The NHANES 2015–2016 aromatic diamine urinary biomonitoring data: A critical review and suggestions for improved data collection

The 2015–2016 National Health and Nutrition Examination Survey (NHANES) included biomonitoring of aromatic diamines obtained after acid hydrolysis of urine samples for the first time. Aromatic diamines in hydrolyzed urine are biomarkers that are not unique to a single substance. Without further information, that renders association with potential exposures very difficult. This review provides an overview of potential sources of urinary aromatic diamines, the most important being aromatic diisocyanates (occupational and home-use), aromatic diamines themselves (predominantly from hair dye products), and polyurethanes (medical devices and implants). Expected urinary diamine concentrations from these and other sources as well as background levels are evaluated based on available literature data. Finally, recommendations are made to improve the value of future data collections. These include analytical enhancements, better mapping of potential sources of the biomarkers prior to conducting the survey, and documentation of product use to enable identification of exposure sources. These improvements are indispensable for investigating potential links with medical conditions should this be envisioned.