Research capacity development in South African manganese mines to bridge exposure and neuropathologic outcomes

Abstract

Manganese (Mn) is a common occupational exposure worldwide. Recent studies indicate clinical and imaging evidence of neurotoxicity in chronically exposed workers. The pathologic significance of these findings is unclear. South Africa produces over 80% of the world's Mn from mines from a desert region in the Northern Cape Province. An autopsy program at the National Institute for Occupational Health (NIOH) in South Africa has provided compensation to families for mining-related lung diseases for almost 100 years. Building on this, we implemented a brain autopsy program to investigate the feasibility of obtaining brains from South African Mn miners and non-exposed reference miners to investigate neuropathologic consequences of chronic Mn exposure. Employing an experienced occupational health nurse, we identified deceased miners within 100 square km of the Mn mines. The nurse was notified of any Mn (case) or other (reference) miner or ex-miner death by local medical practitioners, occupational health and mine physicians, and community members, and families were approached for consent to remove the brains in addition to the cardio-respiratory organs. Families of deceased miners who had an autopsy at the NIOH in Johannesburg were also approached. To confirm exposure in Mn miners, mean pallidal indices were compared between Mn miners and non-exposed reference miners. Sixty-eight potential brain donors were identified; we obtained consent from the families to remove 51 (75%). The mean autopsy interval was seven days. With optimized fixation methods, the tissue quality of the brains for gross and regular microscopic examination was excellent. Ex vivo MRI demonstrated increased pallidal index in Mn miners compared to reference miners. We conclude that obtaining brain tissue from deceased miners in South Africa is highly successful with only a modest investment in local infrastructure. Tissue quality was excellent and should be ideal to investigate the neuropathologic consequences of chronic occupational Mn exposure.