The health effects of fluoride have been identified in many animal and human studies, and have been considered in major systematic reviews, in particular the York Review in the UK and the National Research Council in the USA. Both of these reviews noted the lack of evidence to assure safety and stressed that more research needed to be done, particularly in areas such as cancer, thyroid diseases and the brain. The NRC review identified fluoride as an endocrine (hormone) disruptor in small doses and found thyroid effects at levels below those used in water fluoridation. Subsequently, fluoride has been classified as a developmental neurotoxin, and has been associated with osteosarcoma, reduced IQ, thyroid disease and ADHD. While health authorities insist that there is no danger to health at the levels used in water fluoridation (up to 1ppm), there is no control of or monitoring of the levels of fluoride in individuals. .
Fluoride is ingested from food and beverages, toothpaste, dental products, and other sources in addition to water, and the total dietary intake in New Zealanders was estimated by the ESR for the Health Department in a 2009 report.
This report identifies many groups who can exceed the limit for chronic daily ingestion set by the ATSDR of 0.05 mg/kg of body weight/day. These include young infants and children, Maori, Pacific Islander and deprived groups, diabetics, athletes, kidney patients, and outdoor workers