Eleven schools in Cape Town and ten schools in Johannesburg were surveyed. Following procurement of written, informed consent, a pre-structured questionnaire was administered to the parents/guardians of study children to obtain essential background and risk factor data. Venous blood samples were collected from children, and environmental samples taken for analysis of manganese content.
Questionnaire data indicated that the study populations in the two cities were socio-economically similar, with no evidence of differences in respect of type of home, proximity to busy roads, and type of cooking or heating fuel used. The mean blood manganese concentration amongst children in Cape Town equaled 6.89 (sd 3.47)μg/1; whilst in Johannesburg the mean level equaled 9.76 (sd 3.59)μg/l. These differences were highly significant (p < 0.001) even when taking account of clustering effects within schools, and adjusting for the confounding effect of population group. No additional confounding factors were found to approach statistical significance. Differences between the cities in respect of the manganese content of soil (p < 0.0007) and dust (p < 0.0071) were also statistically significant. Blood manganese levels were significantly associated with levels of manganese in dust. Adjusting for this, the difference between cities remained highly significant.
The study found statistically significant differences between the two cities in blood, dust and soil concentrations of manganese. The findings of the study may be used as a baseline against which to measure future changes in the blood manganese concentrations amongst first grade school children in the selected study settings. Further work is needed to identify and apportion the sources contributing to the concentrations of manganese measured in children's blood in the study.