Increased mortality from infectious pneumonia after occupational exposure to inorganic dust, metal fumes and chemicals

Our plain-English summary of Increased mortality from infectious pneumonia after occupational exposure to inorganic dust, metal fumes and chemicals, by K. Torén, I. Qvarfordt, I.A. Bergdahl, et al (Thorax, 2011).

The study

• Authors: K. Torén, I. Qvarfordt, I.A. Bergdahl, B. Järvholm
• Journal: Thorax
• Published: 2011;66(11):992-6
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: There are epidemiological studies indicating that exposure to metal fumes is a risk factor for infectious pneumonia. Whether occupational exposure to other agents, such as inorganic dust or chemicals, also increases the risk for infectious pneumonia is not clear. The aim of the present study was to elucidate whether occupational exposure to respiratory pollutants and irritants increases the risk for infectious pneumonia.

Design: Prospective cohort study. Setting Swedish male construction workers. Participants 320,143 male construction workers exposed to inorganic dust (asbestos, man-made mineral fibres, dust from cement, concrete and quartz), wood dust, metal fumes and chemicals (organic solvents, diisocyanates and epoxi resins) or unexposed. Main outcome measures The cohort was followed from 1971 to 2003 and the main outcome measures were mortality to infectious pneumonia, lobar pneumonia or pneumococcal pneumonia. RRs were obtained by the person-years method and from Poisson regression models, adjusting for baseline values of age and smoking habits.

Results: Among men aged 20-64 years there was increased mortality from infectious pneumonias among construction workers exposed to metal fumes (RR 2.31, 95% CI 1.35 to 3.95), inorganic dust (RR 1.87, 95% CI 1.22 to 2.87) and chemicals (RR 1.91, 95% CI 1.37 to 3.22). The mortality was also increased from both lobar pneumonia and pneumococcal pneumonia. Among men aged 65-84 years the occupational exposure to inorganic dust and chemicals was associated with slightly increased mortality from infectious pneumonia. Among groups with mutually exclusive exposures there was increased mortality from infectious pneumonias among construction workers exposed to inorganic dust, but not among those exposed to wood dust or chemicals. There were no cases among workers exposed only to metal fumes.

Conclusions: Our findings indicate that exposure to inorganic dust increases the mortality from infectious pneumonias, especially lobar pneumonia and pneumococcal pneumonia. The mechanism is unclear, but the effect may be mediated through induced airways inflammation.

In plain English

This Swedish prospective cohort study followed 320,143 male construction workers, including 79,305 unexposed referents, first examined between 1971 and 1993, for deaths until 31 December 2003. Exposures were assigned from each man's first job title, using 1970s estimates by industrial hygienists. Asbestos was grouped with cement, concrete, quartz and man-made mineral fibre dust as "inorganic dust". The article gives no separate asbestos result. There were 773 deaths from infectious pneumonia. Among men aged 20 to 64, compared with unexposed construction workers and adjusted for age and smoking, the risk ratio was 1.87 (95% CI 1.22 to 2.87) for inorganic dust, 2.31 (1.35 to 3.95) for metal fumes and 1.91 (1.37 to 3.22) for chemicals. Among men aged 65 to 84 the risk ratios were lower. Exposures overlapped heavily. In an analysis of non-overlapping exposure groups, inorganic dust was linked to higher mortality, but chemicals and wood dust were not. The metal-fumes-only group had no cases. The authors concluded that inorganic dust exposure increases mortality from infectious pneumonia. They noted that referents probably had some dust exposure and that alcohol use 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. Relative risks came from Poisson regression adjusted for age and smoking.
• Who was studied: 320,143 male Swedish construction workers, of whom 79,305 were unexposed referents. Medical examinations took place from 1971 to 1993 and follow-up ran to 31 December 2003. White-collar workers, foremen and women were excluded.
• Exposure: Exposure was assigned by a job-exposure matrix from the job title at the first health examination, based on 1970s estimates by industrial hygienists. There were four groups: inorganic dust (asbestos, cement dust, concrete dust, man-made mineral fibres or quartz), chemicals (organic solvents, epoxy resins or diisocyanates), metal fumes, and wood dust. Each worker was classed only as exposed or not exposed.
• Main results:
  • There were 773 deaths from infectious pneumonia in total; 628 of them occurred in men over 64.
  • Men aged 20 to 64, compared with unexposed referents: increased mortality from infectious pneumonia for metal fumes (RR 2.31, 95% CI 1.35 to 3.95), inorganic dust (RR 1.87, 95% CI 1.22 to 2.87) and chemicals (RR 1.91, 95% CI 1.37 to 3.22).
  • Men aged 20 to 64 exposed to inorganic dust: lobar pneumonia RR 3.37 (95% CI 1.32 to 8.57) and pneumococcal pneumonia RR 4.29 (95% CI 1.28 to 13.86). Only three unexposed referents in this age group died of pneumococcal pneumonia, so these estimates have low precision.
  • Men aged 65 to 84: risk ratios were lower. They were statistically significant only for inorganic dust (RR 1.36, 95% CI 1.09 to 1.68) and chemicals (RR 1.40, 95% CI 1.08 to 1.81). Metal fumes gave RR 1.16 (95% CI 0.82 to 1.62).
  • In groups with non-overlapping broad exposure categories (all ages 20 to 84), the inorganic dust group was associated with increased mortality from infectious pneumonia (RR 1.42, 95% CI 1.16 to 1.75). The chemicals group (RR 1.07, 0.50 to 2.29) and the wood dust group (RR 1.27, 0.92 to 1.76) were not. There were no cases among workers exposed only to metal fumes.
  • Smoking was also a risk factor. Current smokers aged 20 to 64 had RR 2.77 (95% CI 1.84 to 4.16) and current smokers aged 65 to 84 had RR 1.45 (95% CI 1.22 to 1.72).
• The authors' conclusion: The authors concluded that exposure to inorganic dust at construction sites increases mortality from infectious pneumonia. They wrote that the mechanism is unclear but may involve airway inflammation.
• Limitations the authors state:
  • Referents probably had some occupational exposure, because dust is present at most construction sites and only the first job title was used. The authors said this may cause the risks to be underestimated.
  • There was considerable overlap among exposures. Most workers exposed to metal fumes were also exposed to inorganic dust.
  • Smoking was recorded only at baseline and did not distinguish heavy from light smokers.
  • There were no data on alcohol consumption, so bias from alcohol abuse cannot be excluded.
  • Pneumonia recorded as the underlying cause of death may include some misclassified cases in the oldest age groups.
  • The analysis limited to never-smokers lacked statistical power.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Cohort Study, Habit, Inflammation.

Related studies

• Increased mortality in COPD among construction workers exposed to inorganic dust — I.A. Bergdahl, K. Torén, et al. (2004)
• Inorganic dust pneumonias: the metal-related parenchymal disorders — P. Kelleher, K. Pacheco, et al. (2000)
• Respiratory health of workers exposed to metal dusts and foundry fumes in a copper refinery — G. Ostiguy, C. Vaillancourt, et al. (1995)
• Round atelectasis as a complication of Legionnella pneumonia — R. Kuno, D.J. Bower, et al. (1994)
• Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries — I.M. Michalek, J.I. Martinsen, et al. (2019)
• The INTEROCC case-control study: risk of meningioma and occupational exposure to selected combustion products, dusts and other chemical agents — D.M. McElvenny, M. van Tongeren, et al. (2018)

Browse more research in Thorax, or return to medical research.