title: Nervous system effects of occupational manganese exposure on South African manganese mineworkers.
abstract: Occupational exposure to airborne manganese dust has been shown to produce adverse effects on the central nervous system. Four hundred and eighty-nine blue and white collar manganese mineworkers from South Africa were studied cross-sectionally to investigate the nervous system effects of medium to low occupational manganese exposures. The different facilities included underground mines, surface processing plants, and office locations. A job exposure matrix was constructed using routine occupational hygiene data. Exposure variables included years of service, a cumulative exposure index (CEI) and average intensity of exposure (AINT) across all jobs, and blood manganese. Endpoints included items from the Q16, WHO-NCTB, SPES, and Luria-Nebraska test batteries, and a brief clinical examination. Potential confounders and effect modifiers included age, level of education, past medical history including previous head injury, previous neurotoxic job exposures, tobacco use, alcohol use and home language. Associations were evaluated by multiple linear and logistic regression modeling. Average exposure intensity across all jobs was 0.21mg/m(3) manganese dust. Multivariate analyses showed that none of the symptom nor test results were associated with any measure of exposure including blood manganese, after adjustment for confounders. This relatively large null study indicates that manganese miners exposed on average across all jobs to MnO(2) at levels near the American Conference of Governmental Industrial Hygienists Threshold Limit Value (ACGIH TLV) are unlikely to have a subclinical neurotoxicity problem.
authors.affiliation: Occupational and Environmental Health Research Unit, School of Public Health and Primary Health Care, University of Cape Town, South Africa. myers@cormack.uct.ac.za
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Myers
authors.forename: Jim
authors.initials: J
authors.lastname: teWaterNaude
authors.forename: Markus
authors.initials: M
authors.lastname: Fourie
authors.forename: H B Abie
authors.initials: HB
authors.lastname: Zogoe
authors.forename: Inakshi
authors.initials: I
authors.lastname: Naik
authors.forename: Penny
authors.initials: P
authors.lastname: Theodorou
authors.forename: Halina
authors.initials: H
authors.lastname: Tassel
authors.forename: Aarti
authors.initials: A
authors.lastname: Daya
authors.forename: Mary Lou
authors.initials: ML
authors.lastname: Thompson
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D006801:Humans; D016014:Linear Models; D008345:Manganese / Q000097:blood*; D020149:Manganese Poisoning / Q000097:blood* / Q000453:epidemiology* / Q000523:psychology; D008875:Middle Aged; D008906:Mining / Q000706:statistics & numerical data*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D016273:Occupational Exposure / Q000706:statistics & numerical data*; D013019:South Africa / Q000453:epidemiology
chemical_list: D008345:Manganese