Abstract:

Background: Artisanal and small-scale gold mining (ASGM) is rapidly growing economic sector with about 550,000 active individuals and indirectly employing about 8 million persons in the north-western Tanzania. The sector uses rudimentary mining methods that contributes significantly to environmental destruction and contamination of natural habitat. Communities living in and around ASGM are exposed to various harmful chemical elements, most notably mercury, lead, arsenic, and cadmium from multiple exposure pathways potentially affecting the cognitive developmental outcome of the children living in such settings.

Objective: This study aimed at determining the association between postnatal individual children’s exposure to heavy metals and cognitive developmental outcomes among school children aged (3-9 years) born and living in ASGM areas in north-western Tanzania.

Methods: This was a cross-sectional follow-up study of the Mining and Health Cohort established in 2016/2017 in Geita District in northwestern Tanzanian. A sample size of 207 school aged children were recruited to examine their cognitive outcomes. Individual children’s chemical element levels were determined using dried blood sample (DBS) technique for cadmium, lead and mercury and spot urine for arsenic. Individual children cognitive outcome (cognitive abilities and academic excellence) was assessed using the Teachers/parents Ratings of Everyday Cognitive and Academic Abilities (PRECAA). Data analysis was performed using Stata version15 and association between individual children exposure and cognitive development outcomes of the study population was determined using modified poison regression.



Results: This study revealed that (35.7%) of the study participant were cognitively impaired while (64.3%) were not. Those with Arsenic (As) levels > 15(μg/l) had (71%) chances of being cognitively impaired (aPR= 1.71, 95% CI=1.42,3.56), Lead (Pb) > 35(μg/l) had 20% (aPR= 1.20, 95% CI=1.08,1.95) and Mercury (Hg) > 0.8(μg/l) had 45% (aPR= 1.45, 95% CI=1.10,3.59. Children born to ASGM mothers had 25% chance of being impaired (aPR= 1.25, 95% CI=1.06,1.68) and those who belong to fathers working in ASGM had 46% (aPR= 1.46, 95% CI=1.31,1.95)

Conclusion: The association between heavy metals exposure and cognitive impairment is very significant among study participants. The rates of reported impairment in cognitive ability are still high in the studied population. This calls for the need to design targeted interventions to increase the knowledge on the importance of reducing risk of exposure to heavy metals to the community and hence reduce the risk of cognitive impairment problems in children.

Key words: Artisanal, Gold Mining, postnatal Chemical exposure, Cognitive developmental, arsenic, mercury, lead, cadmium