Occupational exposure to ultrafine particles and lung cancer in a population exposed to asbestos

Our plain-English summary of Occupational exposure to ultrafine particles and lung cancer in a population exposed to asbestos, by C. Rostello, C. Gramond, S. Audignon, et al (BMC Public Health, 2025).

The study

• Authors: C. Rostello, C. Gramond, S. Audignon, I. Thaon, P. Brochard, J. Benoist, A. Gislard, F. Laurent, C. Paris, P. Andujar, B. Clin, J.C. Pairon, F. Delva
• Journal: BMC Public Health
• Published: 2025;25(1):784
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Ultrafine particles are present in ever greater quantities in the workplace and only one epidemiological study to date has found an association with the occurrence of lung cancer.

Objective: To investigate the effect of occupational exposure to ultrafine particles on the risk of lung cancer.

Methods: The ARDCO is a surveillance program involving retiree workers who had been exposed to asbestos during their working life. Exposure to ultrafine particles over the complete lifetime occupational history was assessed using the French job exposure matrix MATPUF. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CI).

Results: There was no association between exposure to ultrafine particles and lung cancer after adjustment for smoking and exposure to asbestos and crystalline silica.

Conclusion: The findings do not indicate increased risks of lung cancer for UFP after adjustment for level of exposure to asbestos, crystalline silica, and smoking status.

Clinical Trial Number: Not applicable.

© 2025. The Author(s).

In plain English

This French cohort study examined whether on-the-job exposure to ultrafine particles (very small particles, for example from combustion, welding or sanding) was linked to lung cancer among men who had been exposed to asbestos at work. It included 12,530 unemployed or retired men from the ARDCO cohort, enrolled in 2003 to 2005, and tracked new lung cancers through national health insurance records until 1 July 2021. Industrial hygienists estimated each man's asbestos exposure. Ultrafine particle and crystalline silica exposure were estimated from job-exposure matrices, which are tables linking jobs to likely exposures. Most of the men (96.2%) were classed as exposed to ultrafine particles, and 502 lung cancers were recorded. After adjustment for smoking, asbestos and silica, no excess of lung cancer was identified with ultrafine particle exposure (hazard ratio 1.08, 95% CI 0.67–1.73). Results for specific particle families were similar. For wood particles the association approached, but did not reach, statistical significance (HR 1.16, 95% CI 0.96–1.40). The authors concluded that the findings do not indicate increased lung cancer risk from ultrafine particles after these adjustments. They noted that the matrix had no exposure intensity and that nearly all subjects were exposed.

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: Cohort study (follow-up of the French ARDCO cohort) using Cox proportional hazard models
• Who was studied: 12,530 men from the French ARDCO cohort of unemployed or retired workers previously exposed to asbestos. The cohort originally included 14,218 people from four French regions, enrolled 2003 to 2005, with women excluded. Lung cancer incidence was followed to 1 July 2021.
• Exposure: Lifetime occupational exposure to ultrafine particles (UFPs), overall and in seven chemical families, assessed with the MatPUF job-exposure matrix, which gives probability and frequency but not intensity. Asbestos exposure (fiber type not specified) was rated by industrial hygienists at four levels from 0.01 to 10 equivalent fibers/mL and combined into a cumulative exposure index. Crystalline silica was assessed with the Matgene job-exposure matrix.
• Main results:
  • Of the 12,530 men, 12,059 (96.2%) were classed as exposed to UFPs.
  • 502 lung cancers (4.0%) were recorded in the study population.
  • 18 incident lung cancers occurred in men not exposed to UFPs and 484 in men exposed to UFPs.
  • For any UFP exposure, the hazard ratio adjusted for smoking, asbestos and silica was 1.08 (95% CI 0.67–1.73), so no excess of lung cancer was identified.
  • For men exposed to wood UFPs, the adjusted hazard ratio was 1.16 (95% CI 0.96–1.40), which the authors described as approaching statistical significance.
  • For men exposed to 'other organic' UFPs (47 lung cancers), the unadjusted hazard ratio was 1.49 (95% CI 1.10–2.02). After adjustment it was 1.27 (95% CI 0.93–1.74).
  • Compared with non-smokers, current smokers had an adjusted hazard ratio for lung cancer of 4.53 (95% CI 3.19–6.43). The unadjusted figure was 4.56 (95% CI 3.22–6.47).
• The authors' conclusion: The authors concluded that the findings do not indicate increased risks of lung cancer from ultrafine particles after adjustment for level of exposure to asbestos, crystalline silica and smoking status.
• Limitations the authors state:
  • The job-exposure matrix does not capture differences in exposure between workers in the same occupation. The authors say this is likely to cause misclassification and a loss of statistical power.
  • The matrix had no information on exposure intensity, so a cumulative UFP dose could not be calculated. A frequency-weighted duration was used instead.
  • Exposure to UFPs in ambient (outdoor) air could not be taken into account.
  • Health insurance data may not capture every lung cancer case.
  • Smoking data were missing for more than 30% of subjects and were filled in statistically (imputed).
  • Because almost everyone was exposed to UFPs, the study had little ability to distinguish exposed from unexposed men.
  • Possible confounders were not evaluated, including welding fumes and radon.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Lung Cancer, Occupational History, Hazard Ratio, confidence interval, Crystalline.

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