Pilot study evaluating inhalation and dermal glyphosate exposure resulting from simulated heavy residential consumer application of Roundup^®

Abstract

Objectives

The purpose of this study was to evaluate the individual contributions of inhalation and dermal exposures to urinary glyphosate levels following the heavy residential consumer application of a glyphosate-containing herbicide.

Methods

A pilot study was conducted in which each participant mixed and continuously spray-applied 16.3 gallons of a 0.96% glyphosate-containing solution for 100 min using a backpack sprayer. Twelve participants were divided evenly into two exposure groups, one equipped to assess dermal exposure and the other, inhalation exposure. Personal air samples (n = 12) and dermal patch samples (n = 24) were collected on the inhalation group participants and analyzed for glyphosate using HPLC-UV. Serial urine samples collected 30-min prior to application and 3-, 6-, 12-, 24-hr (inhalation and dermal groups) and 36-hr (dermal group only) post-application were analyzed for glyphosate and glyphosate’s primary metabolite (AMPA) using HPLC-MS/MS.

Results

The mean airborne glyphosate concentration was 0.0047 mg/m³, and the mean concentrations of glyphosate for each applicator’s four patch samples ranged from 0.04 µg/mm² to 0.25 µg/mm². In general, urinary glyphosate, AMPA, and total effective glyphosate levels were higher in the dermal exposure group than the inhalation exposure group, peaked within 6-hr following application, and were statistically indistinguishable from background at 24-hr post-application.

Conclusions

This is the first study to characterize the absorption and biological fate of glyphosate in residential consumer applicators following heavy application. The results of this pilot study are consistent with previous studies that have shown that glyphosate is rapidly eliminated from the body, typically within 24 hr following application.

Keywords:

• Glyphosate
• Roundup
• toxicokinetics
• exposure

Disclosure statement

At the time this study was conducted, all of the authors were employed by a consulting firm that provides scientific advice to the government, corporations, law firms and various scientific/professional organizations. This firm has been engaged by companies involved in litigation, however, none of the authors have served as testifying experts in glyphosate litigation. The time invested by the authors to write this paper was provided by their employer, and no client or defendant in litigation requested that this work be performed. No external funding was received for the research supporting the analysis, nor the time needed to prepare the article. Furthermore, the work product including the conclusions drawn are exclusively those of the authors.