82 American Dental Association 56. Does fluoridated water harm the environment? Answer. No. Scientific evidence supports the fluoridation of public water supplies as safe for the environment and beneficial for people. Fact. Fluoride is naturally occurring in the environment and is the 13th most abundant element in the earth’s crust. It is found in naturally in all water sources as noted below.47 Rain — between 0.1 to 0.2 mg/L Streams and lakes — between 0.1 to 0.3 mg/L Groundwaters — between 0.1 to 10 mg/L Oceans and seawater — between 1.2 to 1.4 mg/L A comprehensive literature review published in 2004 revealed no negative environmental impacts as a result of water fluoridation.48 A 1990 study concluded that fluoridation has little or no impact on surrounding aquatic environment or soil.49 Historically, issues surrounding problems with fluoride and the environment have involved incidents related to serious industrial pollution or accidents.49 Under the Washington’s State Environmental Protection Act (SEPA), a study was conducted in Tacoma-Pierce County to investigate the environmental consequences of adding optimal levels of fluoride to drinking water. Noting that the amount of fluoride in the water does not reach levels that are harmful to plants or animals, the SEPA study concluded that there are “no probable significant adverse environmental impacts.”50 There is no evidence that the recommended level of fluoride in drinking water has any adverse effect on gardens, lawns or plants.50 Additional information regarding water fluoridation additives and engineering issues can be found on the CDC’s fluoridation website, “Water Operators and Engineers” at https://www.cdc.gov/fluoridation/ engineering/index.htm.