Heather Bedard, C.H.E.
I couldn’t find any well-designed studies that showed that fluoride causes cancer. Many of the studies that I found used mice/rat profiles and these are not always applicable to human expression. Other studies were small and only showed possible associations to osteosarcoma, a type of bone cancer.[1]
However, an excess of fluoride can cause fluorosis (toxic levels of fluoride) at levels as low as 1.5mg/l while the average amount of fluoride added to public drinking water in many areas is 1mg/l. The damaging effects of fluoride on the body include oxidative stress, an increased risk of diabetes, and obesity.[2] All of these issues come with an increased risk of various cancers. Diabetes can increase your risk from a 20% and obesity from 9.5%.[3],[4] Due to this, and the other damaging effects of high fluoride intake, care should be taken with the amount of fluoride that one ingests to mitigate their risk of cancer.
-------------------- [1] Bassin EB, Wypij D, Davis RB, Mittleman MA. Age-specific fluoride exposure in drinking water and osteosarcoma (United States). Cancer Causes Control. 2006;17(4):421-428. doi:10.1007/s10552-005-0500-6 [2] Kurdi MS. Chronic fluorosis: The disease and its anaesthetic implications. Indian J Anaesth. 2016;60(3):157-162. doi:10.4103/0019-5049.177867 [3] Larsson SC, Mantzoros CS, Wolk A. Diabetes mellitus and risk of breast cancer: a meta-analysis. Int J Cancer. 2007;121(4):856-862. doi:10.1002/ijc.22717 [4] https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet#r32