Objectives The validity of surrogate measures of retrospective occupational exposure in population-based epidemiological studies has rarely been evaluated. Using toenail samples as bioindicators of exposure, we assessed whether work tasks and expert assessments of occupational metal exposure obtained from personal interviews were associated with lead and manganese concentrations.
Methods We selected 609 controls from a case–control study of bladder cancer in New England who had held a job for ≥1 year 8–24 months prior to toenail collection. We evaluated associations between toenail metal concentrations and five tasks extracted from occupational questionnaires (grinding, painting, soldering, welding, working near engines) using linear regression models. For 139 subjects, we also evaluated associations between the toenail concentrations and exposure estimates from three experts.
Results We observed a 1.9-fold increase (95% CI 1.4 to 2.5) in toenail lead concentrations with painting and 1.4-fold increase (95% CI 1.1 to 1.7) in manganese concentrations with working around engines and handling fuel. We observed significant trends with increasing frequency of both activities. For lead, significant trends were observed with the ratings from all three experts. Their average ratings showed the strongest association, with subjects rated as possibly or probably exposed to lead having concentrations that were 2.0 and 2.5 times higher, respectively, than in unexposed subjects (ptrend <0.001). Expert estimates were only weakly associated with manganese toenail concentrations.
Conclusions Our findings support the ability of experts to identify broad contrasts in previous occupational exposure to lead. The stronger associations with task frequency and expert assessments support using refined exposure characterisation whenever possible.
- retrospective exposure assessment
- biological monitoring
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DTS and MCF co-supervised this work.
Contributors DB, KPC, MRK, GMMH, MS, AJ, SK and DTS are responsible for the New England Bladder Cancer Study, including subject recruitment, data collection, study management and ongoing analyses using study data. The analysis of toenail samples was led by BPJ. J-FS, JMR, SJL, PJD, PSA, MPP, SK, DTS and MCF designed the validation study. JMR, SJL, PRJ, DDZ and MCF conducted the exposure assessment. Statistical analyses were conducted by J-FS, JMR, PSA, SK, DTS and MCF. Drafting of the manuscript was performed by J-FS, JMR, DTS and MCF. All authors read draft manuscripts, contributed to the interpretation of findings and provided comments and revisions. All authors have read and approved the manuscript.
Funding This study was funded by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics (Z01 CP010122; Z01 CP010125). MRK was funded by the National Institute of Environmental Health Sciences Superfund Research Program (P42ES007373). The analysis of toenail samples was carried out at the Dartmouth Trace Element Core Facility, which was established by grants from the National Institute of Health (NIH) and National Institute of Environmental Health Sciences (NIEHS) Superfund Research Program (P42ES007373) and the Norris Cotton Cancer Center at Dartmouth Hitchcock Medical Center (P30CA023108).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Not required.
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