This observational study links elevated levels of specific outdoor air pollutants in particular urban locations to distinct changes in the airways during asthma attacks not triggered by respiratory viruses.
Asthma is caused by chronic inflammation of the airways. During an asthma attack, the airway lining swells, muscles around the airways contract, and the airways produce extra mucus, substantially narrowing the space for air to move in and out of the lungs.
Children who live in low-income urban environments in the United States are at particularly high risk for attack-prone asthma. Asthma attacks provoked by respiratory virus infections have been studied extensively, but those that occur independently of such infections have not.
In the current study, researchers examined the relationship between air pollutant levels and asthma attacks occurring in the absence of a respiratory virus among 208 children ages 6 to 17 years who had attack-prone asthma and lived in low-income neighborhoods in cities.
Then the researchers validated the associations they found between air pollutant levels and non-viral asthma attacks in an independent cohort of 189 children ages 6 to 20 years with persistent asthma who also lived in low-income neighborhoods in four U.S. cities.
They followed the children prospectively for up to two respiratory illnesses or approximately six months, whichever came first. Each illness was classified as viral or non-viral and as involving an asthma attack or not.
Then matched each illness with air quality index values and levels of individual air pollutants recorded by the Environmental Protection Agency in the relevant city on the dates surrounding the illness.
Polluted Air Means More Asthma Attacks for Urban Kids
They found that asthma attacks had a non-viral cause in nearly 30% of children, two to three times the proportion seen in non-urban children. These attacks were associated with locally elevated levels of fine particulate matter and ozone in outdoor air.
The investigators linked changes in the expression of specific sets of genes that play a role in airway inflammation to elevated levels of these two pollutants by analyzing nasal cell samples obtained from the children during respiratory illnesses.
Some of the identified gene expression patterns suggest that unique biological pathways may be involved in non-viral asthma attacks.
Given the study findings, it will be important to develop and test different strategies to see if they prevent or reduce pollution-associated asthma attacks in urban children.
These strategies may include treatments designed to counteract the harmful effects of elevated levels of outdoor air pollutants on airway inflammatory responses linked to non-viral asthma attacks, and devices for personalized monitoring of local outdoor air pollutant levels to inform asthma management.
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