Exposure to air pollution not only increases risk of asthma attacks but also of disease onset in children
The researchers found that while children whose parents had asthma were still more likely to develop the chronic disease, those who were exposed to higher levels of small particulate matter (PM 2.5) and nitrate pollution also had an increased risk of asthma onset.
Asthma is one of the most prevalent diseases among children globally, and this prevalence has been on the rise over the last few decades. Most research indicates that genetic susceptibility (if either of the parents has asthma) is a major risk factor for children developing asthma at an early age. But a recent study published in the British Medical Journal (BMJ) indicates that air pollution can also lead to the onset of childhood asthma.
Link between air pollution and asthma
The link between air pollution and asthma is well-known and appears quite logical. As a 2017 study in PLOS One shows, outdoor air pollutants like ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), and particulate matter (PM) can induce asthma symptoms or aggravate such symptoms to the extent of requiring hospitalisation.
Another study in Current Opinion in Allergy and Clinical Immunology in 2018 says that children with asthma are disproportionately affected by the air pollution because their airways become more easily inflamed or irritated due to common air pollutants. This impairs their lung function from an early age, which often leads to an increased risk of respiratory as well as pulmonary diseases during childhood itself.
Where the new study adds to our knowledge of childhood asthma is by indicating that air pollution not only worsens asthma symptoms in children but may be responsible for children developing the disease in the first place. It shows that genetics, as previously mentioned, is not the only risk factor for childhood asthma, but exposure to air pollution may also increase a child’s chances of getting their first asthma attack.
Small particulate matter and asthma onset in children
The new BMJ study was based in Denmark, where all Danish children born between 1997 and 2014 were included. The participants’ health status was followed in this nationwide case-control study to check for asthma onset and persistent wheezing from age one to 15.
The researchers found that while children whose parents had asthma were still more likely to develop the chronic disease, those who were exposed to higher levels of small particulate matter (PM 2.5) and nitrate pollution also had an increased risk of asthma onset. For every five micrograms per cubic metre increase in the concentration of these pollutants, the risk of asthma onset increased by 4-5 percent.
PM 2.5 clearly had the most robust connection with childhood asthma onset, especially due to the amount of oxidative stress, tissue damage and inflammation it causes. According to the Natural Resources Defense Council (NRDC), PM 2.5 comes primarily from combustion, so car engines (traffic), fireplaces, firecrackers, and coal- or natural-gas-powered plants are its major sources.
The BMJ study also noted that pollution levels in Denmark are much lower than in parts of central Europe, and yet these are the results of their nationwide study. In other areas with higher concentrations of PM 2.5 in the air, the rate of childhood asthma onset could, in fact, be much higher. This is study could have immense implications for nations like India, where PM 2.5 levels become particularly hazardous during the winter months every year due to crop burning, firecrackers, and other causes.
For more information, read our article on Asthma in children.
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