Biomonitoring data for 2,4-dichlorophenoxyacetic acid in the United States and Canada: interpretation in a public health risk assessment context using Biomonitoring Equivalents.
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.
Aylward
Lesa L
LL
Summit Toxicology, LLP, Falls Church, Virginia 22044, USA. laylward@summittoxicology.com
Morgan
Marsha K
MK
Arbuckle
Tye E
TE
Barr
Dana B
DB
Burns
Carol J
CJ
Alexander
Bruce H
BH
Hays
Sean M
SM
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
D015084:2,4-Dichlorophenoxyacetic Acid