How does air pollution affect health?

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Air pollution is a growing problem around the world as various industries produce increasing amounts of carbon dioxide, methane, and other pollutants. These pollutants have detrimental effects on climate change, air quality, and ecosystems. Air pollution can be damaging to human health as, among other things, it can trigger the development of respiratory problems. But can air pollution have other detrimental effects? And if so, how does air pollution affect health?

Brain Health

In addition to the known consequences, researchers are interested in determining whether air pollution is associated with neurological disorders, such as Alzheimer’s disease, dementia, Parkinson’s disease, and multiple sclerosis. Neurological disorders are some of the most prevalent disabilities and many do not have a cure A Canadian study published in the journal Environmental Health examined the relationship between air pollution and brain health. 

Researchers examined a population of 678,000 adults between the ages of 45 and 84 living in Canada between January 1994 and December 1998. They looked at their proximity to major roads and highways, which are a significant source of air pollution. They then followed up with the group between January 1999 and December 2003 to see whether they were diagnosed with dementia, Alzheimer’s disease, Parkinson’s disease, or multiple sclerosis.

The researchers found that living within 50 metres of a major road was linked to an increased risk of dementia, Parkinson’s disease, Alzheimer’s, and multiple sclerosis. Additionally, living within 150 metres of a highway was associated with an increased risk of all these conditions. The association is believed to be caused by an increased level of air pollution.

The researchers also found that the presence of green space appeared to be protective against these negative effects. According to the lead author of the study Weiran Yuchi, “green spaces appear to have some protective effects in reducing the risk of developing one or more of these disorders. More research is needed, but our findings do suggest that urban planning efforts to increase accessibility to green spaces and to reduce motor vehicle traffic would be beneficial for neurological health.”

The results of this study suggest that there could potentially be an association between proximity to major roadways and neurological disorders. More research is needed to determine the strength of this relationship, and what preventive measures might successfully mitigate this risk.

Cardiovascular Disease

Air pollution is widely known to have a negative effect on the cardiovascular system. Air pollution and cardiovascular disease are intrinsically linked but the extent of the impact on hospital admissions has not previously been investigated.

Published in the British Medical Journal, a large research study looked at hospital admissions due to cardiovascular disease caused by fine particulate air pollution. The study reported that short-term exposure to fine particulate matter air pollution was associated with increased hospital admissions for all types of cardiovascular disease except haemorrhagic stroke, even where exposure levels did not exceed current regulatory limits.

Stroke

Several studies have suggested a link between long-term exposure to air pollution and stroke.

A study published in BMJ investigated the association between long-term exposure to ambient air pollution and stroke. Using spatiotemporal statistical models based on satellite remote sensing data, researchers obtained monthly estimates of air pollution levels around the participants’ residences between the years 2000 and 2015.

The results of the study report an almost linear exposure and response relationship between long-term exposure to air pollution and stroke.  The findings suggest that long term exposure to high concentrations of ambient air pollution is associated with an increased risk of stroke.

Glaucoma

Glaucoma is a common eye disease that causes injury to the optic nerve and leads to permanent vision loss or eye blindness. Increased intraocular pressure has been known to be a risk factor for glaucoma.

In a study published in Investigative Ophthalmology & Visual Science, researchers studied the link between air pollution and glaucoma. Participants who lived in regions with increased air pollution were more prone to developing glaucoma.

Additionally, those with glaucoma have a thinner retina and the researchers found that a thinner retina was linked with increased exposure to air pollution, however, the study did not find a link between air pollution and increased eye pressure. The researchers further stated that increased eye pressure does not play a role in the relationship between air pollution and glaucoma – they suggested that it could be due to a different mechanism.

This study reports that increased air pollution is linked to glaucoma but this relationship has not proven to be causal. According to Professor Paul Foster, “While we cannot confirm yet that the association is causal, we hope to continue our research to determine whether air pollution does indeed cause glaucoma, and to find out if there are any avoidance strategies that could help people reduce their exposure to air pollution to mitigate the health risks.” Further research is required.

Birth outcomes

Adverse birth outcomes can lead to disease and mortality. There have been some studies that have seen links of adverse birth outcomes to air pollution, while others have not.

A cohort study published by Environmental Research included data on pregnant women and their live births. Researchers found that out of all the births, 7,5% were preterm births and just 5.7% had low birth weights. They found that the presence of sulphur dioxide in the air was the main cause of these results.

Children’s health

In a study published in the journal Environmental Research, researchers at the Columbia Center for Children’s Environmental Health in the United States reviewed 205 peer-reviewed studies published between 2000-2018 to determine the connection between fossil fuel combustion pollutants and the various health effects in children.

The health effects of air pollution on children includes adverse birth outcomes, damaged cognitive and behavioral development, respiratory illness, and the possibility of developing childhood cancer.

The authors found that exposure to fine particles during pregnancy resulted in a thinner cortex in several regions of the brain of children between the ages of 6-10. The abnormalities found were linked to ADHD, low birth weight, adverse cognitive and behavioral outcomes, MRI brain changes, autism, and asthma.  A slower development and social competence were also associated with air pollution exposure during pregnancy.

Breast cancer

Research suggests that there may be an association between air pollution and breast cancer. To investigate this possible association further, researchers in Canada published a study in Environmental Epidemiology on whether exposure to fine particulate matter (PM2.5) was associated with breast cancer incidence.

The study found that there was a positive association between breast cancer in premenopausal women and fine particulate matter in the area of residence at the time the participants enrolled in the study. This association grew with increases in fine particulate matter exposure by a factor of 26% for every 10ug/m3 increase in PM2.5.

References:

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Jiang, X.-Q., Mei, X.-D., & Feng, D. (2016). Air pollution and chronic airway diseases: what should people know and do? Journal of Thoracic Disease8(1), 31–40. doi: 10.3978/j.issn.2072-1439.2015.11.50

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Photo by Pixabay from Pexels: https://www.pexels.com/photo/air-air-pollution-climate-change-dawn-221012/

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