People with chronic obstructive pulmonary disease (COPD) tend to experience worsening symptoms at times when levels of pollution in their community are higher, a new U.S. study indicates.
“Our findings are consistent with a growing number of studies reporting adverse effects of community-level exposure to air pollution on respiratory symptoms among COPD patients,” researchers wrote.
The study, “Personal and community-level exposure to air pollution and daily changes in respiratory symptoms and oxygen saturation among adults with COPD,” was published in Hygiene and Environmental Health Advances.
Previous studies link pollution exposure to COPD risk and lower quality of life
These studies have generally assessed exposure to pollution over long time frames. There’s been much less research into how day-to-day changes in pollution levels might affect daily symptoms for people with COPD.
Now, a team of scientists in the U.S. conducted a small trial called the Study of Pollution and COPD Exacerbation (SPACE) to assess how personal and community exposure to air pollutants each affect daily COPD symptoms.
A total of 30 people diagnosed with COPD, all of whom were heavy former smokers, were recruited at Beth Israel Deaconess Medical Center in Boston. Their mean age was 71.1 years, and 80% of the participants were white, while 20% were Black. Most had a household income of less than $50,000, and fewer than one-third had attained at least a bachelor’s degree of education.
Over the course of a year, participants underwent four month-long periods of monitoring, one in each season.
During each month of monitoring, participants filled out daily questionnaires to report their respiratory symptoms, including breathing and bronchitis (airway inflammation) symptoms. Their blood oxygen levels were measured with a portable oximeter.
Taken together, these findings support the notion that outdoor gaseous and particulate pollutants can exacerbate daily respiratory symptoms in COPD patients.
Previous-day community-level pollutants were assessed with Boston-area stationary air quality monitors, while previous-day personal air pollution was collected through lightweight, portable air quality monitors.
The personal monitors “have the advantage of also measuring indoor air quality, where people actually spend most of their time, and may be able to offer a more individualized exposure assessment by capturing differences in exposure due to behaviors and housing characteristics,” the researchers wrote.
Analyzed air pollutants included two gases: ozone — which results from pollutants emitted from cars, power plants, refineries, and chemical plants — and nitrogen dioxide, which is derived mostly from the burning of fossil fuel. It also included fine particulate matter (PM2.5), particles less than 2.5 micrometers in diameter that consist of smoke, aerosols, soot, mold spores, dander, and the like.
Results showed that higher pollutant levels in the community were associated with worse day-to-day symptoms for patients. Specifically, increased community levels of ozone or PM2.5 were associated with significantly increased odds of worsening for breathing and bronchitis symptoms.
Higher community levels of nitrogen dioxide were associated with a higher risk of worsening for bronchitis symptoms, but not breathing symptoms.
In turn, levels of personal exposure to pollutants generally didn’t show a significant association with symptoms.
In fact, data suggested that higher personal exposure to PM2.5 was linked to less severe respiratory symptoms, including breathing symptoms. These findings are likely attributable to issues with the personal air quality monitors, the team noted, as these have less sensitivity to distinguish between different types of particles in the air and may become confused by household dust.
“While the personal monitors have been calibrated to stationary monitors, the measurements are more variable and sensitive to environmental and technical factors,” the researchers wrote.
Outdoor pollution ‘can exacerbate daily respiratory symptoms in COPD’
In addition, higher daily exposure to personal or community levels of nitrogen dioxide was associated with lower daily blood oxygen levels. However, this association reached statistical significance only with data from personal monitors.
“Personal and community-level exposure to PM2.5 and [ozone] were not associated with daily oxygen saturation,” the researchers wrote.
“In this study of former smokers with COPD living in an urban environment, there was a pattern of worsening respiratory symptoms associated with previous-day community-level exposure to [ozone and particulate matter] and worsening oxygenation associated with personal exposure to [nitrogen dioxide],” the team wrote.
“Taken together, these findings support the notion that outdoor gaseous and particulate pollutants can exacerbate daily respiratory symptoms in COPD patients,” they added.
The study was limited to a small group of former smokers in an urban environment, so the results may not be generalizable to other situations, the researchers note, and further research is needed to fully understand how personal-level pollution affects COPD.