Concurrent 2,4-D and triclopyr biomonitoring of backpack applicators, mixer/loader and field supervisor in forestry

Abstract

Two herbicides, 2,4-D and triclopyr esters (application ratio 1.6:1 acid equivalents) were applied as a tank mix by a crew of 8 backpack sprayer applicators, a mixer/loader, and a field supervisor. The crew was employed in a conifer release program in northern California during the summer of 2002. Biomonitoring (urine, 24 h) utilized 2,4-D and triclopyr (a.e.) as rapidly excreted exposure biomarkers. The absorbed dosages of 2,4-D and triclopyr were calculated based upon cotton whole body suits and biomonitoring. Dosages based upon accumulation of the herbicides on body suits averaged 42.6 μg (a.e.) 2,4-D/kg-d and 8.0 μg (a.e.) triclopyr/kg-d. Six consecutive days of concurrent urine collections showed that backpack applicators excreted an average of 11.0 μg (a.e.) 2,4-D/kg-d and 18.9 μg (a.e.) triclopyr/kg-d. Estimates based upon curve fitting were 17.1 and 29.3 μg (a.e.)/kg-d, respectively. Results suggest that passive dosimetry for 2,4-D consistently overestimated the dosage measured using biomonitoring by a factor of 2-3 fold, while for triclopyr, passive dosimetry underestimated the absorbed dose based on biomonitoring by a factor of 2-4 fold.

Keywords:

• Exposure assessment
• forestry
• triclopyr
• 2,4-D
• biomonitoring
• backpack

Acknowledgments

The USDA Forest Service and the Division of Agricultural and Natural Resources, University of California supported this work. Tom Young of Fruit Growers Supply Company, Hilt, CA provided invaluable assistance. Alfonso Gallegos and other workers of Great Tree Tenders were welcome partners in this research. The continuing interest and support of John Taylor of the US Forest Service is gratefully acknowledged. Mike Wright of McKenzie/Wright Laboratories contributed valuable expertise and analytical support. Helen Vega is thanked for general assistance and manuscript preparation.