Vapor, dust, and smoke exposure in relation to adult-onset asthma and chronic respiratory symptoms: the Singapore Chinese Health Study

Our plain-English summary of Vapor, dust, and smoke exposure in relation to adult-onset asthma and chronic respiratory symptoms: the Singapore Chinese Health Study, by T.D. LeVan, W.P. Koh, H.P. Lee, et al (American Journal of Epidemiology, 2006).

The study

• Authors: T.D. LeVan, W.P. Koh, H.P. Lee, D. Koh, M.C. Yu, S.J. London
• Journal: American Journal of Epidemiology
• Published: 2006;163(12):1118-28
• Cited by: 70 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Occupational factors contribute to a significant fraction of respiratory disease and symptoms. The authors evaluated the role of occupational exposures in asthma, chronic bronchitis, and respiratory symptoms in the Singapore Chinese Health Study, a population-based cohort of adults aged 45-74 years at enrollment in 1993-1998. Information on occupations and occupational exposures was collected at enrollment for 52,325 subjects for whom respiratory outcomes were obtained via follow-up interviews in 1999-2004. Exposure to dusts from cotton, wood, metal, minerals, and/or asbestos was associated with nonchronic cough and/or phlegm (odds ratio (OR) = 1.19, 95% confidence interval (CI): 1.08, 1.30), chronic bronchitis (OR = 1.26, 95% CI: 1.01, 1.57), and adult-onset asthma (OR = 1.14, 95% CI: 1.00, 1.30). Cotton dust was the major contributor to respiratory symptoms. Vapor exposure from chemical solvents, dyes, cooling oils, paints, wood preservatives, and/or pesticides was associated with nonchronic cough or phlegm (OR = 1.14, 95% CI: 1.03, 1.27), chronic dry cough (OR = 1.55, 95% CI: 1.19, 2.01), and adult-onset asthma (OR = 1.34, 95% CI: 1.15, 1.56). Chemical solvents, cooling oils, and pesticides were the major contributors to respiratory symptoms. These data support the role of occupational exposures in the etiology of respiratory illness in a population-based cohort in Singapore with a low prevalence of atopic illness.

In plain English

This study used the Singapore Chinese Health Study, a population-based cohort of Chinese adults aged 45 to 74 who enrolled in 1993 to 1998. At enrollment, participants said whether they had been exposed at work, in a job lasting a year or longer, to various dusts, smokes and vapors. Respiratory outcomes were collected by telephone in 1999 to 2004 for 52,325 people. Asbestos was not analyzed on its own. It was counted within 'mineral dust', which was part of a combined dust group with cotton, wood and metal dust. Combined dust exposure was associated with nonchronic cough and/or phlegm (odds ratio 1.19, 95% CI 1.08 to 1.30), chronic bronchitis (1.26, 1.01 to 1.57) and adult-onset asthma (1.14, 1.00 to 1.30). Cotton dust showed the strongest dust association. For mineral dust including asbestos, odds ratios ranged from 1.02 to 1.16, and every confidence interval included 1. The authors noted that few subjects were exposed to these dusts, so the study had limited power to examine them. Vapor exposure was associated with chronic dry cough (1.55, 1.19 to 2.01) and adult-onset asthma (1.34, 1.15 to 1.56). The authors concluded that the data support a role for occupational exposures in respiratory illness, while noting that the effects were modest.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population-based prospective cohort study: occupational exposures reported at baseline, respiratory outcomes reported at follow-up
• Who was studied: Men and women of Chinese ethnicity in Singapore, aged 45-74, enrolled 1993-1998. 52,325 completed a follow-up telephone interview in 1999-2004. The referent group was 45,104 people with no cough, phlegm or asthma.
• Exposure: Self-reported exposure in a job lasting 1 year or longer to dust (cotton, wood, metal, or mineral dust including asbestos), smoke (welding, coal, wood, other) or vapors (solvents, dyes, oils, paints, wood preservatives, pesticides). Asbestos was grouped within mineral dust and not analyzed separately.
• Main results:
  • Combined dust exposure (cotton, wood, metal, minerals, asbestos) was associated with nonchronic cough and/or phlegm (OR 1.19, 95% CI 1.08, 1.30), chronic bronchitis (OR 1.26, 95% CI 1.01, 1.57) and adult-onset asthma (OR 1.14, 95% CI 1.00, 1.30).
  • Mineral dust (which includes asbestos), 3,135 exposed in the referent group (Table 4). Odds ratios: nonchronic cough or phlegm 1.08 (0.94, 1.23); chronic phlegm 1.11 (0.93, 1.32); chronic dry cough 1.06 (0.73, 1.53); chronic bronchitis 1.02 (0.73, 1.42); adult-onset asthma 1.16 (0.95, 1.43). All intervals include 1.
  • Cotton dust exposure was associated with nonchronic cough or phlegm (OR 1.40, 95% CI 1.19, 1.64), chronic phlegm (OR 1.36, 95% CI 1.09, 1.69) and chronic bronchitis (OR 1.71, 95% CI 1.13, 2.60).
  • Vapor exposure was associated with nonchronic cough and/or phlegm (OR 1.15, 95% CI 1.03, 1.27), chronic dry cough (OR 1.55, 95% CI 1.19, 2.01) and adult-onset asthma (OR 1.34, 95% CI 1.15, 1.56).
  • Smoke exposure was associated with nonchronic cough or phlegm (OR 1.12, 95% CI 1.01, 1.25).
  • For chronic dry cough, the effects of dust, smoke and vapor were greater in nonsmokers than in smokers (p for interaction less than 0.04).
  • Occupational pesticide exposure was associated with adult-onset asthma (OR 1.69, 95% CI 1.13, 2.52).
• The authors' conclusion: The authors concluded that the data support a role for occupational exposures in physician-diagnosed adult-onset asthma, chronic bronchitis symptoms, chronic dry cough or phlegm, and nonchronic cough and/or phlegm.
• Limitations the authors state:
  • Few subjects were exposed to wood, metal or mineral dust, so the study was not well powered to examine these exposures.
  • There was no information on the timing of exposure relative to when symptoms began.
  • The effects were modest, and unknown biases may contribute to modest associations.
  • Self-reported exposure to cutting, cooling or lubricating oils was likely subject to a high level of misclassification.
  • The type of solvent used was not asked.
  • 5,339 subjects died before the follow-up interview, creating a possibility of bias.
  • People with COPD but no symptoms may have been included in the referent group, which would tend to weaken associations.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Odds Ratio, confidence interval, Etiology.

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