Urinary concentrations and determinants of glyphosate and glufosinate in pregnant Canadian participants in the MIREC study.

Ashley-Martin J, Huang R, MacPherson SH, Brion O, Owen J, Gaudreau E, Bienvenu JF, Fisher M, Borghese, MM, Bouchard MF, Lanphear BP, Foster WG, Arbuckle TE. Environmental Research 2022 Nov 18;217:114842. doi: 10.1016/j.envres.2022.114842

Glyphosate is a chemical ingredient in herbicides, such as Roundup®, that is widely used in agricultural settings to control weeds. Glufosinate is another herbicide ingredient that has become more popular in recent years due to the increasing number of weeds that are resistant to glyphosate. There is limited data available on the levels of herbicides that women are exposed to during pregnancy.

The MIREC study recruited about 2000 pregnant women from 10 Canadian cities between 2008 and 2011. During clinic visits, women provided urine samples and completed a questionnaire on their usual diet and whether they used pesticides. Using very sensitve laboratory methods, concentrations of glyphosate and glufosinate as well as their metabolites (break down products) were measured in urine samples collected during the first trimester of pregnancy. Using statistical models, researchers described the concentrations of herbicides in urine samples and determined whether there were statistical patterns between diet, pesticide use and chemical concentrations.

Nearly three quarters of women had low – but detectable – concentrations of glyphosate in their urine. Very few women had detectable levels of glufosinate. Nearly three quarters of women also had detectable levels of glyphosate’s break down product – AMPA (aminomethylphosphonic acid).

Women who ate whole grain bread more frequently during pregnancy tended to have higher concentrations of glyphosate in their urine. Although few women used pesticides during pregnancy, those women who did use pesticides did not have higher urinary concentrations of glyphosate than women who never used them.

These results suggest that pregnant women are widely exposed to low levels of glyphosate and that diet may be a source of exposure. It is important to keep in mind that the levels of glyphosate measured in the urine were quite low and below what Health Canada considers to be a level of concern to human health.

This research was led by scientists at Health Canada.

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