Glyphosate undergoes microbial degradation in soil, sediment and natural waters, under both aerobic and anaerobic conditions. The major metabolite formed is aminomethylphosphonic acid (AMPA), which binds tightly to most soils and is degraded by microbial processes over time. Glyphosate and AMPA are ultimately degraded to carbon dioxide, inorganic phosphate, and other naturally occurring compounds.
The U.S. EPA determined in 1993 that AMPA is not of toxicological concern.
The Joint FAO/WHO Meetings on Pesticide Residues (JMPR) reviewed the available AMPA studies in 1997 and compared the toxicity profile of AMPA with that of glyphosate and concluded that the toxicity of AMPA had been thoroughly investigated and that the studies demonstrate little potential for harm. The Meeting concluded that glyphosate and AMPA have similar toxicological profiles and, because AMPA was considered to be of no greater toxicological concern than glyphosate, a full database on AMPA is unnecessary. This conclusion was reaffirmed by JMPR in 2004.
The World Health Organization has also reviewed water quality data for glyphosate and AMPA and concluded because of their low toxicity, under usual conditions, the presence of glyphosate and AMPA in drinking water does not represent a hazard to human health.