Incidence of urolithiasis and composition of household water in southern Finland.

High concentration of iron (greater than or equal to 1.5 mg/l) and high total hardness of household water (greater than or equal to 7.0 dH0) in residence community were associated with low hospital admission rate for urolithiasis in a population of about 1.2 million during one year. The incidence of ureteral and renal stone did not vary according to natural fluoride content of drinking water, but it was lower in a city with fluoridated water than in a reference city.