Uncontrolled Asthma Linked to Long-Term Air Pollution Exposure


Air pollution can make respiratory symptoms, like those associated with asthma, much worse, but is the reverse true as well? Yes, according to a new study, which suggests long-term exposure to air pollution can make it more difficult to control asthma.

Asthma and air pollution—an unhealthy mix

The latest data (2011) from the Centers for Disease Control and Prevention (CDC) is not promising: about 10 percent of children and 8 percent of adults had asthma in 2009, which is 1 in 12 people compared with 1 in 14 in 2001. Between 2001 and 2009, the number of people diagnosed with asthma increased by 4.3 million.

The link between air pollution and asthma has received a considerable amount of attention, and now a new French study introduces more findings. A research team set out to evaluate the effect of long-term exposure to air pollution on control of asthma.

The subjects included 481 adults with active asthma who had participated in the Epidemiological study on the Genetics and Environment of Asthma (EGEA), first conducted in 1995-95. The adults in this study were part of a follow-up to EGEA and completed a questionnaire on their respiratory health between 2003 and 2007.


Using data from the French Institute of the Environment, the investigators calculated the levels of nitrous oxide, ozone, and particulate matter each subject was exposed to at their home over one year. Degree of asthma control was determined according to each participant’s symptoms, number of asthma attacks, and lung function.

Of the 481 subjects for which air pollutant data was available, 44 percent had controlled, 29 percent had partly controlled, and 26 percent and uncontrolled asthma. Asthma was uncontrolled more often in women and in older participants.

Investigators determined that long-term exposure to ozone and particulate matter was strongly associated with decreased asthma control. Specifically, long-term exposure to ozone was associated with a 69 percent increased risk of uncontrolled asthma, and exposure to particulate matter increased the risk by 35 percent.

The study’s authors called their results “robust,” and noted that the study is the first to demonstrate that long-term exposure to air pollution is associated with uncontrolled asthma.

Centers for Disease Control and Prevention
Jacquemin B et al. Epidemiology and Community Health 2011; doi: 10.1136/jech.2010.130229