Environmental Health Guide

Introduction

The air we breathe, the water we drink, the food we eat, and the chemicals we encounter in our homes and workplaces all shape our health. The World Health Organization estimates that 13 million deaths per year — 24 percent of all global deaths — are attributable to modifiable environmental risk factors. These deaths are preventable. Environmental health, the branch of public health concerned with the physical, chemical, and biological factors in the environment that affect human well-being, seeks to identify these risks and eliminate them.

Environmental health issues are not distributed equally. Low-income countries bear the heaviest burden of environmental disease, accounting for 85 percent of environmentally attributable deaths. Within countries, marginalized communities — especially low-income populations and people of color — face higher exposure to air pollution, contaminated water, toxic chemicals, and hazardous waste. This guide examines the major environmental health challenges of our time, including air and water pollution, chemical toxins, climate-related health threats, and the policy frameworks designed to protect populations.

Air Pollution

Air pollution is the single greatest environmental health risk. The WHO reports that 99 percent of the world’s population breathes air that exceeds its air quality guideline limits, causing an estimated 7 million premature deaths annually.

Outdoor Air Pollution

Outdoor air pollution is caused primarily by the combustion of fossil fuels for transportation, power generation, and industry. Fine particulate matter — particles smaller than 2.5 micrometers in diameter — is the most dangerous component. PM2.5 penetrates deep into the lungs, crosses into the bloodstream, and causes cardiovascular disease, respiratory illness, lung cancer, and stroke. Ground-level ozone, nitrogen dioxide, and sulfur dioxide are also significant pollutants.

The health impacts are staggering. A 2022 study in The Lancet Planetary Health found that long-term exposure to PM2.5 was associated with a 9 percent increase in all-cause mortality for every 10 micrograms per cubic meter increase in concentration. Globally, exposure to air pollution reduces average life expectancy by nearly two years, according to the Air Quality Life Index. The most polluted cities are in South Asia: Delhi, Dhaka, and Lahore regularly record PM2.5 concentrations more than 10 times the WHO guideline of 5 micrograms per cubic meter.

Indoor Air Pollution

Indoor air pollution is a crisis in low- and middle-income countries. Approximately 2.6 billion people depend on solid fuels — wood, charcoal, coal, and dung — for cooking and heating. Burning these fuels in open fires or traditional stoves produces high levels of PM2.5, carbon monoxide, and other toxins. The WHO estimates that household air pollution causes 3.2 million premature deaths annually, primarily from pneumonia, stroke, heart disease, and lung cancer. Women and children are disproportionately affected because they spend more time near the cooking fire.

Solutions include clean cooking stoves, biogas digesters, solar cookers, and, most importantly, access to clean fuels such as liquefied petroleum gas and electricity. Programs like the Clean Cooking Alliance have distributed millions of improved stoves, but adoption rates remain uneven.

Water Quality and Sanitation

Access to safe drinking water and adequate sanitation is a human right, yet 2.2 billion people — one in four — lack safely managed drinking water. Contaminated water causes diarrheal diseases, cholera, typhoid, and hepatitis A, killing an estimated 1.4 million people each year, mostly children under five. The leading cause of water contamination is untreated sewage. Globally, 44 percent of household wastewater is discharged without treatment, according to the United Nations. Agricultural runoff — containing fertilizers, pesticides, and animal waste — is the leading cause of surface water pollution in many regions. Industrial effluents introduce heavy metals and toxic chemicals into waterways.

In high-income countries, water quality issues are more subtle but still significant. The Flint water crisis in Michigan, where lead from corroded pipes contaminated drinking water between 2014 and 2019, exposed the inadequacy of water infrastructure and regulatory oversight in the United States. Lead exposure in children causes irreversible cognitive impairment, reduced IQ, and behavioral problems. The American Academy of Pediatrics states that there is no safe level of lead in a child’s blood.

Toxic Chemicals and Hazardous Waste

Modern industrial society produces thousands of synthetic chemicals, many of which have known or suspected health effects. Persistent organic pollutants — including polychlorinated biphenyls (PCBs), dioxins, and certain pesticides — accumulate in the food chain and remain in the environment for decades. Endocrine-disrupting chemicals such as bisphenol A and phthalates interfere with hormone systems and are linked to reproductive disorders, developmental abnormalities, and certain cancers.

