Male infertility is responsible for about 50% of the fertility problems that couples face. Infertility in males is often the result of reduced sperm court, abnormal sperm quality (e.g., reduced motility and altered morphology), or altered levels of sex hormones (e.g., reduced testosterone). A review of over 100 studies of sperm density from 1938 to 1996  found that human sperm count has significantly declined in North America and Europe since the 1940s. (Swan 2000) While the causes of this decline are not entirely known, fluoride exposure — particularly from high-concentration topical fluoride gels — must be considered as one of the potential contributing factors.

Fluoride Affects Sperm Quality at Concentrations Found in Human Blood Following Use of Topical Fluoride Gels

In 2002 and again in 2006, researchers from Poland reported that exposing ram semen to 0.38 parts per million (20 umol/L) of fluoride for 5 hours was sufficient to “cause a statistically significant decrease in the motility of spermatoza and the number of intact acrosomes.” (Zakrzewska 2002). As the authors noted, these changes would “undoubtedly affect the physiological function of the sperm.” Prior to the Polish team’s findings, researchers from Texas found that infusing testis with higher, but still relatively modest, levels of fluoride (4.75 ppm) “unequivocally” inhibited the synthesis of testosterone. (Chubb 1985). Read More.

The Polish team’s findings are of particular importance when considering that from the 1960s to the 1990s, the use of high-concentration topical fluoride gels produced blood concentrations in boys and men that far exceeded 0.38 ppm. In tests on both children and adults, the use of topical fluoride gels at the dental office has been found to produce blood fluoride concentrations as high as 1.2 ppm, or four times higher than the concentration found to damage sperm. (Ekstrand 1980, 1981). Further, the blood fluoride concentrations have been found to exceede 0.38 ppm for up to six hours after treatment (longer than the length of time that the Polish researchers exposed the semen). Although most dentists now use precautionary procedures (e.g., suction devices) to reduce blood fluoride concentrations following application of fluoride gels, available data shows that children will still routinely ingest enough fluoride from topical gels to reach blood fluoride concentrations exceeding 0.38 ppm.

Fluoride Exposure Damages Male Reproductive System in Animals

Consistent with the in vitro research, over 60 animal studies have found that fluoride adversely impacts the male reproductive system. The effects — which have been observed in rats, mice, chickens, and rabbits — include: (1) decreases in testosterone levels; (2) reduced sperm motility; (3) altered sperm morphology; (4) reduced sperm quantity; (5) increased oxidative stress; (6) and reduced capacity to breed. While the studies have generally used high doses, many of the studies have found effects at dosages that would produce blood fluoride concentrations far lower than the concentrations used in the in vitro research. See, e.g., Sun (2010); Dvoráková-Hortová (2008); Sharma (2008); Reddy (2007); Gupta (2007); Pushpalatha (2005). In one of the few studies to report blood fluoride concentrations, Mexican researchers reported that blood fluoride levels of 0.2 to 0.26 ppm for an eight week period caused increased oxidative stress, reductions in sperm motility and reduced fertility in male rats.  Izquierdo-Vega, et al. (2008).

While some studies have not found any effects of high fluoride dosages on the reproductive functions of male rats , these studies represent the distinct minority in the field. (Sprando & Collins 1996, 1997, and 1998). One possible explanation for the discrepancy in findings is the nutritional health of the tested animals. As with many other areas of fluoride research, nutritional deficiencies (e.g., protein) unequivocally exacerbate fluoride’s reproductive effects, whereas  nutritional supplementation (e.g., protein or anti-oxidants such as vitamin C) can significantly prevent or ameliorate these effects.

High Fluoride Exposure Linked to Reduced Testosterone and Decreased Fertility in Humans

Consistent with the in vitro and animal research, studies of human populations have reported associations between fluoride exposure and damage to the male reproductive system. Most notably, a scientist at the Food & Drug Administration reported in 1994 that populations in the United States with more than 3 ppm fluoride in their water had lower “total fertility rates” than populations with lower fluoride levels. (Freni 1994). While 3 ppm is a higher concentration than used in water fluoridation programs (0.7 to 1.2 ppm), it is still considered a “safe” level by the EPA. To date, no U.S. health agency has attempted to replicate Freni’s findings. However, three studies of highly fluoride-exposed populations in China and India have found that high fluoride exposure is associated with reduced male fertlity. (Chen 1997; Liu 1988; Neelam 1987). In addition, five studies from China, India, Mexico, and Russia.have found that high-fluoride exposure is associated with reduced male testosterone levels. (Hao 2010; Ortiz 2003; Susheela 1996; Michael 1996; Tokar 1977).

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