include heavy metals, hydrocarbons, and persistent organic pollutants (POPs)—these bioaccumulate in crops and livestock
• Affects food safety, ecosystem health, and land usability—connects environmental degradation to food security

Heavy Metal Pollution

• Lead, mercury, and cadmium are the most commonly tested heavy metals—each has distinct exposure pathways and target organs
• Sources include industrial processes, mining, and improper e-waste disposal—legacy contamination from historical practices remains a major issue
• Causes developmental delays, cognitive impairment, and organ damage—children are especially vulnerable due to developing nervous systems

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Chemical and Toxic Exposures

These hazards operate through specific biochemical mechanisms—disrupting cellular processes, mimicking hormones, or damaging DNA. Understanding the mechanism of harm helps predict which populations are most vulnerable.

Chemical Hazards

• Include industrial chemicals, solvents, and environmental pollutants—exposure can occur through inhalation, ingestion, or skin contact
• Health effects range from acute toxicity to chronic conditions including cancer—dose and duration determine severity
• Regulatory frameworks like OSHA and EPA standards exist to set exposure limits—know that regulation is the primary prevention strategy

Pesticide Exposure

• Occurs through agricultural application, residential use, and contaminated food/water—farmworkers and rural communities face highest exposure
• Linked to neurological disorders, cancers, and reproductive problems—organophosphates inhibit acetylcholinesterase, a key enzyme
• Integrated pest management (IPM) reduces reliance on chemical pesticides—represents a harm reduction approach

Endocrine Disruptors

• Chemicals that mimic or block hormones—found in plastics (BPA), pesticides, and personal care products
• Interfere with reproductive development, metabolism, and growth—effects may appear at very low doses, challenging traditional toxicology
• Particularly harmful during critical developmental windows—fetal exposure and early childhood are highest-risk periods

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Biological and Radiation Hazards

These hazards involve either living organisms or energy that damages cells directly. The key concept is that exposure doesn't always cause immediate symptoms—latency periods can span years or decades.

Biological Hazards

• Include pathogens, allergens, and toxins from living organisms—bacteria, viruses, fungi, and parasites all qualify
• Transmission routes include direct contact, airborne, waterborne, and vector-borne—understanding transmission informs prevention
• Central to public health surveillance and outbreak response—epidemiological investigation skills are built around biological hazards

Radiation Exposure

• Natural sources (radon gas) and man-made sources (medical imaging, nuclear industry)—radon is the second leading cause of lung cancer
• Ionizing radiation damages DNA directly—cancer risk increases with cumulative lifetime exposure
• ALARA principle (As Low As Reasonably Achievable)—the standard for radiation safety in occupational settings

Food Safety and Contamination

• Hazards include pathogens (Salmonella, E. coli), chemicals, and physical contaminants—causes millions of foodborne illness cases annually
• Temperature control, proper handling, and cooking are primary prevention methods—the "danger zone" is 40-140°F
• Regulatory frameworks (FDA, USDA) establish safety standards—HACCP (Hazard Analysis Critical Control Points) is the key food safety system

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Systemic and Occupational Hazards

These hazards demonstrate how environmental health intersects with social determinants—workplace conditions, housing quality, and community infrastructure all shape exposure patterns and health outcomes.

Climate Change

• Driven by greenhouse gas emissions—$CO_2$, methane, and nitrous oxide trap heat in the atmosphere
• Health impacts include heat-related illness, vector-borne disease expansion, and respiratory effects from wildfires—climate change is a "threat multiplier"
• Disproportionately affects vulnerable populations—elderly, outdoor workers, low-income communities, and those with pre-existing conditions

Occupational Hazards

• Include chemical exposures, physical risks, and ergonomic stressors—vary dramatically by industry and job type
• Can cause acute injuries, chronic diseases, and mental health problems—occupational lung diseases, musculoskeletal disorders, and workplace stress
• OSHA regulations and workplace safety training are primary prevention tools—employer responsibility is a key legal concept

Waste Management and Disposal

• Improper disposal contaminates air, water, and soil—landfills, incinerators, and illegal dumping each pose distinct risks
• Environmental justice concerns arise when waste facilities are sited in low-income communities—connects to health disparities
• Sustainable practices (reduce, reuse, recycle) minimize waste generation—hierarchy of waste management is a testable concept

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Quick Reference Table

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Self-Check Questions

1. Which two hazards share inhalation as the primary exposure route but differ in whether individual or policy-level interventions are most effective? Explain why the intervention level differs.

2. Identify three environmental health hazards that demonstrate bioaccumulation. For each, trace the pathway from environmental source to human exposure.

3. Compare and contrast how pesticides and endocrine disruptors cause harm. Why does the traditional "dose makes the poison" principle apply differently to each?

4. An FRQ asks you to discuss environmental health disparities. Which three hazards from this guide would best illustrate how social determinants shape exposure patterns? Justify your choices.

5. A community reports increased rates of both respiratory illness and neurological problems in children. Based on the hazards in this guide, what environmental factors would you investigate first, and what exposure pathways would you examine?