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What is the quantity of Cry1Ab toxin in one corn plant? Does it exist in the corn pollen? It would appear there are problems for measuring the quantity of Cry1Ab toxin produced according to Food and Agricultural Immunology - FOOD AGRIC IMMUNOL 01/2012; 23(2):99-121. DOI:10.1080/09540105.2011.604773 Are there any benefits the regarding breakdown of toxin before consumption when topically sprayed vs being preserved in the plant tissue? "Bt toxins sprayed on plants break down quickly when exposed to UV light. Bt toxins produced in the plant are protected from UV light." http://www.ext.colostate.edu/pubs/crops/00707.html Is it possible it may be for this reason why it was found in the blood of pregnant women? http://www.ncbi.nlm.nih.gov/pubmed/21338670 When pesticide measurements are considered, are the plant producing quantities counted as overall pesticide use on US crops?
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A:Expert Answer

Q1: What is quantity of Cry1Ab toxin in one corn plant? 

 

The short answer is, it depends on what specific corn variety or plant part is tested and the environment the plant was grown in, but in all cases, the levels of Cry1Ab are considered low enough to have a very low probability of causing any health risk upon ingestion by people or animals or to negatively impact other organisms, such as beneficial insects.

 

The longer answer is that there are 47 different maize events (independent versions) producing Cry1Ab that have been sold commercially since 1996, by at least three different companies (Syngenta, Dow AgroSciences, Monsanto). These events have been marketed in hundreds of varieties. The amount of Cry1Ab produced in these many varieties will differ, in some cases because the company intentionally designed the new gene to be active in only certain parts of the plant, primarily leaves and stalk where the Lepidopteran insects (those with a caterpillar larval stage) would be expected to feed and do damage.

 

The amount of Cry1Ab will also vary some due to the environmental conditions in which the plant is grown. Despite all the potential for variability, the documents that are submitted by the companies to gain regulatory approval by the USDA, FDA and EPA provide estimates of the amount of Cry1Ab in different plant parts grown in field trials, and it is usually produced at very low levels. The detailed information can be found at the database on approved GMO crops through the link at the GMO Answers website. A direct link to the relevant information on Cry1Ab is provided here: http://www.isaaa.org/gmapprovaldatabase/gene/default.asp?GeneID=26&Gene=cry1Ab.

 

The test that the questioner refers to in the publication is one way to measure Cry1Ab quantity; it is designed to be a rapid test for presence or absence, but it is not the most precise method that could be used. The major point of the publication is that different labs do use this test and get results in a similar range, but if standardized procedures were used, they could be more accurate. While more accurate testing procedures would have no impact on the safety of a corn variety engineered to express the Cry1Ab protein (as indicated above, the levels present are not considered to present a health risk to humans or other organisms) they could be important when marketing corn to U.S. trade partners. The reason this matters is that in some markets, like the EU, maize with less than 1 percent GM doesn’t need to labeled as GM, and so it can be a big deal if the test variability is the difference between whether a shipment of grain can be considered GM-free (more valuable) and whether it is GM (less valuable). 

 

Q2: Are there any benefits the regarding breakdown of toxin before consumption when topically sprayed vs being preserved in the plant tissue? "Bt toxins sprayed on plants break down quickly when exposed to UV light. Bt toxins produced in the plant are protected from UV light."http://www.ext.colostate.edu/pubs/crops/00707.html

 

A2: It is true that Bt toxins produced in the plant would be protected from UV light, whereas Bt in sprays would be exposed to UV light. However, this does not mean that the Bt protein in the plant is more stable than that in sprays, because plant cells also produce enzymes that recycle proteins and lead to breakdown of Bt protein.

 

Q3: Is it possible it may be for this reason why it was found in the blood of pregnant women?http://www.ncbi.nlm.nih.gov/pubmed/21338670 

 

The published article that the questioner mentions reported that Cry1Ab protein could be detected in blood samples from non-pregnant women, pregnant women and fetal cord blood. The study unfortunately used the same low-sensitivity method mentioned above for Q1, which will provide inaccurate results when used with blood samples, and was not even conducted properly by the scientists who published the article. There are other good methods for detecting Cry1Ab in blood samples, but the authors of the study did not use them to confirm their results. Because the science was not at a high standard in this article, many scientists will question the validity of the results, and in fact a number of them wrote letters to the editor or commented on the article as such.

 

Q4: When pesticide measurements are considered, are the plant producing quantities counted as overall pesticide use on US crops?

 

Yes, the EPA considers any type of Bt protein a “biopesticide” and, as it does with chemical insecticides, estimates total environmental levels of exposure over short and long time scales. Because a number of studies have demonstrated that Bt proteins produced in crop plants degrade quickly in nature (within a year or less), there is little concern of environmental accumulation over time. The amounts of Bt protein produced by all crops combined in the U.S. on an annual basis is much lower than the amount of chemical sprays used, to the point that it doesn’t contribute much to the total pesticide use.

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