Exposure estimation to glyphosate through the consumption of wheat flour in Lebanon

Abstract

Background and objective: The world average yield of wheat, rice, and maize has doubled 20 folds since 1964 due to the increase in pesticide use. Glyphosate, a broad spectrum herbicide, is globally used in crop production and is residual in soil and water. Several research findings on glyphosate residues in different food groups and human exposure remain controversial as to whether or not it increases the risk of cancer and other health implications. In Lebanon, there is no current data to estimate glyphosate concentration and exposure in different food groups. This study quantified glyphosate in imported wheat flour and local flour available in markets located in Mount Lebanon (n=84) and assessed the exposure of the population to glyphosate through wheat flour consumption. Methods: Enzyme linked immunosorbent assay (ELISA) method was applied to quantify glyphosate residues in 100% of imported flour from Beirut port and local flour available on the Lebanese market in Mount Lebanon (n=84) including all purpose, pastry, whole wheat, Lebanese bread flour and others (cake flour, semolina, durum wheat, pizza flour, and type 00 for pasta). Glyphosate levels were compared to maximum residue levels (MRLs) of 5 mg/kg, 10 mg/kg, and 30 mg/kg for wheat as indicated by Australia, Europe, and United States respectively. Glyphosate concentrations of imported wheat flour were compared to 20 mg/kg for wheat bran, unprocessed as indicated by the Lebanese ministry of agriculture in line with codex alimentarius. Exposure assessment of Lebanese population to glyphosate through flour consumption was also estimated and compared to ADI (1 mg/kg/day) and ADI 0.3 mg/kg/day. Findings: All types of flour available on the Lebanese market including all purpose, pastry, whole wheat, Lebanese bread, and others were 100% positive for glyphosate. The glyphosate median residue levels were highest in other flours (102.9 ppb) as compared to the Lebanese bread flour (57.8 ppb), all purpose (50.3 ppb), pastry (45.2 ppb) and whole wheat flour (43.5 ppb). The difference in glyphosate concentration among different flour types was not significant (p=0.75). All tested samples prevailed glyphosate concentrations below the MRLs. The Estimated Daily Intake (EDI) of glyphosate through flour consumption in Lebanon was estimated at 0.1318 μg/kg BW/day which is only 0.00022% of the Acceptable Daily Intake (ADI) of 1 mg/kg/day as indicated by the US Environmental Protection Agency and European Food Safety Authority, and 0.00073% of the ADI of 0.3 mg/kg/day as indicated by the Australian Pesticides and Veterinary Medicines Authority. Conclusion: Different types of flour available on the Lebanese market contained glyphosate residues with no significant difference between various categories, local, and main imported flour. All tested samples were compliant with MRLs and exposure assessment indicated a low risk of the population through the consumption of wheat flour. Future extensive studies need to evaluate the exposure of the population to glyphosate from other staple foods and through different routes of exposure due to bio accumulation of glyphosate.