Occupational Lead Exposure among Lead Burners in a Copper Mining Company, Zambia

Abstract

Enlisted among the World Health Organisation’s (WHO) 10 chemicals of major public health concern and causing 0.6% of the global disease burden, lead exposure occurs through multiple routes. Downward lead exposure trends have been reported yet Zambian literature is scanty. This study characterised exposure among lead handlers at a Zambian copper mine by comparing external occupational exposure with the internal lead body burden. The study was University of the Witwatersrand (Wits) Medical - Human Research Ethics Committee (HREC), Tropical Diseases Research Centre (TDRC) - HREC, and Zambian National Health Research Authority (NHRA) approved. Historical (n=51) and current (n=39) blood lead internal exposure values, versus multi-route current external occupational exposure assessment was conducted. The samples in the external assessment were palmar wipes (n=53), surface wipes (n=27), breathing zone air (n=37), and room air (n=5) to determine lead concentration. Convenience sampling was done. South African National Accreditation System (SANAS) - accredited laboratories performed chemical analyses. Jeffrey’s Amazing Statistics Program (JASP) software was used with 5% Alpha level of significance with 95% Confidence Interval to perform statistical analysis. Descriptive tests, Test for normality, Chi-square, Kruskal-wallis, Student T, Analysis of Variance (ANOVA), and Bayesian analyses were done. Most of the data was not normally distributed. International reference standards were adopted since Zambia has none. The mean age of participants, all male, was 41 years with median exposure duration of 10 years. Mean blood lead was 1.61 units higher than the Occupational Health and Safety Administration’s (OSHA) recommended value (10 μg/dL). The personal and room air time weighted average (TWA) values were below the OSHA recommended value (0.05 mg/m3), National Institute for Occupational Safety and Health (NIOSH) recommended value (0.1 mg/m3), and American Conference of Governmental Industrial Hygienists (ACGIH) recommended value (0.05 mg/m3). No reference standards for dermal and ingestion routes were available. Health risk exposure assessment findings were: Dermal chronic daily intake (CDI = 6.76x10-11 mg/kg/day), Oral (CDI = 5.97x10-3 mg/kg/day), and Inhalation (CDI = 4.20x10-2 mg/kg/day). All pathways showed low risk for adverse health effects with hazard quotient (HQ) less than one. This study showed that the highest pathway contributing to lead exposure was inhalation although air sampling was within vi exposure limits. The internal body burden of lead was in exceedance of the recommended standard value but below the action and suspension levels following occupational exposure. Thus contributing to the field of Exposure science by considering all exposure pathways and routes of the entry of lead in an occupational setting. The findings of this study provide the basis for the development of intervention strategies to mitigate occupational lead exposure and prevent negative health impacts.