Measuring human exposure to genetically modified organisms is extremely difficult for two reasons. The first is the pervasiveness of GMO products in the U.S. marketplace. GMOs are present in approximately 70% of processed foods and have been consumed widely in the U.S. since 1996 (GEO-PIE, 2002). Once a GMO is approved for human consumption in the U.S., no effort is made to keep approved GM crops from mixing with their traditional counterparts during their production, distribution and processing (Taylor, 2003). This is due to the U.S. governments judgment that once a GMO passes pre-market safety testing, it is considered to be as safe its traditional counterpart and no post-market regulation is necessary. In the absence of food labeling and traceability programs it is impossible to know exactly who is being exposed to genetically modified foods and the intensity of the exposures (Taylor, 2003).
The second factor that makes measuring exposure a major challenge is the lack of reliable physiological tests to detect the presence of GMOs in the human body post-consumption. Currently there are no methods to detect novel DNA from an inserted gene in the human body primarily because DNA is quickly digested in the GI track (Cockburn, 2002). Methods do exist for detecting potential allergic reactions to GM foods. The FDA has developed a serological test to detect an antibody to the Cry9c protein that could serve as evidence of an allergic reaction to Starlink corn (CDC, 2001).
In 2000, the FDA and CDC carried out an investigation of reports of human illnesses that were potentially linked to Starlink Corn consumption (CDC, 2001). The CDC conducted an epidemiological study by administering questionnaires to individuals who had reported a food illness, had manifested symptoms consistent with a food allergy, and had consumed products that contained corn. They also obtained relevant medical records and collected serum samples for further analysis. The FDA used the serological test mentioned above to test the serum samples for evidence of an allergic reaction to Starlink corn. The test did not produce any evidence of an allergic reaction to either Starlink corn or any other food for that matter. The agencies could not confirm an adverse reaction to Starlink corn. They would not rule out the possibility, however, because of significant limitations in their ability to confirm exposure to the GM corn. The experience of the two agencies illustrates the difficulty of measuring human exposure to GMOs.
Cockburn, A. (2002). Assuring the safety of genetically modified (GM) foods: The importance of an holistic, integrative approach. Journal of Biotechnology, 98, 79-106.
Cornell Universitys Genetically Engineered Organisms Public Issues Education Project (GEO-PIE). August 8, 2003.
Investigation of human health effects associated with potential exposure to genetically modified corn. A report to the FDA from the CDC, June 11, 2002.
Taylor, M., and Tick, J. Post-market oversight of biotech foods. The Pew Initiative on Food and Biotechnology. April, 2003.