Every breath we take, every sip of water, every step we take in our environment has implications for our wellbeing that most of us rarely consider.
Environmental health represents the scientific discipline that studies how our surroundings—from the air we breathe to the water we drink—influence human health and disease 7 . This field recognizes that good health depends on clean air, a stable climate, preserved natural environments, and protection from harmful radiation and unsafe chemicals 1 .
That means nearly one in four deaths worldwide could be prevented through better environmental management.
From climate change intensifying disease patterns to pollution contaminating our resources, the environmental challenges we face are complex and interconnected—but so are the solutions. As we'll explore, understanding these connections empowers us to create healthier communities and a more sustainable future.
Environmental health is defined as "the field of science that studies how the environment influences human health and disease" 7 . It encompasses all aspects of our natural and built environments, including the air we breathe, the food we eat, the water we drink, and even the noise we hear 7 .
This field moves beyond identifying hazards to understanding the complex pathways through which our environment affects our wellbeing.
The scope of environmental studies is broad, covering everything from conservation and management of natural resources to controlling various forms of pollution and addressing population dynamics 7 .
What makes this field particularly challenging is that it requires an interdisciplinary approach, drawing from toxicology, epidemiology, ecology, and public policy to address these complex issues.
Living organisms or their products that increase disease risk, including bacteria, viruses, insects, and animals 7 .
Result from mismanagement of chemicals, including pesticides, lead, and environmental tobacco smoke 7 .
Factors in the environment that can harm the body directly, such as radiation from radon gas and ultraviolet light 7 .
Environmental factors that produce psychological changes expressed as stress, depression, and anxiety 7 .
The total amount of a hazard that comes in direct contact with your body, consisting of the source, environmental pathway, and contact point 7 .
The amount of a hazard that actually enters your body, which depends on duration of exposure, frequency of exposure, and body size 7 .
Some populations are more vulnerable to environmental hazards, including pregnant women, infants and children, the elderly, and those with pre-existing health conditions 7 .
The principle of environmental justice acknowledges that everyone has a right to live in an environment that doesn't make them sick, regardless of race, culture, or income 7 . Unfortunately, vulnerable populations often bear a disproportionate burden of environmental risks, with children particularly at risk due to their developing systems and unique exposure pathways .
Our planet faces unprecedented environmental challenges that pose significant threats to human health.
The climate crisis represents one of the most pressing environmental health threats of our time. 2024 was confirmed as the hottest year in history, with the global average temperature 1.60°C above pre-industrial levels 2 .
This unprecedented heating is causing catastrophic events worldwide—from devastating bushfires to intense heatwaves and flooding—that directly impact human health through injuries, displacement, and exposure to extreme temperatures 2 .
According to the World Health Organization, an estimated 4.2 to 7 million people die from air pollution worldwide every year, and nine out of ten people breathe air containing high levels of pollutants 2 .
In some regions like South Asia, air pollution cuts life expectancy by about five years 2 .
The plastic crisis continues to grow, with approximately 14 million tons of plastic entering oceans annually 2 .
Since 91% of all plastic ever produced has not been recycled, this represents a persistent environmental hazard that affects wildlife, ecosystems, and potentially human health through microplastic contamination 2 .
Hazardous chemicals from industrial processes, agriculture, and consumer products contaminate our air, water, and soil .
Particularly concerning are "forever chemicals" like PFAS that persist in the environment and accumulate in biological systems.
The ongoing decline of biodiversity has direct implications for human health. The population sizes of mammals, fish, birds, reptiles, and amphibians have declined by an average of 68% between 1970 and 2016 2 .
This biodiversity loss affects ecosystem services that support human health, including water purification, pollination of food crops, and regulation of infectious diseases.
Population sizes of mammals, fish, birds, reptiles, and amphibians 2
Children represent a particularly vulnerable population when it comes to environmental health threats. During pregnancy and early childhood, their developing bodies and systems are especially sensitive to environmental insults . Exposures during these "windows of vulnerability" can have long-term consequences, potentially leading to chronic diseases later in life. Disturbingly, patterns of disease among children are shifting worldwide from communicable to noncommunicable diseases, partly driven by environmental factors .
| Environmental Risk Factor | Estimated Annual Deaths | Key Health Impacts |
|---|---|---|
| Air Pollution | 4.2 - 7 million | Respiratory diseases, heart conditions, strokes |
| Climate Change | Increasing, not fully quantified | Heat stress, infectious disease spread, malnutrition |
| Water Pollution | Part of 13.7 million total | Diarrheal diseases, parasitic infections |
| Chemical Exposures | Part of 13.7 million total | Cancer, neurological disorders, reproductive issues |
In 1985, scientists made a disturbing discovery: a dramatic "hole" had formed in the ozone layer over Antarctica that opened up during the austral spring 3 . This protective layer in the stratosphere acts as Earth's natural sunscreen, shielding the planet from harmful ultraviolet (UV) radiation that can cause skin cancer, cataracts, and other adverse health effects 3 6 .
