A paper in the current issue by Yousefi et al. examined data on the prevalence of fertility, infertility, and abortion (miscarriage), in the health records of 3,392 women, aged 10–49 yr, living in two regions of Poldasht county, Iran, with low and high drinking water fluoride ion (F) levels (means 1.90 and 8.10 mg/L, respectively) and found that those in the low F group (n=1,294), when compared to those in the high F group (n=2,098), were more fertile (p<0.05) and had lower rates of (i) infertility without known etiological f actors (p<0.001) and (ii) abortion without known etiological factors (p<0.001). A safe daily dose of F to prevent the adverse effects of infertility and abortion in humans of approximately 0.6 mg F/day was calculated from the findings of Yousefi et al. by taking conservative figures so as not to produce a falsely low safe dose [estimated daily F in take from drinking 1.5 L of water with 8 mg F/L = 12 mg F, estimated daily F intake from food = 5 mg, estimated total daily intake = 17 mg F, uncertainty factor to convert from a Lowest Observed Adverse Effect Level (LOAEL) to a No Observed Adverse Effect Level (NOAEL) = 3, uncertainty factor to allow for inter-individual variability = 10, total uncertainty factors = 30, 17 ÷ 30 = 0.56, approximately 0.6 mg F/day or, assuming a body weight (bw) of 56 kg, 0.01 mg F/kg bw/day]. In conclusion, while a maternal dose of 0.6 mg F/day or 0.01 mg F/kg bw/day can be estimated to be protective of impaired fertility and abortion in humans, this level of intake is above the estimated maternal dose of 0.04 mg F/day, or 0.0007 mg F/kg bw/day, necessary to protect the foetus from neurotoxicity.