GENTECH archive


Bt toxic also for human ?

It seems that Bt could be toxic (at least in a bacteria) also
to humans.

Yet it has been said for a long while (and it is currently repeated by biotechs)
that Bt is safe to humans !


>Thursday, June 17, 1999
>The dried spores of the bacteria Bacillus thuringiensis, known as Bt, one
>of the few insecticides sanctioned for use on organic crops in Europe, may
>be harmful to the human immune system, according to a report in the May 29
>issue of New Scientist.
>French scientists at le Bouchet army research laboratories near Paris found
>that the spores caused lung inflammation, internal bleeding and death in
>laboratory mice.
>The dried spores of Bt have been used as a pesticide for more than 30 years
>and also widely used to combat pests such as the spruce budworm, a
>caterpillar that attacks trees.
>Last year, French scientists isolated a strain of Bt that destroyed tissue
>in the wounds of a French soldier in Bosnia. The strain, known as H34, also
>infected wounds in immuno-suppressed mice. Now the same team has found that
>H34 can kill mice with intact immune systems if they inhale the spores.
>Francoise Ramisse of le Bouchet and her colleagues found that healthy mice
>inhaling 108 spores of Bt H34 died within eight hours from internal
>bleeding and tissue damage. Spores from mutants of the same strain which
>did not produce the insecticide were equally lethal to mice, suggesting
>that it was not to blame.
>The researchers think that the symptoms are caused by other toxins. The
>bacterium's close cousin, Bacillus cereus, produces a toxin that ruptures
>cell membranes. And in 1991, Japanese researchers showed that B.
>thuringiensis produces the same toxin.
>Ramisse said that companies producing Bt spores might make them safer by
>deleting the promoter sequence that activates the gene for the
>membrane-rupturing toxin.
>Although H34 is not used as a pesticide, commercial strains of Bt tested by
>the researchers also killed some mice or caused lung inflammation when
>The team obtained these strains from Abbott Laboratories, a supplier of
>Bt-based pesticides in Chicago, Ill. Ramisse said that the strains are
>sprayed on forest pests at concentrations of 1011 spores per square meter
>and thus might pose a danger to people in the immediate vicinity.
>Linda Gretton, a spokeswoman for Abbot, told New Scientist that their
>products were safe and that the company stands by its products.
>Copyright 1999, Environmental News Network