Seven years of external control of fluoride levels in the public water supply in Bauru, São Paulo, Brazil

Fluoridation of the public water supplies is recognized as among the top ten public health achievements of the twentieth century. However, the positive aspects of this measure depend on the maintenance of fluoride concentrations within adequate levels. Objective To report the results of seven years of external control of the fluoride (F) concentrations in the public water supply in Bauru, SP, Brazil in an attempt to verify, on the basis of risk/benefit balance, whether the levels are appropriate. Material and Methods From March 2004 to February 2011, 60 samples were collected every month from the 19 supply sectors of the city, totaling 4,641 samples. F concentrations in water samples were determined in duplicate, using an ion-specific electrode (Orion 9609) coupled to a potentiometer after buffering with TISAB II. After the analysis, the samples were classified according to the best risk-benefit adjustment. Results Means (±standard deviation) of F concentrations ranged between 0.73±0.06 and 0.81±0.10 mg/L for the different sectors during the seven years. The individual values ranged between 0.03 and 2.63 mg/L. The percentages of the samples considered “low risk” for dental fluorosis development and of “maximum benefit” for dental caries prevention (0.55-0.84 mg F/L) in the first, second, third, fourth, fifth, sixth, and seventh years of the study were 82.0, 58.5, 37.4, 61.0, 89.9, 77.3, and 72.4%, respectively, and 69.0% for the entire period. Conclusions Fluctuations of F levels were found in the public water supply in Bauru during the seven years of evaluation. These results suggest that external monitoring of water fluoridation by an independent assessor should be implemented in cities where there is adjusted fluoridation. This measure should be continued in order to verify that fluoride levels are suitable and, if not, to provide support for the appropriate adjustments.

公共供水加氟被认为是20世纪十大公共卫生成就之一。然而，该措施的积极效果依赖于将氟化物（Fluoride）浓度维持在适宜水平。

目的 本研究旨在报告巴西圣保罗州鲍鲁市（Bauru, SP）公共供水系统中氟化物（F）浓度长达7年的外部管控结果，基于风险-收益平衡原则验证该浓度水平是否适宜。

材料与方法 2004年3月至2011年2月期间，每月从该市19个供水片区采集样本，共计4641份。水样中的氟化物浓度采用经TISAB II缓冲处理后的离子选择性电极（Orion 9609）配合电位计进行平行重复测定。分析完成后，依据最佳风险-收益匹配标准对样本进行分类。

结果 七年间各供水片区的氟化物浓度均值（±标准差）介于0.73±0.06至0.81±0.10 mg/L之间。单一样本的浓度范围为0.03~2.63 mg/L。研究第1至第7年中，符合“氟斑牙发生低风险”且“龋病预防效益最大化”（0.55~0.84 mg F/L）标准的样本占比分别为82.0%、58.5%、37.4%、61.0%、89.9%、77.3%及72.4%，全研究周期的占比为69.0%。

结论 本次七年评估期间，鲍鲁市公共供水系统的氟化物浓度存在波动。研究结果表明，在实施规范化加氟的城市中，应由独立评估机构开展供水加氟的外部监测工作。应持续推行该监测措施，以验证氟化物浓度是否适宜，若不适宜则为后续合理调整提供依据。