Daily Archives: March 12, 2016

Mapping of drinking water fluoride levels, Karnataka, India

This study maps fluoride concentrations. Interpretation of the results is confounded by imposing the assumption that an “optimum” level of fluoride is necessary or somehow desirable. Once a belief such as this is institutionalized it is simply carried along by others as a presupposition even though no evidence to for this effect is presented (or can be presented).

Chowdhury CR, Shahnawaz K, Kumari D, Chowdhury A, Bedi R, Lynch E, Harding S. Spatial distribution mapping of drinking water fluoride levels in Karnataka, India: fluoride-related health effects. Perspectives in public health. 2016 Feb 3. pii: 1757913915626744.

OBJECTIVES: (1) To estimate the concentrations of fluoride in drinking water throughout different zones and districts of the state of Karnataka. (2) To investigate the variation of fluoride concentration in drinking water from different sources, and its relationships to daily temperature and rainfall status in the regional districts. (3) To develop an updated fluoride concentration intensity map of the state of Karnataka, and to evaluate these data in the context of fluoride-related health effects such as fluorosis and their prevalence.
MATERIALS AND METHODS: Aqueous standard solutions of 10, 100 and 1,000 ppm fluoride (F) were prepared with analytical grade Na+/F and a buffer; TISAB II was incorporated in both calibration standard and analysis solutions in order to remove the potentially interfering effects of trace metal ions. This analysis was performed using an ion-selective electrode (ISE), and mean determination readings for n = 5 samples collected at each Karnataka water source were recorded.
RESULTS: The F concentration in drinking water in Karnataka state was found to vary substantially, with the highest mean values recorded being in the north-eastern zone (1.61 ppm), and the lowest in the south-western one (only 0.41 ppm). Analysis of variance (ANOVA) demonstrated that there were very highly significant ‘between-zone’ and ‘between-districts-within-zones’ sources of variation (p < 10-5-10-9), results consistent with a substantial spatial variance of water source F levels within this state.
CONCLUSIONS: The southern part of Karnataka has low levels of F in its drinking water, and may require fluoridation treatment in order to mitigate for dental caries and further ailments related to fluoride deficiency. However, districts within the north-eastern region have contrastingly high levels of fluoride, an observation which has been linked to dental and skeletal fluorosis. This highlights a major requirement for interventional actions in order to ensure maintenance of the recommended range of fluoride concentrations (0.8-1.5 ppm) in Karnataka’s drinking water sources.

Competitive Adsorption of Fluoride and Natural Organic Matter

Mouelhi M, Giraudet S, Amrane A, Hamrouni B. Competitive adsorption of fluoride and natural organic matter onto activated alumina. Environmental technology 2016 Mar 7:1-11.

Natural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.