Agreement of pesticide biomarkers between morning void and 24-h urine samples from farmers and their children

Abstract

In pesticide biomonitoring studies, researchers typically collect either single voids or daily (24-h) urine samples. Collection of 24-h urine samples is considered the "gold-standard", but this method places a high burden on study volunteers, requires greater resources, and may result in misclassification of exposure or underestimation of dose due to noncompliance with urine collection protocols. To evaluate the potential measurement error introduced by single void samples, we present an analysis of exposure and dose for two commonly used pesticides based on single morning void (MV) and 24-h urine collections in farmers and farm children. The agreement between the MV concentration and its corresponding 24-h concentration was analyzed using simple graphical and statistical techniques and risk assessment methodology. A consistent bias towards overprediction of pesticide concentration was found among the MVs, likely in large part due to the pharmacokinetic time course of the analytes in urine. These results suggest that the use of single voids can either over- or under-estimate daily exposure if recent pesticide applications have occurred. This held true for both farmers as well as farm children, who were not directly exposed to the applications. As a result, single void samples influenced the number of children exposed to chlorpyrifos whose daily dose estimates were above levels of toxicologic significance. In populations where fluctuations in pesticide exposure are expected (e.g., farm families), the pharmacokinetics of the pesticide and the timing of exposure events and urine collection must be understood when relying on single voids as a surrogate for longer time-frames of exposure.

Variability of urinary concentrations of polycyclic aromatic hydrocarbon metabolite in general population and comparison of spot, first-morning, and 24-h void sampling

“…However, this sampling method is burdensome on the study subjects, and non-compliance can lead to compromised or a biased sampling. A common alternative is to collect the first-morning urine, as has been done in many occupational and environmental exposure investigations, because the first-morning urine is often correlated with the 24-hour void (Han et al 2008;Scher et al 2007;Kissel et al 2005). In epidemiological studies such as NHANES involving thousands of participants, first-morning voids are often difficult to obtain; hence, spot urine samples have been used as a more practical solution.…”

Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment

“…Although 24-h urine sampling is certainly a preferred method for such analyses, it is seldom done for logistical reasons. To evaluate the potential magnitude of errors in using spot urine samples to estimate daily excretion rates, Scher et al (2007) compared the TCPy concentration in 24-h urine collections to "spot" urine samples (first morning void) in farmers and farm children potentially exposed to chlorpyrifos. They concluded that "A consistent bias towards overprediction of pesticide concentration was found among the MVs [morning voids], likely in large part due to the pharmacokinetic time course of the analytes in urine," and noted that this was true for both farmers and their children.…”

Population variability of phthalate metabolites and bisphenol A concentrations in spot urine samples versus 24- or 48-h collections

“…In the third study, Scher et al 18 collected first morning voids and 24-h samples from farmers and their children potentially exposed to chlorpyrifos. They measured 3,5,6-trichloro-2-pyridinol (TCP), a chlorpyrifos metabolite, in the first morning void the day following application of chlorpyrifos to a nearby agricultural field, and in the corresponding 24-h void for the day following application.…”