There are contradictory reports on the prevalence of
bone fractures associated with long-term
fluoride exposure from
drinking water. The prevalence of
bone fracture in six rural areas of China and the exposure of
fluoride in
drinking water was investigated. The data including medical history and demographic information,
bone fractures,
fluoride content in
drinking water, physical activity, cigarette smoking, alcohol consumption and dietary intakes were collected. A retrospective epidemiological study by using the same design, method, quality control and the same questionnaire was conducted. A total of 8266 male and female over 50 years of age were divided into 6 groups by the
fluoride concentrations in
drinking water. The subjects in each group exposed to different levels of
fluoride (0.25-0.34, 0.58-0.73, 1.00-1.06, 1.45-2.19, 2.62-3.58 and 4.32-7.97 mg/L) were 1363, 1407, 1370, 1574, 1051 and 1501 respectively. It has been confirmed that
drinking water was the only major source of
fluoride exposure in the studied populations. The total
bone fracture rates were 7.41%, 6.40%, 5.11%, 6.04%, 6.09% and 7.40% in each group. Natural
bone fracture rates in each group were 3.01%, 2.21%, 1.31%, 1.65%, 1.43% and 3.66% respectively. The prevalence of
bone fracture and water
fluoride level appeared a U-shaped relationship. The prevalence of total
bone fracture and natural
bone fracture in the population with
fluoride 1.00-1.06 mg/L in
drinking water was the lowest, compared with the groups exposed to
fluoride higher than 4.32 mg/L and lower than 0.73 mg/L. The highest prevalence of hip fracture was in the group with higher water
fluoride (4.32-7.97 mg/L) exposure. In general, the prevalence of hip fracture was lower and stable up to 1.06 mg/L of
fluoride in
drinking water, and then it appeared to rise. Based on the data collected in this investigation, it is concluded that the long-term
fluoride exposure from
drinking water higher than 4.32 mg/L might increase the risk of overall fractures as well as
hip fractures. The risk of overall fractures and natural fractures might be lower while the water
fluoride level is at 1.00-1.06 mg/L, however, no protective benefits of
fluoride for the risk of hip fracture was observed.