title: Biomonitoring data for 2,4-dichlorophenoxyacetic acid in the United States and Canada: interpretation in a public health risk assessment context using Biomonitoring Equivalents.
abstract: BACKGROUND
  Several extensive studies of exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) using urinary concentrations in samples from the general population, farm applicators, and farm family members are now available. Reference doses (RfDs) exist for 2,4-D, and Biomonitoring Equivalents (BEs; concentrations in urine or plasma that are consistent with those RfDs) for 2,4-D have recently been derived and published.
  
  
  OBJECTIVE
  We reviewed the available biomonitoring data for 2,4-D from the United States and Canada and compared them with BE values to draw conclusions regarding the margin of safety for 2,4-D exposures within each population group.
  
  
  METHODS
  Data on urinary 2,4-D excretion in general and target populations from recent published studies are tabulated and the derivation of BE values for 2,4-D summarized.
  
  
  RESULTS
  The biomonitoring data indicate margins of safety (ratio of BE value to biomarker concentration) of approximately 200 at the central tendency and 50 at the extremes in the general population. Median exposures for applicators and their family members during periods of use appear to be well within acute exposure guidance values.
  
  
  CONCLUSIONS
  Biomonitoring data from these studies indicate that current exposures to 2,4-D are below applicable exposure guidance values. This review demonstrates the value of biomonitoring data in assessing population exposures in the context of existing risk assessments using the BE approach. Risk managers can use this approach to integrate the available biomonitoring data into an overall assessment of current risk management practices for 2,4-D.
authors.affiliation: Summit Toxicology, LLP, Falls Church, Virginia 22044, USA. laylward@summittoxicology.com
authors.forename: Lesa L
authors.initials: LL
authors.lastname: Aylward
authors.forename: Marsha K
authors.initials: MK
authors.lastname: Morgan
authors.forename: Tye E
authors.initials: TE
authors.lastname: Arbuckle
authors.forename: Dana B
authors.initials: DB
authors.lastname: Barr
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Burns
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Alexander
authors.forename: Sean M
authors.initials: SM
authors.lastname: Hays
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000009:adverse effects / Q000032:analysis* / Q000652:urine; D002170:Canada; D004781:Environmental Exposure / Q000032:analysis*; D006801:Humans; D011634:Public Health / Q000379:methods*; D018570:Risk Assessment / Q000379:methods*; D014481:United States
chemical_list: D015084:2,4-Dichlorophenoxyacetic Acid