Blood manganese concentrations among first-grade schoolchildren in two South African cities

This study involved the measurement of manganese concentrations in the blood of the total number of 814 of grade one schoolchildren (430 and 384 in Cape Town and Johannesburg, respectively), and in water supplies, soil, and classroom dust at a total number of 21 participating schools. The results indicated higher concentrations of manganese in school soil (P=0.0007) and dust (P=0.0071) samples from Johannesburg relative to Cape Town. Similarly, the mean blood manganese concentration in Johannesburg study subjects (9.80 μg/L, SD 3.59) was significantly higher than that in Cape Town study subjects (6.74 μg/L, SD 3.47), after allowing for the clustering effect within schools and adjusting for the confounding effect of population group (P<0.0001). The blood manganese levels of 4.2% and 12.5% of children in Cape Town and Johannesburg, respectively, equaled or exceeded 14 μg/L, the upper normal reference value specified by the Agency for Toxic Substances Disease Registry (ATSDR, 2000). Importantly, levels of manganese in blood were found to be significantly associated with concentrations of manganese in classroom dust at schools.