Mortality study of chemical workers exposed to dioxins: follow-up 23 years after chemical plant closure

Objectives To examine the long-term effects of dioxin-exposure, particularly with regard to cancer mortality, in a follow-up 23 years after closure of the chemical plant (Hamburg, Germany).

Methods The study comprised all persons (1191 men/398 women) employed in the plant on a full-time basis for a minimum of 3 months between 1952 and 1984 when the plant was closed down. Mortality follow-up was performed for the period from 1952 up to the reference date of 31 December 2007. Subjects entered the cohort at the date of their first employment in the plant. We calculated standardised mortality ratios (SMRs) using the population of Hamburg as reference.

Results The vital status could be determined for 96.5% of the study group (1145 men and 389 women). For men, there was an increase in overall mortality (ICD-9 1–999) (SMR=1.14, 95% CI 1.06 to 1.23), all-cancer mortality (SMR=1.37, 95% CI 1.21 to 1.56) and specific mortality from respiratory cancer (ICD-9 161, 162, 163) (SMR=1.64, 95% CI 1.32 to 2.03), oesophageal cancer (ICD-9 150) (SMR=2.56, 95% CI 1.27 to 4.57), rectum cancer (ICD-9 154) (SMR=1.96, 95% CI 0.98 to 3.51), as well as diseases of the circulatory system (ICD-9 390–459) (SMR=1.16, 95% CI 1.02 to 1.31). For women, there was an increase in breast cancer mortality (ICD-9 174) (SMR=1.86, 95% CI 1.12 to 2.91).

Conclusions The results of this extended follow-up are consistent with those of previous analyses of the cohort and with those of other cohorts. Our findings support the carcinogenic effect of dioxin compounds.