Exhaled carbon monoxide and its associations with smoking, indoor household air pollution and chronic respiratory diseases among 512,000 Chinese adults

China Kadoorie Biobank (CKB) collaborative group

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BACKGROUND: Exhaled carbon monoxide (COex) level is positively associated with tobacco smoking and exposure to smoke from biomass/coal burning. Relatively little is known about its determinants in China despite the population having a high prevalence of smoking and use of biomass/coal.

METHODS: The China Kadoorie Biobank includes 512,000 participants aged 30-79 years recruited from 10 diverse regions. We used linear regression and logistic regression methods to assess the associations of COex level with smoking, exposures to indoor household air pollution and prevalent chronic respiratory conditions among never smokers, both overall and by seasons, regions and smoking status.

RESULTS: The overall COex level (ppm) was much higher in current smokers than in never smokers (men: 11.5 vs 3.7; women: 9.3 vs 3.2). Among current smokers, it was higher among those who smoked more and inhaled more deeply. Among never smokers, mean COex was positively associated with levels of exposures to passive smoking and to biomass/coal burning, especially in rural areas and during winter. The odds ratios (OR) and 95% confidence interval (CI) of air flow obstruction (FEV1/FVC ratio<0.7) for never smokers with COex at 7-14 and ≥14 ppm, compared with those having COex<7, were 1.38 (1.31-1.45) and 1.65 (1.52-1.80), respectively (Ptrend<0.001). Prevalence of other self-reported chronic respiratory conditions was also higher among people with elevated COex (P<0.05).

CONCLUSION: In adult Chinese, COex can be used as a biomarker for assessing current smoking and overall exposure to indoor household air pollution in combination with questionnaires.

Original languageEnglish
Pages (from-to)1464-1475
Number of pages12
JournalInternational Journal of Epidemiology
Issue number5
Early online date20 Sept 2013
Publication statusPublished - Oct 2013
Externally publishedYes

Bibliographical note

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which
permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.


  • Adult
  • Aged
  • Air Pollution, Indoor/statistics & numerical data
  • Biomass
  • Breath Tests
  • Carbon Monoxide/analysis
  • China/epidemiology
  • Coal
  • Cough/epidemiology
  • Environmental Exposure/statistics & numerical data
  • Exhalation
  • Female
  • Heating/statistics & numerical data
  • Humans
  • Linear Models
  • Logistic Models
  • Male
  • Middle Aged
  • Odds Ratio
  • Pulmonary Disease, Chronic Obstructive/epidemiology
  • Respiration Disorders/epidemiology
  • Rural Population/statistics & numerical data
  • Seasons
  • Smoke
  • Smoking/epidemiology
  • Tobacco Products/statistics & numerical data
  • Tobacco Smoke Pollution/statistics & numerical data
  • Tuberculosis, Pulmonary/epidemiology


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