265973 Examine the effect of fine-particulate air pollutant on asthma in the United States: A multilevel study

Monday, October 29, 2012

Tao Li, MD , Department of Health Services Research and Administration, College of Public Health, University of Nebraska Medical Center, Omaha, NE
Ge Lin, PhD , College of Public Health, University of Nebraska Medical Center, Omaha, NE
Background: The association between fine-particulate air pollutant (PM2.5) and health burden remains controversial. Few studies controlled for the confounding effects of climate while assessing the effects of PM2.5, and vice versa. Separating the individual and ecological effects also led to inconsistent findings. Our study was to close these gaps.

Methods: We used random-effect, multilevel logistic regression models to examine the effects of PM2.5 on asthma across the United States while controlling for climate and other potential risk factors at both individual and county levels. Individual-level variables were obtained from the 2009 Behavioral Risk Factor Surveillance System (BRFSS), including the outcome variable (yes/no) representing “current asthma”, and a final weight was assigned to each respondent. A total of 374,780 respondents (232,865 females) in 2,230 counties across the U.S. were involved. The county-level exposure of main interest was the 4-year (2006-2009) average of the 24-hour maximum PM2.5 concentration. We also calculated the 3-year (2000, 2005 and 2007) average of maximum and minimum temperature in warm and cold seasons, respectively. Other county-level control variables included race/ethnicity, education, unemployment, and poverty. Individual-level records were linked with county-level variables via county FIPS. All data were obtained from publicly accessible resources. Models were separated by genders and by seasons.

Results: The younger age-groups had higher vulnerability to asthma. After controlling for seasonal temperature and other risk factors at both levels, PM2.5 concentration showed negative odds ratios for both genders, but none was significant. Ceteris paribus, there was an inverse association between asthma risk and temperature in both warm seasons (OR: 0.913, 95%CI: 0.883, 0.943) and cold seasons (OR: 0.975, 95%CI: 0.959, 0.991).

Conclusions: After controlling for climate and other potential confounders at individual and county levels, PM2.5 does not exert significant effect on asthma. However, cold climate is significantly harmful. The younger population is more vulnerable.

Learning Areas:
Chronic disease management and prevention
Environmental health sciences
Public health or related public policy
Public health or related research

Learning Objectives:
Assess the effects of the fine-particulate air pollutant and climate on asthma. Demonstrate the importance of controlling for individual-level confounders in population-based studies on the association between environmental risk factors and health burden. Compare the vulnerability to asthma among different age groups.

Keywords: Air Pollutants, Climate

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I have a doctoral degree in medicine and have been focusing on cardiac-pulmonary diseases, especially asthma. I am now a 3rd-year Ph.D student in public health and still have strong interest in research on environmental health and asthma prevention. I have finished several studies on the effects of ambient air pollutants and climate change on asthma. I designed this study, collected and analyzed the data, and interpreted its results.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.