Cancer morbidity in Swedish dry-cleaners and laundry workers: historically prospective cohort study

PURPOSE: Despite decades of experimental and observational studies, the carcinogenic risks to humans associated with occupational exposure to perchloroethylene (PER) remain uncertain. The aims of the present study were to further examine the possible associations. METHODS: A national cohort of dry-cleaning and laundry workers (n = 10,389) assembled in 1984 was followed up for new cases of cancer by matching with the Swedish cancer register from 1985 to 2006 (inclusive), and the results were compared with expected frequencies derived from national reference data. RESULTS: Follow-up was complete for 90.9% of the cohort (2,810 men, 6,630 women). The overall standardised cancer incidence ratio (SIR) for all subjects was close to unity (SIR 0.96; 95% confidence interval (CI) 0.91–1.02) with a slightly more favourable outcome in women (SIR 0.91; 95% CI 0.85–0.98) than in men (SIR 1.10; 95% CI 0.99–1.23). Significantly elevated rates of lung cancer (SIR 1.45; 95% CI 1.03–1.98) and non-Hodgkin’s lymphoma (SIR 2.05; 95% CI 1.30–3.07) were seen in men, but for both types of cancer, the point estimates were similar in genuine laundry workers and dry-cleaners exposed to PER, respectively. There was no significant excess of cancer of the oesophagus, larynx, uterine cervix, liver, kidney or urinary bladder. CONCLUSIONS: The absence of individual or collective data on PER exposure from participating dry-cleaning shops and laundries involved and limited information on exposure time hampered the risk assessment related to PER. However, no clear association between PER exposure and subsequent cancer morbidity in the workers was evident from this historically prospective cohort.