A large prospective study found an elevated risk that did not quite reach statistical significance, but found a strong dose–response relationship with total years of exposure. 1 Two studies found no significant association, 1 2 although one found a suggestion of elevated risk among the very highly exposed. 2 We examine here the association of ALS mortality with job-related formaldehyde exposure in the National Longitudinal Mortality Study (NLMS), a US-representative cohort with occupation data collected prospectively.
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