Fine particles in air pollution — A global health menace
How air pollution damages the body through oxidative stress and chronic inflammation
Air pollution has become one of the world’s major public-health challenges. The health threat is so significant that the World Health Organisation (WHO) continues to devote considerable attention to its prevention and control.
Unfortunately, many people remain unaware of the wide-ranging health consequences of breathing polluted air, particularly air containing fine particulate matter.
On my Cocoa Nutrition & Health channel, I have discussed the health implications of fine particles in air pollution, including their association with metabolic disorders. After one such discussion, a viewer asked whether I was really sure that long-term exposure to fine particles could increase the risk of overweight and obesity. The question demonstrated how little-known the effects of air pollution beyond the lungs still are.
World Health Organisation (WHO)
According to the WHO, about 99 per cent of the world’s population is exposed to levels of fine-particle pollution above the WHO annual air-quality guideline for PM2.5 of 5 micrograms per cubic metre (5 µg/m³).
Air pollution was ranked the second leading risk factor for mortality in 2021, ahead of tobacco smoke and dietary risks. Particulate-matter-attributable air pollution, as reported under Sustainable Development Goal Indicator 3.9.1, accounted for approximately 6.6 million deaths in 2021 (WHO technical brief/paper on air pollution).
These deaths include those associated with ischaemic heart disease, stroke, chronic obstructive pulmonary disease (COPD), acute lower respiratory infections, type 2 diabetes and lung cancer. Overall, non-communicable diseases account for nearly 84 per cent of total deaths attributable to air pollution.
These figures demonstrate why air pollution should be regarded not simply as an environmental problem, but as a major global health emergency.
Reactive oxygen species and human health
To understand how fine particles can damage the body, we need to understand reactive oxygen species (ROS).
Oxygen is essential for life. As our cells use oxygen to generate energy, they naturally produce reactive oxygen species. These include free radicals such as superoxide anion and hydroxyl radicals, as well as non-radical molecules such as hydrogen peroxide.
ROS are therefore not always harmful. At low and carefully controlled levels, they perform important functions in cellular signalling, metabolism and immune defence.
Healthy cells maintain a delicate balance between the production of ROS and the body’s antioxidant defence systems. These defences include enzymes such as superoxide dismutase and catalase, together with non-enzymatic antioxidant compounds.
Problems arise when excessive ROS production overwhelms these natural defences. The resulting imbalance is known as oxidative stress.
ROS can arise naturally within the body, particularly during cellular energy production, while external factors such as environmental pollutants, ultraviolet radiation and tobacco smoke can increase oxidative stress (Rahman et al. (2026), Oxidative stress in chronic disease: Mechanisms, therapeutic strategies, and future direction, Advances in Redox Research 20 (2026) 100177).
The body itself generates ROS through normal physiological processes. Mitochondria — the structures within cells responsible for producing much of our energy — are an important endogenous source.
However, ROS can also be generated or increased by external environmental and lifestyle factors, including air pollution, tobacco smoke and radiation.
Fine particles in air pollution are important environmental stressors because exposure can promote excessive ROS production, potentially overwhelming antioxidant defences and shifting the body’s normal redox balance towards oxidative stress.
From oxidative stress to chronic disease
When oxidative stress persists, free radicals and other reactive molecules can damage important components of our cells.
Cell membranes may undergo lipid peroxidation; proteins may become damaged; cellular signalling may be disrupted; and DNA may sustain oxidative injury.
Persistent oxidative stress can also activate inflammatory pathways. Instead of inflammation being a temporary protective response to injury or infection, it may become chronic low-grade inflammation.
This combination of oxidative stress, inflammation and disturbed cellular signalling can contribute to the development and progression of several chronic diseases.
In cardiovascular disease, oxidative modification of low-density lipoprotein (LDL) can contribute to plaque formation, atherosclerosis and blood-vessel dysfunction.
In type 2 diabetes, redox imbalance can interfere with insulin signalling and promote metabolic dysfunction.
Sustained oxidative damage to DNA may contribute to mutations and other cellular changes involved in cancer development.
Oxidative damage to neurons has also been implicated in processes associated with neurodegenerative diseases such as Alzheimer’s disease.
Air pollution does not affect only the lungs
One of the greatest misconceptions about air pollution is that its effects are confined to the respiratory system. They are not.
Fine particles are so small that they can bypass some of the body’s natural filtering mechanisms in the nose and upper airways and penetrate deep into the lungs. Some particle components can subsequently reach the bloodstream, contributing to effects in organs and systems throughout the body.
Air-pollution particles have even been detected in cells in the human placenta. Exposure to air pollution during pregnancy has been associated with adverse outcomes, including low birth weight, preterm delivery and neurological effects.
The message is therefore clear: what we breathe can affect virtually every part of the body.
Organs and systems affected by air pollution. Source: Adapted from Thurston et al. Disease outcomes highlighted reflect ATS/ERS assessments of established adverse effects of air pollution, together with diseases included in WHO assessments and conditions for which evidence is emerging.
As the figure demonstrates, air pollution has been associated with effects involving the lungs, brain, heart and cardiovascular system, liver, kidneys, pancreas, blood vessels and reproductive systems.
Africa bears a disproportionate burden
The health burden of air pollution is not evenly distributed across the world.
Low- and middle-income countries experience an annual rate of approximately 111 deaths per 100,000 people attributable to PM2.5, compared with approximately 19 deaths per 100,000 in high-income countries.
The WHO African Region bears a particularly heavy burden.
Figure 3. Global PM2.5-attributed age-standardised mortality rates per 100,000 population by WHO region, 2021.
The WHO data presented in Figure 3 show approximately 154 deaths per 100,000 in Africa, compared with 129 in South-East Asia, 121 in the Eastern Mediterranean, 80 in the Western Pacific, 36 in Europe and 34 in the Americas.
This disproportionate burden makes air pollution particularly relevant to Africa and underscores the need for strong public-health and environmental interventions.
What can we do?
Reducing exposure must remain the first line of defence.
Individuals can, where practicable, avoid areas with very high pollution, wear appropriate protective masks when necessary, improve indoor ventilation and avoid tobacco smoking and second-hand smoke. However, individuals alone cannot solve the problem.
Air pollution requires policy interventions at the highest levels, including measures aimed at reducing pollution at its source, improving air-quality monitoring, controlling harmful emissions and increasing public awareness.
Where does polyphenol-rich cocoa fit?
Against the background of oxidative stress and chronic inflammation, there is growing scientific interest in diets containing naturally occurring antioxidant and anti-inflammatory compounds.
Polyphenol-rich cocoa contains bioactive compounds that have been studied for their antioxidant, anti-inflammatory and vascular effects. As part of a balanced diet and healthy lifestyle, polyphenol-rich foods such as cocoa can therefore help support the body’s natural defence systems against oxidative and inflammatory stress.
The most important intervention remains preventing and reducing exposure to polluted air.
The science sends a powerful message: clean air is not a luxury. It is fundamental to human health.
Protecting the quality of the air we breathe must therefore become a responsibility shared by all.
BY DR. EDWARD O. AMPORFUL
The writer is the Clinical Pharmacist and former Chief Pharmacist, Cocoa Clinic.
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