Re: boron toxicity
Here is an pdf with pretty much all you need to know about boron.
"Type of animal Type of effect Daily intake of boron
Rat No effect is seen. This is the NOAEL for the Rat. 9.6 mg/kg body weight per day
Rat The weight of fetuses is slightly reduced, and rib anamolies may be present. 13 mg/kg maternal body weight per day
Rat Changes in the testicles which lead to sterility 55 mg/kg body weight per day
Rabbit Malformations of the heart and the circulatory system 25 mg/kg maternal body weight per day
Mouse Fetal body weight can be affected 80 mg/kg maternal body weight per day"
http://www.greenfacts.org/en/boron/boron-greenfacts-level2.pdf
Consider you take 500 mg of borax daily; which is approx 55 mg. of boron.
For my weight (60 kilos)that would be 0.916 mg of boron per kilo. Far away from the NOAEL on 9.6 mg per kilo.
I have taken borax for 3,5 years, still alive and doing well!