Bayer CropScience's position on the findings of glufosinate and its metabolite.

A recently published paper in Reproductive Toxicology by uthors Aris and Leblanc reported the potential for maternal and etal exposure to certain pesticides associated with genetically odified foods (PAGMF) [1]. The authors conclude among other hings that both maternal and fetal exposure to the glufosinate etabolite 3-methylphosphinicopropionic acid (3-MPPA) results rom the approved agricultural uses of glufosinate in Canada, as evienced by detectable levels of 3-MPPA in serum samples obtained rom pregnant women and their fetuses. The authors also suggest hat given the biological and toxicological effects of this metaboite, which they state are similar to those of the parent compound, ore studies are needed to better understand the potential impact f 3-MPPA on the fetus. Glufosinate residues were also reported, ut only in plasma of non-pregnant women. Bayer CropScience (BCS), as the primary registrant of the active ngredient glufosinate-ammonium, has several issues with the ublication. We find a number of incorrect statements in the paper n addition to possible analytical inadequacies and implausibilities hich we believe should be clarified. To begin, BCS would like to point out that the metabolite 3PPA is not a significant residue in glufosinate-tolerant crops; the −) isomer of N-acetylglufosinate (NAG) is the major metabolite n glufosinate-tolerant crops (1998 JMPR residue review) [2]. Of ote, there is a complete regulatory toxicology dossier available or NAG which includes rat and rabbit teratology studies; there is o evidence of teratogenicity in either species (1999 JMPR toxicity eview, and EU DAR) [3,4]. 3-MPPA is a major residue in conventional crops, and a signifcant body of guideline toxicity studies is available for 3-MPPA hich have been recently reviewed in the EU re-registration rocess according to Directive 91/414/EEC. BCS challenges the ssertion that 3-MPPA has similar biological and toxicological ffects to glufosinate based on this existing significant body of data hich apparently was not known by the authors. 3-MPPA does ot inhibit glutamine synthetase and therefore by definition canot have similar biological properties (Koecher and Dickerhof) [5] nd (ENV/JM/MONO(2002)14) [6]. In the 2002 EU Draft Assessment eport (DAR), the Rapporteur Member State concluded that there ere no teratogenic effects in either the rat or rabbit teratology tudies for 3-MPPA. The 2005 EFSA Scientific Report [7] stated that oxicity studies carried out on NAG and 3-MPPA indicate that these etabolites are of lower toxicity than glufosinate. More importantly, BCS has reason to doubt the accuracy of the eported serum levels for 3-MPPA. Aris and Leblanc analyzed their amples according to the method described by Motojyuku et al. 8] who reported that a peak derived from endogenous plasma omponents interfered with analysis of 3-MPPA. Although Aris and eblanc reported 3-MPPA in every sample of maternal and fetal cord lood and most samples of non-pregnant women, insufficient detail [