Long-term dynamics of death rates of emphysema, asthma, and pneumonia and improving air quality

Abstract

Background

The respiratory tract is a major target of exposure to air pollutants, and respiratory diseases are associated with both short- and long-term exposures. We hypothesized that improved air quality in North Carolina was associated with reduced rates of death from respiratory diseases in local populations.

Materials and methods

We analyzed the trends of emphysema, asthma, and pneumonia mortality and changes of the levels of ozone, sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and particulate matters (PM_2.5 and PM₁₀) using monthly data measurements from air-monitoring stations in North Carolina in 1993–2010. The log-linear model was used to evaluate associations between air-pollutant levels and age-adjusted death rates (per 100,000 of population) calculated for 5-year age-groups and for standard 2000 North Carolina population. The studied associations were adjusted by age group-specific smoking prevalence and seasonal fluctuations of disease-specific respiratory deaths.

Results

Decline in emphysema deaths was associated with decreasing levels of SO₂ and CO in the air, decline in asthma deaths–with lower SO₂, CO, and PM₁₀ levels, and decline in pneumonia deaths–with lower levels of SO₂. Sensitivity analyses were performed to study potential effects of the change from International Classification of Diseases (ICD)-9 to ICD-10 codes, the effects of air pollutants on mortality during summer and winter, the impact of approach when only the underlying causes of deaths were used, and when mortality and air-quality data were analyzed on the county level. In each case, the results of sensitivity analyses demonstrated stability. The importance of analysis of pneumonia as an underlying cause of death was also highlighted.

Conclusion

Significant associations were observed between decreasing death rates of emphysema, asthma, and pneumonia and decreases in levels of ambient air pollutants in North Carolina.

Keywords:

• chronic obstructive pulmonary disease
• sulfur dioxide
• carbon monoxide
• nitrogen dioxide
• particulate matter

Supplementary material

Table S1 Results of the sensitivity analysis

Acknowledgments

The authors thank Fred and Alice Stanback for supporting this study with a philanthropic donation to the Duke Cancer Center.

Author contributions

JK, WGR, and HKL developed the concept behind the study; JK and IA designed the study and carried out the data analysis with help from APA, SH, and HKL; JK wrote the paper with help from IA, and SH; APA, WGR, and HKL provided critical reviews of the manuscript. All authors have read and approved the final manuscript.

Disclosure

The authors report no competing conflicts of interest in this work.