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Comment & Response
April 3, 2018

Glyphosate Levels in Older Adults—Reply

Author Affiliations
  • 1Family Medicine and Public Health, University of California, San Diego, La Jolla
  • 2Radiology, University of California, San Diego, La Jolla
JAMA. 2018;319(13):1385. doi:10.1001/jama.2018.0216

In Reply We are keenly aware that the topic of glyphosate is highly controversial, often acrimonious, and stretches across diverse political and geographical boundaries.

Dr Karberg and colleagues had concerns about our assay. We were not able to include details of our assay methods as we were limited to 6 references. The methodology we used was developed by a research team led by Monsanto scientists.1 Validation of urine levels included accuracy, precision, specificity, linearity, LOQ (glyphosate and aminomethylphosphonic acid [AMPA] LOQs were set conservatively at 0.25 μg/L), and LOD (glyphosate LOD = 0.03 μg/L; AMPA LOD = 0.04 μg/L). We used accepted and published methods assigning samples as 0 that had values below the LOD. This, together with our conservative LOQ, biased our findings toward underestimating the actual amount of glyphosate in the urine samples.