glifosato (erbicida) presente nei geni degli OGM

[realGpigeon]

Un interessante studio ha individuato nei geni di soia e mais geneticamente modificato la presenza di metaboliti del glifosato, noto erbicida, per la fattispecie N-acetato di glifosato, N-acetato AMPA e AMPA. Le dosi letali dalla assunzione di questi metaboliti è di 200 grammi in uomo adulto.

GLYPHOSATE (158) AND METABOLITES
TOXICOLOGY Glyphosate (N-(phosphonomethyl)glycine) is a non-selective systemic herbicide that was last evaluated by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) in 2004, when a group acceptable daily intake (ADI) for glyphosate and aminomethylphosphonic acid (AMPA), the main metabolite of glyphosate, of 0–1 mg/kg body weight (bw) was established based on a no-observed-adverse-effect level (NOAEL) of 100 mg/kg bw per day for salivary gland alterations in a long-term study of toxicity and carcinogenicity in rats and a safety factor of 100.
The 2004 JMPR concluded that it was not necessary to establish an acute reference dose (ARfD) for glyphosate.
Metabolism studies in genetically modified soya beans and maize containing the glyphosate-N-acetyltransferase (GAT) gene demonstrated that new metabolites are formed that were not observed in conventional crops. The major metabolite in the new maize and soya bean varieties was N-acetyl-glyphosate, whereas glyphosate, N-acetyl-AMPA and AMPA were found in low concentrations in the edible parts of the crops. The present Meeting was asked by the Codex Committee on Pesticide
Residues to evaluate newly submitted studies on toxicokinetics and metabolism, acute oral toxicity, subchronic toxicity and genotoxicity for N-acetyl-glyphosate and on acute oral toxicity and genotoxicity for N-acetyl-AMPA.
All pivotal studies were certified as complying with good laboratory practice or an approved quality assurance programme.
Biochemical aspects [14C]
N-acetyl-glyphosate was rapidly and incompletely (approximately 66%) absorbed in rats following a single oral dose of 15 mg/kg bw. The maximum concentration of radioactivity in plasma was reached after 2 hours, and the half-life for elimination from plasma was 15.6 hours. Elimination was mainly via urine (66.1%) and, to a lesser extent, faeces (26.4%); more than 90% of the total radioactivity was eliminated by 48 hours post-dosing.
N-Acetyl-glyphosate was metabolized to a very limited extent. One metabolite, glyphosate (< 1% of the total radioactivity), was detected in faeces after a single oral dose of 15 mg/kg bw, whereas glyphosate and N-acetyl-AMPA were found in urine
following subchronic exposure at dose levels of 56 mg/kg bw per day and above.
Toxicological data
N-Acetyl-glyphosate, was of low acute oral toxicity; the median lethal dose (LD50) was greater than 5000 mg/kg bw in rats.
In a 90-day study of toxicity with N-acetyl-glyphosate in rats, the NOAEL was 4500 ppm (equal to 283 mg/kg bw per day), based on slightly decreased body weight gains in male rats at 18 000 ppm (equal to 1157mg/kg bw per day) N
-Acetyl-glyphosate was tested for genotoxicity in vitro and in vivo in an adequate range of assays; it was not found to be genotoxic in mammalian and microbial test systems.
The Meeting concluded that N-acetyl-glyphosate was unlikely to be genotoxic.
The Meeting concluded that N-acetyl-glyphosate is of no greater toxicological concern than the parent glyphos rate, based on the structural similarity of N-acetyl-glyphosate with glyphosate and supported by the following considerations: 1)
N-acetylation is a common detoxification pathway of xenobiotic compounds in mammals; therefore, N-acetyl-glyphosate is expected to be of similar Glyphosate 146 toxicity to or lower toxicity than glyphosate;
2)
a structure –activity relationships analysis indicates that the N-acetylated group is not a structural alert for carcinogenicity, mutagenicity or endocrine effects; and
3)
the toxicological data for N-acetyl-glyphosate show low acute toxicity, low subchronic toxicity (with no organ toxicity in rats at doses up to 1157 mg/kg bw per day) and a lack of genotoxicity.
N-Acetyl-AMPA
N-Acetyl-AMPA was of low acute oral toxicity; the LD50 was greater than 5000 mg/kg bw in rats.
N-Acetyl-AMPA was tested for genotoxicity in vitro and in vivo in an adequate range of assays; it was not found to be genotoxic in mammalian or microbial test systems.
The Meeting concluded that N-acetyl-AMPA was unlikely to be genotoxic.