Children exposed to higher levels of fine particle pollution (PM2.5) are more likely to develop asthma and persistent wheezing, according to a new study published by the BMJ. The findings add to a growing collection of research that links air pollution to the onset of asthma.
The researchers also identified other risk factors for asthma, including genetics, prenatal exposure to smoking, and parents with low education and low income.
Fine particle pollution is primarily the result of power plants, motor vehicles, and domestic energy production. These particles are so microscopic in size that they can penetrate deep into the lungs and may even gain entry into the circulatory system.
While short term exposure to elevated levels of air pollution has been conclusively linked to the worsening of asthma symptoms, the consequences of long term exposure have remained unclear.
To investigate, a team of researchers in Denmark set out to identify pollution and family-related risk factors for the onset of asthma and persistent wheezing in children between the ages of one and 15.
The investigation was focused on more than three million Danish children born from 1997 to 2014. Among these individuals, 122,842 children were identified as having asthma and persistent wheezing at an average age of 1.9 years.
This data was linked to air quality measurements at the children’s home addresses, parental asthma, maternal smoking, parental education, and income.
The study revealed that higher levels of asthma and persistent wheezing were most strongly linked to parents with asthma and in children of mothers who smoked during pregnancy.
By contrast, asthma cases were found less frequently among children with parents who had higher educational status and income.
Children living in areas with high levels of fine particulate matter, nitrogen dioxide, and nitrate were found to have a greater chance of developing asthma. However, only the link between asthma and PM2.5 persisted across different models and after further sensitivity analyses.
Despite some study limitations, such as factors related to the children’s indoor environment, the research differs from previous studies in that it accounts for a large, diverse group of children across all social classes and ages.
The researchers said that further reductions in fine particle pollution may help to reduce the number of children who develop asthma and persistent wheezing in highly exposed populations.
The study is published in the journal The BMJ.