Urinary 2,4-D concentrations measured in studies of general population groups (CDC, 2005; Morgan et al. 2008) are summarized in Table 2. Exposure pathways for persons in the general population may include ingestion of residues in food products, inhalation, and direct contact with dust (Morgan et al. 2004, 2008). The measured urinary concentrations are presented in the context of the appropriate BE values based on the U.S. EPA chronic RfD in Figure 1. The urinary levels of 2,4-D observed in the general population samples are far below the BE value corresponding to the U.S. EPA chronic RfD, with median and upper bound measured concentrations more than 100- and 50-fold below the BERfD.
Corresponding data for farmers and members of their families obtained in the days immediately following application of 2,4-D (Alexander et al. 2007; Arbuckle and Ritter 2005; Arbuckle et al. 2002, 2004; Curwin et al. 2005; Thomas et al. 2009) are summarized in Table 3. Exposure pathways for non-applicators on the farm may include secondary exposure to field, farm machinery, or the applicator, and drift of herbicide during application with resulting inhalation, dermal and oral exposure following contact with residues on surfaces in the home. Urinary concentrations collected from farm family members in the day or days immediately following application of 2,4-D fell below the applicable acute BE values.
Measured urinary concentrations in farmers involved in application of 2,4-D are presented in the context of BE values corresponding to the U.S. EPA occupational exposure guidance values in Figure 2. Again, the data suggest an overall margin of safety, with median or geometric mean levels in farmers involved in application of 2,4-D more than 25-fold below the occupational BE target value. However, some individuals had single spot urinary concentrations that approached the occupational BE target value. The highest urinary level of 2,4-D reported in Thomas et al. (2009) on Day 5 following application was 2500 μg/L, in excess of the occupational BE value of 2000 μg/L (data Page 13 of 31 not shown). However, all other reported occupational measurements were below the occupational BE.