Our study showed that provision of fluoride-safe drinking water supply within the government standard of 1.2 mg/l have significant effects on the control of dental fluorosis and skeletal fluorosis, and decreasing fluoride concentrations in urine in the areas with high fluoride in drinking water. Besides, this study also provided a scientific foundation for assessing the prevalence of fluorosis in drinking water. The present study also indicated that the prevalence rates of dental fluorosis in children aged 8–12 and skeletal fluorosis in adults were 50.44 percent and 10.81%, respectively, in FNB areas (the FNB areas covered the villages in the provinces where no fluoride-safe drinking water supply is provided, and the villages where fluoride-safe drinking water supply schemes were provided with the water fluoride concentrations in drinking water exceeding the government standard). On the basis of the outcomes of this study, it is estimated that 1.35 million of children aged from 8 to 12 having dental fluorosis and 3.15 million adults in the age groups of more than 16 years suffering from both dental fluorosis and skeletal fluorosis in FNB areas and in some FSB areas where the fluoride level in drinking water exceeded the government standard. These fluorosis patients were mainly distributed in the northeast, northwest and central geographic parts in China. Moreover, in these geographic areas, the endemic fluorosis is relatively more severe in the provinces of Heilongjiang, Inner Mongolia, Xinjiang, Gansu, Tianjin, Hebei, Henan, Jiangsu, Shandong, and Anhui than in other provinces. These provinces would be the priority areas when the fluoride-safe water supply schemes are provided in the future.
The relationships between levels of drinking water fluoride and urine fluoride, dental fluorosis and skeletal fluorosis have been reported in studies15–19
in Japan, Indian, Germany and South Africa. The results in the FNB areas in the present study were consistent with these former investigations that there were significantly higher prevalence rates of dental fluorosis,15–18
and higher urine fluoride concentrations21
in areas with high fluoride concentrations in drinking water. Excessive intake of fluoride can cause the dental fluorosis and skeletal fluorosis, even with severe dyskinesia, limb deformity and even paralysis.14
Fluoride can also damage the digestive, nervous, immune and urinary systems.25
Moreover, the fluoride can also damage the intelligence of children.26
Therefore, disruption or damage of these systems can have a wide range of effects on the body.
On the basis of the severe harmful effects of fluorosis on human beings, some measures should be taken to control the occurrence and progress of fluorosis. First, the effects of pharmaceutical intervention on dental fluorosis and skeletal fluorosis could not let us feel satisfied enough,28
and severe patients finally need to carry out surgery, which result was also indeterminate; second, because the bioavailability of fluoride is generally reduced in humans when consumed milk (decreased to 70%)29
or a calcium (decreased to 60%)-rich diet,30
it has been highly recommended that the inhabitants of fluoride-contaminated areas should incorporate calcium-rich foods in their routine diet. But such measures could not fundamentally solve such a problem, and it could be hard to implement in poverty areas. Therefore, changing the drinking water sources used for the inhabitants living in fluoride contaminated areas would be an appropriate and reasonable way for prevention and control of the fluorosis. In 1995, a study by Boyle et al19
in Gasp region, Quebec of Canada mentioned the well drilling should be in different deeps according to the F-levels in different groundwater layers through studying the relationships between the prevalence of fluorosis and F-levels in groundwater in different areas. And Boyle indicated that hydrogeochemists, hydrologists, health officials and environmental regulators should work closely together in order to efficiently eradicate the risk of skeletal fluorosis from drinking water associated with geological environments where such risks exist. Although some advices were proposed, with the exception of China,5–8
there were few relative reports in others countries on providing large-scale fluoride-safe water in the past many years. These studies5–8
in China reported the fluoride concentration in drinking water and urine, and the prevalence rate of dental fluorosis or skeletal fluorosis after the fluoride-safe drinking water supply schemes have been provided. However, most of the studies we mentioned above were carried out in one or several provinces not in the national scale, and the selected villages were seldom than the present study. In addition, these studies only reported several values of the fluoride concentration in drinking water and/or urine, and/or the prevalence rate of dental fluorosis and/or skeletal fluorosis, not including all of them. Furthermore, these above values were not compared between FNB and FSB areas, and the effects of fluoride-safe water supply on the prevalence of fluorosis had not been evaluated.
In China, the fluoride-safe drinking water supply schemes have been provided in high water fluoride areas for many years. Through years of cooperation between various agencies, such as water resources, geology and health, rich experience has been accumulated as basis on the implementation of this study. However, some issues were observed during the study period, such as problems of difficulty in locating low fluoride level of drinking water sources and/or proper lining of wells after those wells have been drilled and proper maintenance, supervision and operation of the fluoride-safe drinking water supply schemes. In addition, some of the fluoride-safe drinking water supply schemes were found to have fluoride concentration more than 1.2 mg/l. In fact, these ‘fluoride-safe’ drinking water supply schemes were no longer ‘fluoride-safe’ at all. In fact, these water schemes were providing ‘non-fluoride-safe’ drinking water, which is harmful to the residents’ health by inducing dental fluorosis and skeletal fluorosis. The fact was that before the fluoride-safe water supply schemes were provided, the local residents were drinking water from their own tube wells with various depths, and not all tube wells had high fluoride concentration (based on the geological formation). Therefore, it is extremely important to monitor the fluoride level in all fluoride-safe drinking water supply schemes by starting from identifying the water sources to operation and maintenance, and ensure that the fluoride level in these fluoride-safe water schemes meets the government standards, and to carry out the surveillance of the prevalence of fluorosis for cross checking of the fluoride concentrations in the fluoride-safe drinking water supply schemes for long-term sustainability of supplying the fluoride-safe drinking water in FSB areas for the prevention and control of endemic fluorosis.