Does NHANES underestimate true population-based exposures to pesticides? Exploring bias in NHANES human biomonitoring data.

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SUMMARY/ABSTRACT Human biomonitoring (HBM) – the measurement of a chemical, its reaction product, or metabolite in biosamples – is an exposure assessment technique that is often considered the “gold standard” in exposure assessment. The US uses the National Health and Nutrition Examination Survey (NHANES) as a vehicle for sample collection for its national HBM program. NHANES data collection occurs in Mobile Examination Centers (MEC), large trailers containing a mobile laboratory. Scheduling site locations for data collection includes considerations such as seasonal weather patterns and difficulties with MEC unit transit. Because MEC units cannot easily traverse difficult roadways with snow and ice patching, logistics require that sampling in areas often hit with harsh winter weather occur during the warmer months (i.e., spring and summer) whereas more temperate locations can be sampled in cooler months (i.e., winter and autumn). Given this, NHANES data that may vary by season could be subject to both temporal and spatial bias. This potential bias could, in turn, lead to inaccurate interpretations of population exposure and health data. We will evaluate any bias in HBM data of seasonal chemicals from NHANES using two specific aims. 1) Conduct state-level and seasonal evaluations of distributions of seasonal and non-seasonal chemical urinary biomarkers in NHANES Cycles 1999-2016 using the NCHS Research Data Center allowing access to restricted geocodes and sampling dates. 2) Compare NHANES state-level urinary pesticide metabolite data to smaller-scale biomonitoring studies conducted in different US states during different seasons. This study could provide information that will enable CDC to reconsider their sampling logistics to better represent seasonal and regional variations or will enable us to quantify the extent to which NHANES underestimates US population exposures.