Lar wrote:
....

The toxicity of chemicals are compared to each other by a measurement
called an LD50...the lower the number the more toxic the product. The
LD50 of boric acid for rats is around 2660, relatively safe to be
around.

My exposure to "LD50" considerations was when the US Military was trying
to get volunteers to take anthrax vaccination shots. They wanted to
impress people with just how deadly anthrax is. "LD50" is the Leathal
Dose (in grams????) which will kill 50% of the population. [I seem to
remember a gram of anthrax will kill sheep a mile away!]