Percutaneous penetration of 2,4‐dichlorophenoxyacetlc acid and 2,4‐d dimethylamine salt in human volunteers

Abstract

The percutaneous penetration of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-D dimethylamine salt (DMA) was evaluated separately in five male volunteers who participated in both experiments. Urine samples collected for 144 h following dermal applications of 10 mg to the dorsum of the hand (9 cm2) were analyzed for 2,4-D. Following the acid application, an average of 4.46 +/- 0.849% was recovered in the urine and a significantly lower amount of 1.76 +/- 0.568% following the DMA application. Significantly higher amounts of 2,4-D DMA (7.68 +/- 0.493 mg) were washed off the hand 6 h following application as compared with 2,4-D acid (5.35 +/- 0.384 mg). These results indicate that, in addition to the differences in physical and chemical properties of the two compounds that will affect absorption, the amount of the chemical absorbed is related inversely to the amount of washed off. Urinary excretion of 2,4-D was not complete in all volunteers 144 h following either application, but in all cases it was approaching the limit of detection. An average of 84.8 +/- 2.55% and 76.8 +/- 8.05% of the total recovered in 144 h was recovered in the urine 96 h following 2,4-D acid and 2,4-D DMA application, respectively. Average, approximated half-lives for excretion were 39.5 +/- 8.1 h for the acid application and 58.5 +/- 13.2 h for the DMA application.

Indirect sources of herbicide exposure for families on Ontario farms

“…To do this, we converted our study exposure values, represented as 2,4-D in urine in applicators, spouse and child, to a unit exposure value for the total 48 h urine collection period that was utilized in the present study. An important limitation of this approach was the fact that our 48 h urinary collection period likely did not reflect the total dose, although other studies that collected urine to assess exposure to 2,4-D have indicated that a 48 h collection period would certainly have been adequate to have captured the majority of the absorbed dose (Feldman and Maibach, 1974;Harris and Solomon, 1992). Utilizing this approach, we determined that the average body burdens were 0.89 mg/kg body weight for applicators, 0.016 mg/kg body weight for spouses and 0.10 mg/kg body weight for children, assuming default body weights of 77, 62 and 39 kg for applicators, spouses and children, respectively.…”

Development of models to predict dose of pesticides in professional turf applicators

“…Following an oral, dermal or inhalation exposure to 2,4-D ( dimethylamine salt ), close to 100% of the absorbed dose is excreted in the urine as 2,4-D acid over a 5 -to 6 -day period (Feldman and Maibach, 1974;Kohli et al, 1974;Sauerhoff et al, 1977;Harris and Solomon, 1992b). Following repeated exposures, a steady state for 2,4-D body burden would be reached following approximately four half -lives or 4-5 days of consecutive exposure, if the exposure to 2,4-D, on a daily basis, remains relatively constant.…”

“…Due to its low vapour pressure and volatility, the major route of exposure to 2,4 -D amine salts is dermal, and air sampling studies have shown that respiratory exposure is minimal ( Libich et al, 1984;Grover et al, 1986;Harris and Solomon, 1992b). Therefore, the self -administered questionnaire was designed primarily to evaluate factors that could directly or indirectly affect dermal pesticide exposure.…”

Toxicology of Specific Substances

“…Usually these substances are the metal salts, alkylamine salts or esters, although the most toxic form is the acid metabolite (Harris and Solomon 1992). The best known herbicides of this group are 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), mecoprop and fenoprop.…”