Occupational exposure to particulate air pollution and mortality due to ischaemic heart disease and cerebrovascular disease

Our plain-English summary of Occupational exposure to particulate air pollution and mortality due to ischaemic heart disease and cerebrovascular disease, by K. Torén, I.A. Bergdahl, T. Nilsson, et al (Occupational and Environmental Medicine, 2007).

The study

• Authors: K. Torén, I.A. Bergdahl, T. Nilsson, B. Järvholm
• Journal: Occupational and Environmental Medicine
• Published: 2007;64(8):515-9
• Cited by: 94 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: A growing number of epidemiological studies are showing that ambient exposure to particulate matter air pollution is a risk factor for cardiovascular disease; however, whether occupational exposure increases this risk is not clear. The aim of the present study was to examine whether occupational exposure to particulate air pollution increases the risk for ischaemic heart disease and cerebrovascular disease.

Methods: The study population was a cohort of 176,309 occupationally exposed Swedish male construction workers and 71,778 unexposed male construction workers. The definition of exposure to inorganic dust (asbestos, man-made mineral fibres, dust from cement, concrete and quartz), wood dust, fumes (metal fumes, asphalt fumes and diesel exhaust) and gases and irritants (organic solvents and reactive chemicals) was based on a job-exposure matrix with focus on exposure in the mid-1970s. The cohort was followed from 1971 to 2002 with regard to mortality to ischaemic heart disease and cerebrovascular disease. Relative risks (RR) were obtained by the person-years method and from Poisson regression models adjusting for baseline values of blood pressure, body mass index, age and smoking habits.

Results: Any occupational particulate air pollution was associated with an increased risk for ischemic heart disease (RR 1.13, 95% CI 1.07 to 1.19), but there was no increased risk for cerebrovascular disease (RR 0.97, 95% CI 0.88 to 1.07). There was an increased risk for ischaemic heart disease and exposure to inorganic dust (RR 1.07, 95% CI 1.03 to 1.12) and exposure to fumes (RR 1.05, 95% CI 1.00 to 1.10), especially diesel exhaust (RR 1.18, 95% CI 1.13 to 1.24). There was no significantly increased risk for cerebrovascular disease and exposure to inorganic dust, fumes or wood dust.

Conclusions: Occupational exposure to particulate air pollution, especially diesel exhaust, among construction workers increases the risk for ischaemic heart disease.

In plain English

This Swedish cohort study compared 176,309 male construction workers whose jobs were judged to involve dust, fumes or gases with 71,778 construction workers in jobs judged unexposed. It tracked deaths from ischaemic heart disease and cerebrovascular disease from 1971 to the end of 2001. Exposure was assigned from the first recorded job title, using estimates made by industrial hygienists in the 1970s. Asbestos was counted only as part of an "inorganic dust" group, along with cement dust, concrete dust, man-made mineral fibres and quartz. No separate asbestos result was reported. After adjusting for age, smoking, body mass index and high blood pressure, any exposure was associated with higher ischaemic heart disease mortality (relative risk 1.13, 95% CI 1.07 to 1.19). It was not associated with higher cerebrovascular disease mortality (0.97, 0.88 to 1.07). For ischaemic heart disease, inorganic dust gave 1.07 (1.03 to 1.12). Diesel exhaust, analysed separately, gave 1.18 (1.13 to 1.24). The authors concluded that occupational exposure to dust, gases and fumes increased the risk for ischaemic heart disease. They noted that the control group probably had some dust exposure and that cholesterol was not measured.

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: Prospective cohort study using health-examination records linked to the national cause-of-death register, with an internal comparison group of unexposed construction workers
• Who was studied: Swedish male construction workers examined in a voluntary occupational health programme, 1971 to 1993. There were 176,309 exposed workers and 71,778 unexposed controls (white-collar workers excluded). Follow-up ran from 1 January 1971 at earliest to 31 December 2001.
• Exposure: Exposure was assigned through a job-exposure matrix based on the first recorded job title and focused on the mid-1970s. It was grouped as inorganic dust (asbestos, cement dust, concrete dust, man-made mineral fibres, quartz), gases and irritants (organic solvents, epoxy resins, diisocyanates), fumes (metal fumes, asphalt fumes, diesel exhaust) and wood dust. Each was classed as exposed or not exposed. Asbestos was not analysed separately.
• Main results:
  • In the Poisson regression model, workers with any occupational exposure to particulate air pollution had an increased risk of death from ischaemic heart disease: RR 1.13 (95% CI 1.07 to 1.19).
  • There was no increased risk of death from cerebrovascular disease among exposed workers in the Poisson model: RR 0.97 (95% CI 0.88 to 1.07).
  • In the Poisson model with the separate exposure groups and confounders, the risk for ischaemic heart disease remained raised for inorganic dust, RR 1.07 (95% CI 1.03 to 1.12), and for fumes, RR 1.05 (95% CI 1.00 to 1.10).
  • In the person-years analysis of the fume types, diesel exhaust was linked to increased ischaemic heart disease risk: RR 1.18 (95% CI 1.13 to 1.24). Metal fumes (RR 1.01, 0.95 to 1.08) and asphalt fumes (RR 1.12, 0.96 to 1.30) were not significantly increased.
  • Ischaemic heart disease risk was higher in men aged 20 to 59 years than in older men. For fumes, the RR was 1.28 (95% CI 1.17 to 1.39) at ages 20 to 59, compared with 1.08 (1.03 to 1.13) at ages 60 to 84.
  • Among exposed never-smokers, risks for ischaemic heart disease and cerebrovascular disease were slightly increased, but the confidence intervals included 1 (not statistically significant).
  • Wood dust was associated with ischaemic heart disease in the person-years analysis (RR 1.12, 1.04 to 1.20). That increase disappeared in the Poisson model (RR 1.01, 0.93 to 1.10), possibly because of overlap with fume exposure.
• The authors' conclusion: The authors concluded that occupational exposure to dust, gases and fumes increased the risk for ischaemic heart disease, but that there was no clearly increased risk for cerebrovascular disease.
• Limitations the authors state:
  • Workers in the control group probably had some particulate exposure, because dust is general at construction sites. The authors say this may cause risks to be underestimated.
  • Exposure was based only on the first recorded job title, and workers may later have changed occupation.
  • Smoking was not classified over time and did not distinguish heavy from light smokers.
  • There was no information on serum cholesterol at baseline, which could act as a confounder.
  • The job-exposure matrix had not been formally validated.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Relative Risk, Habit.

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