Biomonitoring data for 2,4-dichlorophenoxyacetic acid (2,4-D) in urine samples are now available from a number of studies of both the general population (including preschool aged children) and farm applicators and their family members (Alexander et al. 2007; Arbuckle and Ritter 2005; Arbuckle et al. 2002, 2004, 2006; CDC 2005; Morgan et al. 2008).
Such data provide an integrated measure of absorbed dose from all pathways and routes of exposure.
The hazards of 2,4-D were recently assessed by the United States Environmental Protection Agency (U.S. EPA 2004) and the Canadian Pest Management Regulatory Agency (PMRA 2007).
The U.S. EPA-derived reference doses (RfDs) for acute and chronic exposure to 2,4-D are based on external exposure metrics (administered dose), which are not directly useful for evaluating biomonitoring data.
However, Biomonitoring Equivalent (BE) values corresponding to RfDs for acute and chronic exposure scenarios are now available (Aylward and Hays 2008) and can be used as a tool for assessing the biomonitoring data directly in a public health risk assessment context, without requiring calculation of corresponding external dose, as has previously been done (Mage et al. 2004).
This paper reviews urinary biomonitoring data for 2,4-D from several studies in the general population and in farmers and farm family members and evaluates the data in the context of the BE values for 2,4-D presented in Aylward and Hays (2008) to assess the current margin of safety (ratio of exposure guidance value such as an RfD to exposure measures) for population exposures to 2,4-D in the United States and Canada.