France 24 reports that “France has asked its national health body to verify a study released this week linking Monsanto’s NK603 genetically modified corn to cancer in rats, saying the results of the probe could lead to an ’emergency suspension’ of NK603 imports.” NK603 is modified to be resistant to Monsanto’s popular herbicide Roundup (glyphosate), thus allowing farmers to use the product as a post-emergencce herbicide without damaging feral crops.
The results of this study are inherently controversial. Regulators have set relatively high tolerances for it because few biological effects have previously been observed even at very high doses. For example, EPA’s Reference Dose (RfD) for glyphosate is 0.1 mg/kg/day, a factor of 10 below the highest No Observed Exposure Level (NOEL). The NOEL applies to biological effects that are generally agreed to be non-adverse, not cancer.
EPA also has set a primary drinking water standard, called a Maximum Contaminant Level ([MCL), of 700 parts per billion (ppb). This level is precautionary; according to EPA, “Some people who drink water containing glyphosate in excess of the MCL over many years could experience problems with their kidneys or reproductive difficulties.” The multiple qualifications in this statement (some people, over many years, could experience) hint at the extent of this precaution.
How could a chemical that has been shown to be relatively benign cause cancer?