OVER the years cardiologists and public health experts have emphasised the adverse impact of traditional risk factors like smoking, hypertension, and diabetes on cardiovascular health.

In recent years we are beginning to recognise non-traditional risk factors that have only received scant attention. Environmental stressors like air pollution, smoke, noise pollution, and extreme temperatures have been shown to have many adverse effects on cardiovascular health.

As we tend to the current and emerging crisis from climate change, cardiologists are becoming more attentive to the impact of environmental stresses and pollution on the heart. While intuitively it is easy to predict that air pollution could lead to lung diseases and cancer, what is lost on many is that, of all the catastrophic consequences of air pollution, cardiovascular disease tops the list, ahead of cancer and lung diseases.

Air pollution and the global burden of disease

The Global Burden of Disease (GBD) project estimated that pollution accounted for about nine million deaths worldwide in 2019, with more than 50 per cent of those (an estimated five million deaths) resulting from cardiovascular disease.

Air pollution can be categorised into ambient fine particulate matter (aerodynamic-mass median diameter <2.5 μm compared to the average human hair which is about 70 µm in diameter) and household air pollution. Ambient air pollution results mainly from fossil fuel combustion and is a major problem globally, especially in highly industrialised nations and in major cities in low- and middle-income countries.

Household air pollution results primarily from indoor use of dirty solid fuels (for example, coal, wood, agricultural waste) and is a significant contributor to cardiovascular mortality in low-income countries and much less in highly industrialised nations.

Recognising the deleterious impact of air pollution on cardiovascular health, strict regulations in many countries have been introduced in the past few years. The United States is one country that has made significant effort through regulations to reduce the impact of air pollution on cardiovascular health. We have also seen some improvement in pollution control in western Europe, but for the developing world, we are witnessing an unprecedented rise in air pollution, noise pollution, and other environmental stressors that expectedly will drive the prevalence of cardiovascular diseases and could dull the impact of primary prevention measures focused on traditional risk factors for cardiovascular diseases.

According to the US Environmental Protection Agency (EPA), which tracks air quality trends across the country, air quality based on concentrations of the common pollutants has improved nationally since 1980. Lead emissions, for example, have dropped 76 per cent since 2000 and 99 per cent since 1980 as a result of the permanent phase out of leaded gasoline.

Unfortunately, despite the gains in mitigating air pollution in the USA from regulatory measures, the burning of fossil fuels continues to drive increasing levels of heat-trapping pollution, such as carbon dioxide in the Earth’s atmosphere.

The adverse impact of global warming is felt across multiple nations and has been linked to rising temperatures and extreme weather conditions resulting in devastating heat waves, frequent wildfires, rising air pollution, and other environmental stressors that trigger significant public health concerns, especially driving the surge of cardiovascular diseases.

Air pollution and heart health

There is a growing body of literature showing the adverse effects of air pollution on cardiovascular diseases, including hypertension, heart attack, cardiac arrest, stroke, cardiac arrest, arrhythmias, and recurrent or worsening heart failure. Air pollution, as shown by increased levels of particulate matter in the air, increases the relative risk of acute cardiovascular events by one per cent to three per cent within a few days. Prolonged exposure to air pollution increases this risk by about 10 per cent.

Air pollution has also been associated with an increased risk of arrhythmias. Long-term exposure to ambient air pollution has also been linked to sub-clinical cardiovascular disease and at higher levels result in doubling of cardiovascular risk.

A World Health Organisation (WHO) report in 2019 indicated that about 99 per cent of the world population was living in places where the WHO air quality guidelines of <10 mg/m3 for annual levels and <20 mg/m3 for daily levels were not met.

The American Heart Association, in a recent scientific statement, suggests that acute and chronic inhalation of particulate matter initiates extra pulmonary effects on the cardiovascular system via three broad “intermediary” pathways: the release of pro-inflammatory mediators or vasculoactive molecules; disturbance of the autonomic nervous system balance or heart rhythm by particle interactions with lung receptors; and potentially, the translocation of particulate matter or particle constituents directly into the systemic circulation.

According to a recent report from the World Heart Federation Air Pollution Expert Group, globally, air pollution ranked the fourth highest among risk factors for mortality, beating out high cholesterol, obesity, physical inactivity, and alcohol use, non-optimal temperature ranked 11th.

To secure the gains from primary prevention efforts against cardiovascular diseases, we must pay heed to the emerging science highlighting the impact of air pollution and environmental stress on public health in general and cardiovascular health in particular.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for the Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Send correspondence to info@caribbeanheart.com or call 876-906-2107