Glyphosate and aminomethylphosphonic acid in human hair quantified by an LC‐MS/MS method

Abstract

An LC-MS/MS method for hair testing of glyphosate and aminomethylphosphonic acid (AMPA), its main biodegradation product, has been developed. After decontamination, 50 mg of hair was ground and sonicated in water for 2 h. The method was fully validated in the 5-500 pg/mg range for glyphosate and 10-500 pg/mg for AMPA, and the limits of detection were 2 and 5 pg/mg, respectively. Matrix effect for glyphosate and AMPA was compensated by an isotope-labeled internal standard.Hair samples from four farmers who regularly used glyphosate and one farmer who used glyphosate but not his wife and 14 hair samples from nonoccupationally exposed subjects were tested. Glyphosate was found in head hair of three farmers, with concentration in the range 14-188 pg/mg. The fourth was found negative but with hair colored in red. Glyphosate was detected in 10 of 14 hair samples from nonoccupationally exposed subjects at concentrations of 11.5 pg/mg or lower and only in one segment (0-3 cm) of the farmer's spouse (6 pg/mg). AMPA was detected in five subjects, above the limit of quantification only in two of three occupationally exposed subjects with positive glyphosate.Further studies should be conducted to validate this potential new biomarker that could be useful for assessing long-term exposure to glyphosate.aminomethylphosphonic acid, biomonitoring, glyphosate, hair, long-term exposure | INTRODUCTIONGlyphosate (N-phosphonomethyl-glycine, M w = 169.1, Figure 1a) was registered in 1974 in the United States as a broad-spectrum contact herbicide. Its use has dramatically increased by more than 100-fold over the past four decades, and global estimates of its use suggest that sufficient glyphosate-based herbicide was applied in 2014 to spray nearly 0.5 kg of glyphosate on every hectare of cropland on the planet, making glyphosate the most widely used herbicide in the world (Vandenberg et al., 2017). Once applied, it diffuses into water where it persists for many weeks before being transformed by bacteria into aminomethylphosphonic acid (AMPA, Figure 1b) (La Cecilia & Maggi, 2018). Its environmental half-life is 47 days at 25 C with light exposure or 267 days in the dark at the same temperature (Mercurio et al., 2014). This persistence increases the risk, as with many pesticides, of accumulation and environmental exposure to this compound.In 2015, the European Food Safety Authority defined an acute reference dose (ARfD), corresponding to an estimate of a substance that can be ingested once without appreciable health risk to the consumer.Glyphosate ARfD has been estimated at 0.5 mg/kg of body weight, thus recognizing for the first time an acute toxicity of this chemical (European Food Safety Authority, 2015). Few epidemiological studies examining the impact of chronic glyphosate exposure on human diseases have been published. On March 20, 2015, the International Agency for Research on Cancer of the World Health Organization classified glyphosate in group 2A of active chemicals, namely a probable carcinogen to humans (Guyton et al., 2015). ...