Drastic Measures: Understanding Chemical Exposures in the Modern World
The pesticide glyphosate is the most heavily used agricultural chemical in the world, with over 800 thousand tons used annually. Glyphosate exposure has been linked to a variety of negative health effects in humans, including cancer and preterm birth, but the scientific evidence showing these links is new and controversial. Glyphosate is applied to a variety of crops, and can still be measured in those crops by the time they reach grocery stores. This means that every time we sit down for a meal, we are at risk of being exposed. For farmworkers and those living in agricultural communities, the risk of glyphosate exposure may be even higher than in the general population. To determine the health effects of glyphosate exposure, we must first be able to accurately measure how much glyphosate an individual has been exposed to. Researchers commonly attempt to characterize glyphosate exposure by measuring glyphosate concentrations in a single urine sample. Since glyphosate levels in the body fluctuate, single urine samples represent only very recent experiences and are likely to misclassify long-term exposure. This misclassification has the potential to endanger public health by systemically underestimating the strength of the relationship between glyphosate exposure and potential health effects. The primary goal of this thesis is to determine the minimum number of urine samples that are required to accurately characterize long-term glyphosate exposure, which is vital to inform future glyphosate research and protect public health.