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Correspondence |

Air Pollution and Chronic Cough in ChinaAir Pollution and Chronic Cough in China FREE TO VIEW

Wenjun Mao, MD; Wei Xia, MD; Jingyu Chen, MD
Author and Funding Information

From the Department of Cardiothoracic Surgery (Drs Mao and Chen); and the Department of Intensive Care Unit (Dr Xia), Wuxi People’s Hospital, Nanjing Medical University.

Correspondence to: Wenjun Mao, MD, Division of Cardiothoracic Surgery, Wuxi People’s Hospital, No. 299, Qing Yang Rd, Wuxi City, Jiangsu, China 214023; e-mail: maowenjun1@126.com


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2013;144(1):362-363. doi:10.1378/chest.13-0611
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Published online
To the Editor:

In a recent issue of CHEST (March 2013), Lai et al1 demonstrated that cough variant asthma, upper airway cough syndrome, eosinophilic bronchitis, and atopic cough (AC) constituted the main causes of chronic cough across five regions in China, based on a prospective survey using a modified diagnostic algorithm. They also concluded that geography, seasonality, age, and sex were not related to the spectrum of chronic cough. We do agree with the authors’ viewpoint. However, of note, in developing countries like China one major concern with the environmental factors (haze) should be raised because indoor and outdoor pollutants can cause chronic cough; namely, exposure to pollutants, such as diesel exhaust, sulfur oxides, ozone, nitrogen oxides, and particulate matter, participates in the development of respiratory symptoms.2

Haze air pollution represents deterioration of the air quality, which is consistently associated with respiratory hospital admissions. Thurston et al3 indicated that haze contributed to 24% of respiratory admissions; a 30% increase in outpatient attendance due to haze-related conditions was also observed by Emmanuel4 after forest fires in Singapore.

In China, haze has become a predominant problem confronted by 1.3 billion people in recent years, especially during the Chinese New Year, when fine particles and gaseous pollutants are released into the atmosphere after intensive displays of fireworks and firecrackers. It seems that the greater the air pollution the higher the prevalence of patients admitted to clinics with chronic cough as the chief complaint. The harmful effect of haze on the lungs may be related to the potential mechanism that particulates sedimentate in the lung, leading to pulmonary damnification and inflammation formation and subsequent reconditioning of the lung. Particulate matter camouflaged in the haze, as a recent value of air quality guidelines for the protection of health, was gradually recognized as a pollutant with significant impact on the pathogenesis of respiratory disease, with evidence of induction of oxidative stress both in vitro5 and in vivo.6

It would be helpful if the authors could investigate the association between particulate matter and chronic cough, to avoid bias introduced by this confounding factor. In addition, 64 cases, accounting for approximately 8.4% of the cohort reported by Lai et al,1 were diagnosed with unexplained cough, for which haze including particulate matter may be considered as the main cause, incorporating their role in the pathogenesy of chronic cough. Furthermore, subgroup analysis adjusted for daily environmental and meteorologic data across various regions will be appreciated, so as to clarify the causality relationship between environment and chronic cough.

Although the four common causes of chronic cough in the article remain stable across the disparate regions (χ2 = 1.782, P > .05) and are in the majority among the potential etiologic factors,1 the comparison of cough variant asthma (χ2 =15.902, P = .003), upper airway cough syndrome (χ2 =12.772, P = .012), and eosinophilic bronchitis (χ2 =12.326, P = .015) across five regions showed statistical significance, with an overall proportion of 68.4%.1 Therefore, it is inaccurate to suggest that no association between geography and the spectrum of chronic cough was observed in China.

References

Lai K, Chen R, Lin J, et al. A prospective, multicenter survey on causes of chronic cough in China. Chest. 2013;143(3):613-620. [CrossRef] [PubMed]
 
Groneberg-Kloft B, Kraus T, Mark Av, Wagner U, Fischer A. Analysing the causes of chronic cough: relation to diesel exhaust, ozone, nitrogen oxides, sulphur oxides and other environmental factors. J Occup Med Toxicol. 2006;1:6. [CrossRef] [PubMed]
 
Thurston GD, Ito K, Hayes CG, Bates DV, Lippmann M. Respiratory hospital admissions and summertime haze air pollution in Toronto, Ontario: consideration of the role of acid aerosols. Environ Res. 1994;65(2):271-290. [CrossRef] [PubMed]
 
Emmanuel SC. Impact to lung health of haze from forest fires: the Singapore experience. Respirology. 2000;5(2):175-182. [CrossRef] [PubMed]
 
Choi JH, Kim JS, Kim YC, Kim YS, Chung NH, Cho MH. Comparative study of PM2.5 - and PM10 - induced oxidative stress in rat lung epithelial cells. J Vet Sci. 2004;5(1):11-18. [PubMed]
 
Kim K, Park EY, Lee KH, Park JD, Kim YD, Hong YC. Differential oxidative stress response in young children and the elderly following exposure to PM(2.5). Environ Health Prev Med. 2009;14(1):60-66. [CrossRef] [PubMed]
 

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References

Lai K, Chen R, Lin J, et al. A prospective, multicenter survey on causes of chronic cough in China. Chest. 2013;143(3):613-620. [CrossRef] [PubMed]
 
Groneberg-Kloft B, Kraus T, Mark Av, Wagner U, Fischer A. Analysing the causes of chronic cough: relation to diesel exhaust, ozone, nitrogen oxides, sulphur oxides and other environmental factors. J Occup Med Toxicol. 2006;1:6. [CrossRef] [PubMed]
 
Thurston GD, Ito K, Hayes CG, Bates DV, Lippmann M. Respiratory hospital admissions and summertime haze air pollution in Toronto, Ontario: consideration of the role of acid aerosols. Environ Res. 1994;65(2):271-290. [CrossRef] [PubMed]
 
Emmanuel SC. Impact to lung health of haze from forest fires: the Singapore experience. Respirology. 2000;5(2):175-182. [CrossRef] [PubMed]
 
Choi JH, Kim JS, Kim YC, Kim YS, Chung NH, Cho MH. Comparative study of PM2.5 - and PM10 - induced oxidative stress in rat lung epithelial cells. J Vet Sci. 2004;5(1):11-18. [PubMed]
 
Kim K, Park EY, Lee KH, Park JD, Kim YD, Hong YC. Differential oxidative stress response in young children and the elderly following exposure to PM(2.5). Environ Health Prev Med. 2009;14(1):60-66. [CrossRef] [PubMed]
 
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