The cause was quickly identified: chlorofluorocarbons (CFCs)—chemicals then widely used in refrigeration, air conditioning, insulation, and aerosol propellants 3 . When CFCs drift into the stratosphere, they break down under certain seasonal conditions and destroy ozone molecules. Alarmingly, a single chlorine atom from CFCs can destroy more than 100,000 ozone molecules 6 .
The ozone layer protects life on Earth by absorbing harmful UVB radiation from the sun. Without this protection, increased UVB radiation would lead to:
While scientists had observed signs of ozone recovery in past years, a 2024 MIT-led study provided the first quantitative evidence with high statistical confidence that this recovery was directly due to reductions in ozone-depleting substances 3 .
The research team, led by Professor Susan Solomon and graduate student Peidong Wang, adapted a method called "fingerprinting" from climate science 3 . This innovative approach involved:
The study found that over time, the fingerprint they had identified in simulations became increasingly clear in actual observations. By 2018, the pattern was at its strongest, allowing the team to state with 95% confidence that ozone recovery was primarily due to reductions in ozone-depleting substances, rather than natural weather variability or increased greenhouse gas emissions 3 .
"There's been a lot of qualitative evidence showing that the Antarctic ozone hole is getting better. This is the first study that has quantified confidence in the recovery of the ozone hole. The conclusion is, with 95 percent confidence, it is recovering. Which is awesome. And it shows we can actually solve environmental problems."
Statistical confidence that ozone recovery is due to policy actions 3
The scientific discoveries about ozone depletion led to rapid international action. The Montreal Protocol, established in 1987, became a landmark international treaty that phased out the production and consumption of ozone-depleting substances 3 6 . To date, the protocol has led to the phase-out of over 99% of controlled ozone-depleting substances 9 .
The results have been dramatic: the ozone layer is now on track to recover to 1980s levels by the middle of this century, significantly reducing risks of skin cancer, cataracts, and ecosystem damage 9 . According to the World Meteorological Organization, the persistent later onset of the ozone hole has been identified as a robust indication of initial recovery 9 .
| Year | Key Event | Significance |
|---|---|---|
| 1975 | WMO issues first warning about ozone modification | First official scientific recognition of the problem |
| 1985 | Discovery of Antarctic ozone hole | Concrete evidence of significant ozone depletion |
| 1987 | Montreal Protocol established | International treaty to phase out ozone-depleting substances |
| 2016 | Solomon study shows signs of recovery | First qualitative evidence of ozone healing |
| 2024 | MIT study quantifies recovery | First quantitative evidence with 95% confidence |
| ~2035 | Projected occasional years without ozone hole | Expected milestone in recovery process |
| ~2066 | Full recovery over Antarctic projected | Expected complete recovery of ozone layer |
Understanding and addressing environmental health challenges requires sophisticated tools and approaches.
The standard unit for measuring ozone concentration, representing the number of molecules needed to create a layer 0.01 mm thick at 0°C and 1 atm of pressure 6 .
Networks of stations that collect data on temperature, humidity, wind, precipitation, and pollution 5 .
An analytical chemistry technique that measures the mass-to-charge ratio of ions with extreme precision 5 .
| Research Material | Function/Application | Example Use Case |
|---|---|---|
| Chemical tracers | Track movement of pollutants through environments | Studying how chemicals from biosolids enter food systems |
| Air sampling canisters | Collect ambient air for laboratory analysis | Measuring neighborhood variations in air pollution |
| Biological assays | Test toxicity of environmental samples | Determining health risks of chemical mixtures in waste |
| Satellite sensors | Remote monitoring of environmental conditions | Tracking global ozone levels and polar vortex dynamics |
| Climate models | Simulate atmospheric processes under different scenarios | Projecting future ozone recovery under various policy options |
The story of ozone layer recovery offers a powerful blueprint for addressing today's complex environmental health challenges. It demonstrates that when science, policy, and global cooperation align, we can solve seemingly intractable problems. As United Nations Secretary-General António Guterres noted, "This achievement reminds us that when nations heed the warnings of science, progress is possible" 9 .
Support environmental health research and data collection
Implement policies based on scientific evidence
Recognize that environmental health is an investment in our collective future
Yet many challenges remain. From the climate crisis to pervasive pollution and biodiversity loss, the environmental determinants of health continue to evolve. The recent defunding of critical environmental health research projects threatens our ability to understand and address these issues 5 .
As Benjamin Zaitchik from Johns Hopkins University lamented after his grant was canceled, without data, "cities and states have budgets and can't fix everything. They have to prioritize, and that can't happen in the dark" 5 .
By applying the lessons from past successes like the Montreal Protocol to current challenges, we can create a world where everyone can breathe clean air, drink safe water, and live in healthy environments.
Our health—and the health of generations to come—depends on the choices we make today.