Olfactory tract/bulb metal concentration in Manganese-exposed mineworkers

Luis F Gonzalez-Cuyar; Gill Nelson; Susan Searles Nielsen; Wendy W Dlamini; Amelia Keyser-Gibson; C Dirk Keene; Michael Paulsen; Susan R Criswell; Natalie Senini; Lianne Sheppard; Shar Samy; Christopher D Simpson; Marissa G Baker; Brad A Racette

doi:10.1016/j.neuro.2024.04.001

Olfactory tract/bulb metal concentration in Manganese-exposed mineworkers

Neurotoxicology. 2024 Apr 4:102:96-105. doi: 10.1016/j.neuro.2024.04.001. Online ahead of print.

Authors

Affiliations

¹ University of Washington, School of Medicine and Department of Laboratory Medicine and Pathology, Division of Neuropathology, 325 9th Ave, Seattle, WA 98104, USA. Electronic address: luisgonz@uw.edu.
² School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 27 St Andrews Rd, Parktown 2193, South Africa; Department of Neurology, Barrow Neurological Institute, 240 W Thomas Rd, Phoenix, AZ 85013, USA.
³ Department of Neurology, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA.
⁴ Department of Neurology, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA; Department of Epidemiology, School of Public Health, University of Washington, 3980 15th Ave NE, Seattle, WA 98195, USA.
⁵ University of Washington, School of Medicine and Department of Laboratory Medicine and Pathology, Division of Neuropathology, 325 9th Ave, Seattle, WA 98104, USA.
⁶ Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
⁷ Department of Neurology, Barrow Neurological Institute, 240 W Thomas Rd, Phoenix, AZ 85013, USA; Department of Neurology, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA.
⁸ Department of Neurology, Barrow Neurological Institute, 240 W Thomas Rd, Phoenix, AZ 85013, USA.
⁹ Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA; Department of Biostatistics, School of Public Health, University of Washington, 3980 15th Ave NE, Seattle, WA 98195, USA.
¹⁰ School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 27 St Andrews Rd, Parktown 2193, South Africa; Department of Neurology, Barrow Neurological Institute, 240 W Thomas Rd, Phoenix, AZ 85013, USA; Department of Neurology, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA.

PMID: 38582332
DOI: 10.1016/j.neuro.2024.04.001

Abstract

Background: Manganese (Mn) is an essential micronutrient as well as a well-established neurotoxicant. Occupational and environmental exposures may bypass homeostatic regulation and lead to increased systemic Mn levels. Translocation of ultrafine ambient airborne particles via nasal neuronal pathway to olfactory bulb and tract may be an important pathway by which Mn enters the central nervous system.

Objective: To measure olfactory tract/bulb tissue metal concentrations in Mn-exposed and non-exposed mineworkers.

Methods: Using inductively coupled plasma-mass spectrometry (ICP-MS), we measured and compared tissue metal concentrations in unilateral olfactory tracts/bulbs of 24 Mn-exposed and 17 non-exposed South African mineworkers. We used linear regression to investigate the association between cumulative Mn exposures and olfactory tract/bulb Mn concentration.

Results: The difference in mean olfactory tract/bulb Mn concentrations between Mn-exposed and non-Mn exposed mineworkers was 0.16 µg/g (95% CI -0.11, 0.42); but decreased to 0.09 µg/g (95% CI 0.004, 0.18) after exclusion of one influential observation. Olfactory tract/bulb metal concentration and cumulative Mn exposure suggested there may be a positive association; for each mg Mn/m³-year there was a 0.05 µg/g (95% CI 0.01, 0.08) greater olfactory tract/bulb Mn concentration overall, but -0.003 (95% CI -0.02, 0.02) when excluding the three influential observations. Recency of Mn exposure was not associated with olfactory tract/bulb Mn concentration.

Conclusions: Our findings suggest that Mn-exposed mineworkers might have higher olfactory tract/bulb tissue Mn concentrations than non-Mn exposed mineworkers, and that concentrations might depend more on cumulative dose than recency of exposure.

Keywords: ICP-MS; MRI; Manganese; Metals exposure; Mineworkers; Olfactory; South Africa.