“Air pollution does not recognize borders.”  I like this quotation. It speaks to the need for international cooperation, international data gathering, and international action. However, we do see places where air pollution (amounts of PMs measured annually) and the associated mortality and morbidity are worse. This article is here to highlight these areas.
INCOME – when looking specifically at the deaths caused by air pollution, apparently, more than 90% of them occur in low- and middle-income countries.  This should not be surprising – as discussed, there is a higher proportion of the population who are both more likely to have open flames in the home, and less likely to have access to clean energy technologies. We also see that where improved access to clean fuels is happening, it is not keeping pace with population growth.  This is a problem of access to technology on a large scale.
Household air pollution in these circumstances: 
- almost doubles the risk for childhood pneumonia, is responsible for 45% of all pneumonia deaths under five years old, and 28% of all pneumonia deaths in adults;
- is attributed 25% of premature adult deaths from COPD, and increases the risk of COPD compared to those using clean energy twofold in women, and twofold in men who smoke;
- it is attributed 12% of premature deaths due to stroke, 11% of premature deaths due to ischaemic heart disease, and 17% of premature deaths due to lung cancer;
- may be linked to low birth weight, tuberculosis, cataracts, nasopharyngeal and laryngeal cancers
Yes, other factors increase risk, and we see that they are those which are also massively affected by socioeconomic group: hypertension, diet, lack of physical activity, smoking, suboptimal breastfeeding, malnourishment, second-hand smoke. But the effect of air pollution should not be ignored, and in these situations, it is so possible to affect it.
And the unsafe fuels have other risks too: kerosene ingestion is a leading cause of childhood poisonings, and in general we see burns and other injuries.
“Air pollution threatens us all, but the poorest and most marginalized people bear the brunt of the burden” – Dr Tedros Adhanom Ghebreyesus, Director-General of WHO .
GEOGRAPHY – for the most part this pretty much follows income and population density / industry activity, meaning yes where you are matters as much as who you are. As we might expect, low-income countries tend to be worse off in terms of health outcomes, and some megacities exceed the WHO’s guidelines for air quality by more than 5 times. There’s also been a lot of work on shipping routes . We can assume that areas which see forest fires and the like experience spikes in their PM levels seasonally.
It’s worth noting that the WHO doesn’t have data on all the world’s cities, with particular paucity in Africa and the Western Pacific. In Africa, the database still only has information on 8 of 47 countries.  However, with the data they do have, those low- and middle-income countries worst affected are found in Asia and Africa, followed by the Eastern Mediterranean region, Europe and the Americas. 
CHILDREN – We have already discussed the startling rate of death from pneumonia attributable to household air pollution in low income countries where there are poor quality fires in the home. However, we see particularly adverse effects on children no matter the context, because physiologically children are very vulnerable to air pollution . We think children receive higher “doses” of particles in the air they breathe. Why? Because we know that the concentration of pollutants in the air is generally higher in air which is closer to ground level. It is also logical that the particles could have a greater long-term negative impact on children, because their bodies are developing, and damage caused now can only persist and build throughout their lives. A WHO study  found that:
- 600,000 children under the age of fifteen die annually from the combined effects of ambient and household air pollution (again, I don’t know exactly how they arrived at that figure, but if there’s a source I would trust when it’s late on a Sunday morning and my statistics brain is groaning to a halt, it’s the WHO)
- Ambient and household air pollution apparently cause more than 50% of acute lower respiratory tract infections in children under five years of age in low- and middle-income countries
- In poorer countries, 98% of children under five years old are exposed to PM2.5 levels above WHO guidelines
- In high-income countries, 52% of children under five years old are exposed to PM2.5 levels above WHO air quality guidelines.
- They linked air pollution to:
- Neurodevelopment (via lower cognitive test outcomes; look up the specifics of that as you will)
- Lung function, especially asthma
- Childhood cancer
In order to keep things standardized throughout this article I think we should change this open removing what I have in brackets to PREGNANCY – (This concern about getting a healthy start also applies to pregnant women:) a WHO report concludes that “when pregnant women are exposed to polluted air, they are more likely to give birth prematurely, and have small, low birth-weight children. Air pollution also impacts neurodevelopment and cognitive ability and can trigger asthma, and childhood cancer. Children who have been exposed to high levels of air pollution may be at greater risk for chronic diseases such as cardiovascular disease later in life.” Whew. 
It’s worth pointing out that fine particulates in the atmosphere are not the only thing which we suspect is contributing to cases of respiratory disease. For example, take asthma. Another contributor to increasing rates of asthma is pollen levels, which are increasing with temperatures and levels of carbon dioxide. Indoor mould (also strongly associated with socioeconomic context) and the good old second-hand cigarette smoke all make asthma worse. However, it cannot be denied that these PMs are a huge factor, and one to which we are able to make significant improvement.
Next we look at what we can do, not individually but as a global community. It’ll be tough but our next article looks at exactly how we can tackle these issues.
Author Details: Dr. Katherine Smith, Foundation Year 2
Editor’s Note: Apologies for the delay in publishing this article, unfortunately the team has been tied up with nights, on-calls, applications for further clinical work, and other projects. We’re aiming to increase the frequency as we can in the coming months but realistically we may have to reduce the cadence of these articles to once every 3 weeks or one per month for a short while. If you want to help speed this up, please get in contact with us to submit your own articles!
- World Health Organisation, “9 out of 10 people worldwide breathe polluted air, but more countries are taking action,” 2 May 2018. [Online]. Available: https://www.who.int/news-room/detail/02-05-2018-9-out-of-10-people-worldwide-breathe-polluted-air-but-more-countries-are-taking-action. [Accessed 4 November 2018].
- World Health Organisation, “Household air pollution and health,” 8 May 2018. [Online]. Available: Exposure to household air pollution almost doubles the risk for childhood pneumonia and is responsible for 45% of all pneumonia deaths in children less than 5 years old. . [Accessed 15 December 2018].
- M. Sofiev, J. J. Winebrake, L. Johansson, E. W. Carr, M. Prank, J. Soares, J. Vira, R. Kouznetsov, J.-P. Jalkanen and J. J. Corbett, “Cleaner fuels for ships provide public health benefits with climate tradeoffs,” Nature
- World Health Organisation, “More than 90% of the world’s children breathe toxic air every day,” 29 October 2018. [Online]. Available: http://www.who.int/news-room/detail/29-10-2018-more-than-90-of-the-world%E2%80%99s-children-breathe-toxic-air-every-day. [Accessed 4 November 2018].