SAfETY of Bt Crops to Humans and Other Vertebrates

As in the case of Bt insecticides, tests of Bt crop safety to humans are not done directly. Instead, as is done with many other products, the safety of Bt crops to humans is assessed by inference rather than by experiments that use humans as test animals in replicated studies. Specifically, the safety of these crops to humans is based on a variety of evidence from other sources, including previous safety studies of Bt insecticides along with experiments against other vertebrate animals (Table 3.8). With no evidence indicating a risk to ingesting Bt insecticides containing Cry proteins (for example, as has been used on organic crops for decades), and no adverse effects from feeding Cry proteins to vertebrate hosts (be they from Bt or produced in surrogate hosts), the first Bt crops were released commercially in the United States in 1996. Since then, products derived from Bt cotton and Bt corn, including cotton seed oil and various syrups and stabilizers, have been used in hundreds of food products consumed by humans. Thus, millions of Americans have been eating Bt crop products on a routine basis for more than 10 years.

In addition, corn grain and cottonseed has been used for many years as animal feed for beef and milk cattle, and chickens, which we eat in substantial quantities. Cynically, one could argue that Americans are the experimental animals used to test the safety of Bt crops to humans. But it must be realized that tons of bacterial insecticides based on Bt, as noted above, have been used on organic crops for decades, with no confirmed negative effects on human health (see Section 3.3.2 above). It would have been irresponsible for governmental officials such as those in the EPA to not include this information in their "weight of evidence" and risk assessment analyses of Bt crops based on Cry proteins. We have now exceeded 10 years of consumption of Bt crop products by hundreds of millions of people in the United States, with no

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-Isogenic Control -■- Pyrethroid-treated -H- Stacked Bt

- Corylophidae

- Araneae

" Anthocoridae ~ Formicidae

- Thripidae Coccinellidae

- Diptera

- Phalacridae

* Predatory Mites

* Chrysomelidae

Aphididae

Agromyiidae

Cantharidae

Chrysopidae - Nitidulidae

FIGURE 3.6 Principal response curves for arthropod aerial communities exposed to Cry1Ab + VIP3A corn versus pyrethroid-treated corn. Trials were conducted in the state of Maryland during 2000-2002. Community densities in conventional nontreated corn are represented by the straight line at 0.0. Arthropod population fluctuations for Bt corn are represented by the line with white squares, and pyrethroid populations by the lines with black squares. Differences in the types of arthropod population fluctuations are shown to the left. Arrows indicate timing of pyrethroid applications. See Dively, G. P., Impact of transgenic VIP3A x Cry1Ab lepidopteran-resistant field corn on the nontarget arthropod community, Environ. Entomol., 34, 1267, 2005 for details.

epidemiological evidence of any negative effects on human health. If fact, it is easy to argue that Bt crops represent a truly "green" technology, as the extensive plantings of these crops have led to reductions of millions of pounds of synthetic chemical insecticides per year, while at the same time preserving natural enemy populations. Some may say that hindsight is better than foresight, but the available science on the specificity of Cry proteins, and tests done either on Bt crops or surrogate proteins used in place of these crops, justified the decision to release these crops for animal and human consumption. Now, after more than 10 years of consumption by humans, these decisions have been vindicated.

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