The Air You Breath Is Driving Your Risk Of Heart Disease

Why air pollution is one of the biggest unrecognised risk factors for heart disease.

I think about cardiovascular risk pretty much all day, and I have to say I was surprised to learn that air pollution was the 4th leading cause of death worldwide.

Air pollution is thought to be responsible for 9 million deaths in 2019, and 62% of those were related to cardiovascular disease¹.

So if preventing cardiovascular disease is a priority, the role of air pollution is something you need to know about.

What Is Air Pollution

Air pollution is a complex mix of ingredients, but the factor that is most understood is fine particulate matter less than 2.5μm in diameter (PM2.5).

The primary source of PM2.5 varies by country; in more developed counties, it results from coal burning, industrial plants, transport vehicles and even incense and aerosol sprays.

In lower-income countries, the greatest exposure is driven mostly by burning biomass fuels, including wood, coal, straw and dung.

Air pollution is a very dynamic property, even on an hour-to-hour or day-to-day basis, but in general, certain regions have much higher levels than others.

The 2005 WHO Air Quality Guidelines suggested an annual exposure of no more than 10 PM2.5 μg/m3. As of 2021, this has been reduced to 5 PM2.5 μg/m3². The US National Quality Air Quality Ambient Standard, however, has set an annual mean exposure limit of 12 μg/m3.

It is estimated that 91% of the world's population lives in an area where the annual air pollution levels exceed 10 PM2.5 μg/m3³.

Air Pollution & Cardiovascular Disease

The relationship between air pollution and cardiovascular disease is clear.

The greater the exposure, the higher the risk.

For every 10 PM2.5 μg/m3 mean annual increase in exposure, the risk of dying from heart disease increases between 16 to 31%⁴.

The risk appears to rise rapidly with even moderate levels of exposure and then plateau at very high levels.

The greatest risk appears to be that of stroke over coronary artery disease.

Even short-term high levels of exposure to fine particulate matter increase the risk of dying from heart disease in the days following the exposure, emphasising that we all need to be mindful of this, particularly those at the highest risk⁵.

This near-term dynamic risk also applies to arrhythmia, including atrial fibrillation and acute asthma episodes⁶.

What About Confounders?

All of the large-scale research in this area is observational rather than randomised data which means that there is a significant potential for confounding variables to play a major role.

If a person is exposed to high levels of fine particulate matter, they are also very likely to live in a disadvantaged area, smoke or have other independent risk factors for cardiovascular disease.

But we will never have large randomised trials in this area, so we have to make do with observational data and all its limitations.

Would you sign up to be potentially randomised into the ‘exposed to daily high levels of air pollution arm’?! I thought not.

In order to limit the impact of confounding variables, a recent study attempted to exclude them as best as possible by following individuals for ten years in Northern California, where access to medical records and other potential confounders was available.

For individuals who exceed the annual US standard of 12 PM2.5 μg/m3 and even 10 PM2.5 μg/m3, there was up to a 50% increased risk of dying from heart disease.

When adjusted for variables including age, socio-economic status, BMI, smoking status and other cardiovascular risks, there was still a 21% increased risk of dying from heart disease⁷.

Even though confounders do play a major role in the observational data, it is likely that significant risk still remains.

Geography Is Key

Air pollution is a global issue, and exposure, even at levels below current ‘safe’ thresholds, still accounts for increased risk.

But for developing nations, that risk is off the charts in comparison.

It is very clear that all air pollution risk is not evenly distributed.

On a global basis, annual exposure levels are over four times the current recommended safe levels, and these safe recommendation levels continue to fall.

Reducing Air Pollution

The easy answer here is to move developing nations into developed nation status. Often the suggestion here is to massively reduce fossil fuel consumption (A major contributor) and move to a more carbon-neutral energy consumption pattern.

If only it were so easy.

How do you think most nations went from developing to developed in the past?

Answer: By maximising the benefit of carbon-rich fuels.

I am not a climate or energy expert, but I know that transitioning developing nations to less carbon-emitting technologies is a very complex process and will likely be done in stages.

Just like pretty much how every other developed nation made that transition. Just hopefully, faster.

The answer here is unlikely to reside with individuals either, but that does not mean we cannot be aware of the risks and modify our actions if it might be reasonable.

But change is possible.

Take Paris, for example. Over the last 20 years, the city has made considerable efforts to reduce car traffic in the city centre.

The impact on air quality has been significant.

What also has to be taken into consideration is the technology cars use to emit less pollution so all the reductions shown here cannot be attributed to simply fewer cars.

But it shows that with a multidimensional approach, change is possible.

Live Air Quality Data

Air quality is always changing. If you want to minimise your annual exposure, the only reliable way to do this is by spending most of your time outside of a major urban centre.

While I am sure many of us would love to spend our days in the countryside, it will not be possible for many.

But you can choose when to limit your exposure when conditions are very poor.

For those with home air conditioning systems, it is important to consider installing or updating appropriate air filtration systems.

Live air quality data is available for most regions.

Below are some examples from New York (Current wildfires subsiding in Canada), Sydney, London and Dublin for comparison.

This data was acquired from https://www.iqair.com/air-quality-map.

New York, NY, USA

Sydney, NSW, Australia.

London, UK.

Dublin, Ireland.

Living in the world comes with risks.

We all need to be aware of the risks that impact us and what we might be able to do to avoid them when possible.

When it comes to air pollution, we can take near-term measures to avoid peak levels of pollution and hopefully see a future where global levels have reduced in an equitable manner.

If you take nothing else from this article, maybe you can take it as motivation to spend some time in the wilderness.

There might be a risk of wild animals and falls….

But at least the air quality will be good!

Unless, of course, you encounter a wildfire….

1. Rajagopalan S, Landrigan PJ. Pollution and the Heart. N Engl J Med. 2021 Nov 11;385(20):1881-1892. doi: 10.1056/NEJMra2030281. PMID: 34758254.

2. https://www.who.int/news-room/feature-stories/detail/what-are-the-who-air-quality-guidelines

3. Rajagopalan S, Landrigan PJ. Pollution and the Heart. N Engl J Med. 2021 Nov 11;385(20):1881-1892. doi: 10.1056/NEJMra2030281. PMID: 34758254.

4. Liang F, Liu F, Huang K, et al. Long- term exposure to fine particulate matter and cardiovascular disease in China. J Am Coll Cardiol 2020;75:707-17.

5. Short-Term Exposure to Ambient Air Pollution and Mortality From Myocardial Infarction. J Am Coll Cardiol. 2021 Jan 26;77(3):271-281. doi: 10.1016/j.jacc.2020.11.033. PMID: 33478650.

6. Hourly air pollution exposure and the onset of symptomatic arrhythmia: an individual-level case–crossover study in 322 Chinese cities. CMAJ. 2023;195:E601-E611.

7. Alexeeff SE, Deosaransingh K, Van Den Eeden S, Schwartz J, Liao NS, Sidney S. Association of Long-term Exposure to Particulate Air Pollution With Cardiovascular Events in California. JAMA Netw Open. 2023 Feb 1;6(2):e230561.