• diisocyanate
• healthy worker effect
• methylene chloride
• mortality
• polyurethane

Sorahan and Nichols,¹ writing in this journal, incorrectly understate the strength of evidence for work related increased mortality among their cohort of production workers in the UK flexible polyurethane foam industry. Their study actually found “some” evidence for a work related increase in all-cause mortality, respiratory disease mortality, and lung cancer mortality in this exposure circumstance, especially taking into account the healthy worker effect.² We are concerned to correct this error, because the United Automobile, Aerospace and Agricultural Implement Workers of America (UAW) represents substantial numbers of workers exposed to this process, and the UK data provide the first evidence of a mortality hazard in this industry, in contrast to two previous, perhaps weaker studies.^3,4

The authors observed an all-cause standardised mortality ratio (SMR) among men of 107 (101 to 113), and a respiratory disease SMR of 120 (101 to 141). Increased mortality of similar magnitude from these causes was observed among the smaller number of women, and the SMRs for both genders combined were significantly increased. Raised SMRs for all-cause and respiratory disease mortality are hardly ever seen in occupational cohorts except for foundry and asbestos workers. Typically, the SMR for all-cause mortality is about 80, and the SMR for most cancer causes about 90 in the absence of exposure to a carcinogen at the site.⁵ We have observed SMRs for all-cause mortality as low as 60 in UAW vehicle assembly and stamping cohorts.⁶ We are surprised that these authors mentioned a deficit for all-causes in the abstract of their previous study of this cohort, …