There is no good evidence of any adverse medical effects associated with the consumption of water with fluoride naturally or artificially added at a concentration of 0.5 – 1.0 mg / litre other than the increase in dental fluorosis. US studies in areas with natural fluoride levels of up to 8 mg / litre found no clinical evidence of harm. However there is clear evidence from India and China that skeletal fluorosis and an increased risk of bone fractures occur as a result of long-term excessive exposure to fluoride (total intakes of 14 mg fluoride per day), and evidence suggestive of an increased risk of bone effects at total intakes above about 6 mg fluoride per day.