3.4—Whole Bt-producing bacteria are safe (that's why organic growers use it!)


The Bt in crops is no more toxic than the Bt in bacteria.

See Genetic Roulette’s False Claims at Bottom of Page

Analysis of Peer-Reviewed Research:

Genetic Roulette claims that because Bt in crops doesn’t wash off, because it is modified to be active upon ingestion, and because there is much more of it, we should believe that the Bt in crops is more toxic.  Yes, it is more toxic to insects—that’s why Bt crops work so well.  There is no data presented by Smith in this section that shows that Bt in crops is more toxic to humans or animals.  Studies have repeatedly shown that animals can consume large amounts of Bt without ill effect–in fact, Bt protein is digested just like any other. This is called nutrition.  Once again Smith makes a scary claim for which he can advance no factual evidence or logical argument.

1.  Bt-toxins that are sprayed on plants don’t persist, while Bt proteins that are produced in plants do persist, which is one of the reasons Bt crops are more effective than Bt sprays. Scientists incorporate Bt into plants so that the plants produce biopesticide continually.  Not surprisingly, they often target Bt production to the leaves, stems or roots depending on the insect pest that is being defended against (Ely and others 2000, Russell and Fromm 1997, Song and others 2000). This lowers costs since less insecticide is used, along with less labor and fuel (Brookes and Barfoot 2007).  Research shows that Bt crops also have far less environmental impact than spraying chemical pesticides (and probably less than spraying Bt biopesticides)

2.  The Bt-toxins incorporated into plants are modified so that they will act quickly and they are present at high levels in order to delay development of resistance. Scientists are able to produce plants that more effectively control pests than Bt sprays. Bt sprays are not always effective and it is difficult to achieve high concentrations of Bt on crops plants (Nester and others 2002).  Because of this, resistance to Bt has emerged in the Diamond Back moth (Shelton and others 1993).  Developers of Bt crops found a way to make Bt more potent as well as to increase the levels of Bt in the plant tissues in order to retard the development of resistant insects. They also modified the molecule so that it didn’t need to be partially digested by the insect to be active.

3. The Bt used in Bt crops is safe for humans and animals so increases in exposure to humans and animals are of no consequence. Smith’s claims that the modified Bt molecules used in groups could cause more antibodies to be formed are meaningless since IgE antibodies associated with Bt allergy have never been reported (Siegel 2001, Betz and others 2000).  Despite years of planting hundreds of millions of acres of Bt crops, allergies or other adverse effects in humans have not occurred.  Similarly, increases in Bt potency and concentration are not important because not only have adverse effects not been observed during widespread use, there are scientific studies that tell Bt proteins are not allergens or toxins in animals (Siegel 2001, Betz and others 2000).  Bt proteins are very specifically toxic to a few closely related insects (Nester and others 2002; Whalon and Wingerd 2003).  Developers of Bt crops, and other researchers, have published studies which show that animals can be fed Bt at doses that are thousands to millions of times higher than a human or animal would encounter in a Bt crop without any toxic effect.  Put another way, these studies show that we can safely eat grams of Bt proteins while Bt crops contain only micrograms.  That’s why regulators are able to approve Bt crops.  Bt proteins don’t hurt mammals.  We have to add here that the life-cycle of the bacteria that produce these Bt proteins is one of natures’ wonders.  They are insect pathogens that produce proteins that kill only their host insects but which do not affect other insects.  This phenomenon is called biological specificity.

4.  Smith’s arguments in section 3.4 offer no evidence of harm. Smith argues that exposure is higher and that the molecules are different but he provides no evidence that this causes harm.  He is essentially arguing more is worse and different is worse.   Many of the claims in Genetic Roulette follow this pattern.  The only actual claim of adverse effect is to Green Lacewings that have consumed lepidoptera that has consumed Bt corn containing at Bt called Cry1Ab— a study that was shown to be in error in 2004 (Romeis and others 2004)—long before Smith wrote Genetic Roulette.  There are two important points to note here: 1) for scientific findings to be accepted they must be independently validated—in this case the claim was shown by other scientists to be incorrect, and 2) Smith either doesn’t know the scientific literature or is intentionally hiding information from the reader that doesn’t support his views.

References

Betz FS, Hammond BG, and Fuchs, RL (2000). Safety and advantages of Bacillus thuringiensis-protected plants to control insect pests. Regulatory Toxicology and Pharmacology 32:156-177.

Brookes G and Barfoot P (2007). Global impact of biotech crops: Socio-economic and environmental effects, 1996-2006. AgBioForum, 11: 21-38. Available on the World Wide Web: www.agbioforum.org.

Ely S, Evans IJ and Schuch WW (2000). Root specific promoter. World Patent WO/2000/029594 International Application No.PCT/IB1998/002000

Nester EW and others (2002).100 Years of Bacillus thuringiensis: A Critical Scientific Assessment.  A report from the American Academy of Microbiology.  2002.http://academy.asm.org/images/stories/documents/100yearsofbtcolor.pdf

Romeis J, Dutton A, and Bigler F (2004). Bacillus thuringiensis toxin (Cry1Ab) has no direct effect on larvae of the green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae). Journal of Insect Physiology 50:175–183.

Russell DA and Fromm ME (1997). Tissue-specific expression in transgenic maize of four endosperm promoters from maize and rice. Transgenic Research 6, 157–168 (1997)

Shelton AM, Robertson JL, Tang JD, Perez C, Eigenbrode SD, Preisler HK, Wilsey WT, and Cooley RJ (1993). Resistance of diamondback moth to Bacillus thuringiensis subspecies in the field. J. Econ. Entomol. 86: 697-705.

Siegel JP (2001). The mammalian safety of Bacillus thuringiensis- based insecticides. Journal of Invertebrate Pathology.  77:13-21

Song P, Heinen JL, Burns TH, and Allen RD (2000). Expression of two tissue-specific promoters in transgenic cotton plants. The Journal of Cotton Science 4:217-223

Whalon ME and Wingerd BA (2003). Bt: Mode of action and use Archives of Insect Biochemistry and Physiology, 54: 200-211.

Genetic Roulette Falsely Claims:
The Bt in crops is more toxic than the Bt spray
1. The Bt-toxin in GM crops is more harmful than Bt spray due to differences in the concentration and form of protein.

2. Bt sprays are used intermittently and degrade in the environment.

3. The Bt-toxin in crops is thousands of times more concentrated and is continuously produced in every plant cell.

4. The form of the Bt-toxin protein in GM crops is also more toxic.

Smith claims that the Bt-toxin in GM crops is more toxic than the Bt-toxin in bacterial sprays.

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