Workplace exposure to hazardous chemicals causes an estimated 745,000 deaths annually, according to the International Labour Organization. Asbestos alone kills more than 200,000 people each year from mesothelioma, lung cancer, and asbestosis. The Stockholm Convention on Persistent Organic Pollutants, ratified by 185 countries, has banned or restricted the production of many of the most dangerous chemicals. The Global Alliance to Eliminate Lead Paint has helped phase out lead in paint in 112 countries. But the production and use of toxic chemicals continues to grow globally, especially in developing countries where regulations are weaker.

Pesticides

Agricultural pesticides are designed to kill living organisms, and they do not discriminate between target pests and non-target species, including humans. The WHO estimates that 200,000 people die each year from acute pesticide poisoning, the majority of them farmers in low-income countries who lack protective equipment and training. Chronic exposure has been linked to Parkinson’s disease, various cancers, and reproductive harm. The European Union has banned more than 200 pesticides that are still approved for use in the United States, India, and Brazil. Glyphosate, the most widely used herbicide globally, has been classified as probably carcinogenic to humans by the WHO’s International Agency for Research on Cancer.

Children are especially vulnerable to pesticide exposure because their bodies are still developing and they absorb more toxins relative to their body weight. The American Academy of Pediatrics recommends choosing organic produce when possible for fruits and vegetables with the highest pesticide residues — strawberries, spinach, kale, nectarines, apples, and grapes. Community-based programs such as integrated pest management reduce reliance on chemical pesticides by using biological controls, crop rotation, and habitat management to control pests without toxic chemicals.

Climate Change as a Health Emergency

Climate change is transforming the landscape of global health. The IPCC’s Sixth Assessment Report concluded that climate change poses serious risks to human health, with impacts already observed across every region. Heat waves are killing more people as temperatures rise. The 2022 European heat wave caused an estimated 62,000 excess deaths. Warmer temperatures expand the range of disease-carrying insects. Dengue, malaria, Zika, and Lyme disease are appearing in regions where they were previously unknown. Changing rainfall patterns affect water quality and food production, increasing the risk of malnutrition and waterborne disease.

The health care sector itself is a contributor. If global health care were a country, it would be the fifth largest greenhouse gas emitter on the planet. Hospitals, pharmaceuticals, and supply chains produce 4.4 percent of global emissions. Efforts to decarbonize health care are underway, with more than 100 countries committing to net-zero health systems under the WHO’s Alliance for Transformative Action on Climate and Health.

Environmental Health Policy

Protecting human health from environmental hazards requires regulation, monitoring, and enforcement. The Clean Air Act in the United States, since its amendment in 1970, has reduced the concentration of six common pollutants by an average of 78 percent while the economy tripled. The European Union’s REACH regulation requires companies to register and assess the safety of chemicals before they enter the market. The Minamata Convention on Mercury, in force since 2017, aims to reduce mercury emissions from artisanal gold mining and coal combustion.

Environmental health also depends on environmental justice. Communities that face the worst environmental conditions often have the least political power to demand change. Policies that prioritize equitable enforcement, community engagement, and cumulative risk assessment are essential for protecting the most vulnerable populations. The intersection of environmental health and social equity demands that pollution controls and clean energy transitions be designed with affected communities at the table, not as an afterthought.

FAQ

What is the leading environmental cause of death? Air pollution is the leading environmental cause of death worldwide, responsible for approximately 7 million premature deaths annually from stroke, heart disease, lung cancer, and respiratory infections.

Is tap water safe to drink? In the United States, Canada, and most of Europe, tap water is generally safe because of treatment and monitoring. However, lead pipes in older infrastructure and agricultural runoff can cause contamination. Boiling water does not remove lead or chemical contaminants.

How does climate change affect human health? Climate change increases the frequency of heat waves, spreads infectious diseases, degrades air quality, reduces food and water security, and causes mental health stress from extreme weather events.

What is environmental justice? Environmental justice is the principle that all people, regardless of race, income, or national origin, have the right to equal protection from environmental hazards and equal access to environmental benefits such as clean air, water, and green space.

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