Exposure to increased levels of air pollution can lead to the development of asthma in children, a new study suggests.
The research, published in The BMJ, also found that asthma was more likely to be found among children whose parents have the condition, or where the mother smoked during pregnancy.
Reduction in pollution levels in areas of poor air quality may reduce the number of children who suffer from the disease, the study added.
Children from wealthier backgrounds and those whose parents had a high level of educational achievement were less likely to have the condition.
For the study, researchers examined data on Danish children born between 1997 and 2014.
They were then tracked, some until they were 15 years old, to see whether or not they developed asthma or a persistent wheeze.
A total of 122,842 children were identified as having developed asthma or a wheeze.
Youngsters exposed to higher levels of air pollution – measured through particulate matter or PM2.5 – were more likely to have asthma or a persistent wheeze.
The authors from Denmark wrote: “The findings of this study suggest that children exposed to higher levels of PM2.5 are more likely to develop asthma and persistent wheezing than children who are not exposed.
“Other risk factors associated with these outcomes were parental asthma, parental education, and maternal smoking during pregnancy.”
They added: “The results suggest that further reductions in PM2.5 might help to reduce the number of children who develop asthma and persistent wheezing in highly exposed populations.”
Commenting on the study, Zak Bond, policy officer at Asthma UK and the British Lung Foundation, said: “This is an interesting study, and while we require further substantiation, it clearly demonstrates the importance of tackling dirty air to protect our health.
“Fine particulate matter (PM2.5) is the most worrying type of pollution for lung health, and disproportionately impacts certain groups, including the very young, older people and people with lung conditions such as asthma.
“Our recent statistics show that one in four people with asthma in the UK noticed their symptoms improved during lockdown, likely as a result of the fall in air pollution levels.
“Asthma UK and the British Lung Foundation are campaigning for the government to back a strong new legal limit for PM2.5, in line with World Health Organisation guidelines, in the Environment Bill. It is time to reduce air pollution so everyone can breathe clean air with healthy lungs.”
The Danish study comes as an international team of scientists announced findings that could help develop a new treatment for asthma and chronic obstructive pulmonary disease (COPD).
The breakthrough, published in the journal Science Translational Medicine, identifies a class of drugs that reverse the symptoms.
Researchers also found the same drugs, when applied to lung samples obtained from human donors, showed effects similar to those seen in the animal models.
Scientists believe these combined findings offer new hope these drugs could provide new medicines for human inflammatory lung diseases.
Andrew Tobin, professor of molecular pharmacology at the University of Glasgow, said: “It was indeed a surprise to find that by targeting a protein that up to now has been thought of as being activated by fish oils in our diet we were able to relax airway muscle and prevent inflammation.
“We are optimistic that we can extend our findings and develop a new drug treatment of asthma and COPD.”
The drugs used by the Glasgow team work through a mechanism that is distinct from currently prescribed medicines for asthma and COPD.
Findings describe a route to alternative treatments for patients suffering from severe forms of the conditions, that are not controlled by current frontline treatments.
The new approach is centred on the activation of a protein that has previously been known to respond to fats contained in our diet.
Additional reporting by PA
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