Bti [short for Bacillus thuringiensis subspecies israelensis] is a biological, naturally occurring, bacterium found in soils. According the US EPA, "... microbial pesticides have undergone extensive testing prior to
registration. They are essentially nontoxic to humans, so there are no concerns for human
health effects with Bti or B. sphaericus when they are used according to label directions."
According to and Canadian PMRA
Mammals do not have an apparatus that can activate the toxin contained in Bti, and therefore it is safe for humans.
In its 2006 re-evaluation of the
registration of Bacillus thuringiensis, the Pest Management Regulatory Agency (PMRA) states that:
"...
Consumption of treated products cannot be expected to pose a risk to the public,
children and infants. The risk of exposure through
drinking water is negligible. The low toxicity of Bacillus thuringi ensis and the demonstration of its
safety suggest that human exposure through drinking
water does not pose a significant risk.”