Several questions come to mind regarding this study. The concentration of Mn in Huai’an City area drinking water is an order of magnitude greater than the US secondary standard. A weak correlation with cancer incidence at such high concentrations is hypothesis generating – the plausibility of the assertion that Mn is related to cancer is not discussed. Mn does not occur in ground water (or the environment) by itself and the presence (co-occurrence) of other known cancer causing contaminants must be considered. This is especially the case in such an industrialized area. In general there are other contaminants of more concern than Mn but perhaps not for this particular population.
Zhang Q, Pan E, Liu L, Hu W, He Y, Xu Q, Liang C. Study on the Relationship between Manganese Concentrations in Rural Drinking Water and Incidence and Mortality Caused by Cancer in Huai’an City. BioMed Research International. 2014;2014:645056. doi: 10.1155/2014/645056. Epub 2014 Nov 3.
Background. Cancer is a significant disease burden in the world. Many studies showed that heavy metals or their compounds had connection with cancer. But the data conflicting about the relationship of manganese (Mn) to cancer are not enough. In this paper, the relationship was discussed between Mn concentrations in drinking water for rural residents and incidence and mortality caused by malignant tumors in Huai’an city.
Methods. A total of 158 water samples from 28 villages of 14 towns were, respectively, collected during periods of high flow and low flow in 3 counties of Huai’an city, along Chinese Huai’he River. The samples of deep groundwater, shallow groundwater, and surface water were simultaneously collected in all selected villages. Mn concentrations in all water samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS 7500a). The correlation analysis was used to study the relationship between the Mn concentration and cancer incidence and mortality.
Results. Mn concentrations detectable rate was 100% in all water samples. The mean concentration was 452.32 μg/L ± 507.76 μg/L. There was significant difference between the high flow period and low flow period (t = -5.23, P < 0.05) and also among deep groundwater, shallow groundwater, and surface water (F = 5.02, P < 0.05). The ratio of superscale of Mn was 75.32%. There was significant difference of Mn level between samples in the high flow period and low flow period (χ (2) = 45.62, P < 0.05) and also among deep groundwater, shallow groundwater, and surface water (χ (2) = 10.66, P < 0.05). And also we found that, during the low flow period, Mn concentration has positive correlation with cancer incidence and mortality; for a 1 μg/L increase in Mn concentration, there was a corresponding increase of 0.45/100000 new cancer cases and 0.35/100000 cancer deaths (P < 0.05).
Conclusions. In Huai’an city, the mean concentration of Mn in drinking water was very high. Mn concentration correlated with cancer incidence and mortality.
The paper is here (Open Access).