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Occup Environ Med. 2019 Sep;76(9):680-687. doi: 10.1136/oemed-2019-105744. Epub 2019 Jul 15.

Validity of retrospective occupational exposure estimates of lead and manganese in a case-control study.

Author information

Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, USA.
Rocky Mountain Center for Occupational and Environmental Health, Department of Family and Preventive Medicine, University of Utah, Salt Lake City, Utah, USA.
Westat Inc, Rockville, Maryland, USA.
Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, USA.
Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA.
Department of Epidemiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
Bureau of Public Health Statistics and Informatics, New Hampshire Department of Health and Human Services, Concord, New Hampshire, USA.
Maine Cancer Registry, Augusta, Maine, USA.
Vermont Department of Health, Burlington, Vermont, USA.



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.


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.


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.


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.


biological monitoring; lead; metals; retrospective exposure assessment


Conflict of interest statement

Competing interests: None declared.

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