Percutaneous absorption and excretion of alachlor in rhesus monkeys

Quantitative analysis of alachlor protein adducts by gas chromatography-mass spectrometry

This study examined the potential use of hemoglobin (Hb)- and serum-protein adducts of alachlor as potential biomarkers of alachlor exposure, a genotoxic and carcinogenic herbicide. The method developed was based on the observation that cleavage of S-cysteinyl alachlor-protein adducts by methanesulfonic acid gave the rearrangement product 3-(2',6'-diethylphenyl)-1, 3-thiazolidine-4-one (TZO). The structure of TZO was confirmed by mass spectroscopy, NMR spectroscopy, and independent synthesis. In the assay, treatment of alachlor-cysteinyl protein adducts by methanesulfonic acid was followed by extraction and analysis. TZO was detected and quantitated by electron-impact GC/MS in the single ion-monitoring mode. [ring-13C6]Alachlor-N-acetylcysteine was added as an internal standard prior to treatment and was converted to [ring-13C6]TZO, allowing response factors to be used to quantitate TZO concentrations. Incubations of alachlor (0-1000 microM) with human albumin and bovine serum albumin (BSA) resulted in linear adduct formation with both proteins. Maximal adduction levels of 613-1130 pmol alachlor-albumin adducts/mg protein were observed, with BSA binding close to twice that of human albumin. A linear concentration response of alachlor-Hb adducts was observed when whole blood from female CD rats was incubated with alachlor in vitro at concentrations up to 300 microM. Maximal binding was 1860 pmol alachlor-Hb adducts/mg globin. Male CD rats treated with alachlor at 150 mg/kg body wt/day ip for 0, 1, 2, and 3 days were sacrificed 4 days after final dosing. A maximal binding of 2250 pmol alachlor-Hb adducts/mg globin was observed. This assay provides a new approach for biomonitoring alachlor levels in experimental animals and has the potential for use in humans.

In vivo percutaneous absorption and skin decontamination of alachlor in rhesus monkey

The objectives of this study were to determine the percutaneous absorption of alachlor relative to formulation dilution with water, and to determine the ability of soap and water, and of water only, to remove alachlor from skin, relative to time. Alachlor is a preemergence herbicide. The in vivo percutaneous absorption of alachlor in rhesus monkeys was 17.3 +/- 3.3, 15.3 +/- 3.9, and 21.4 +/- 14.2% for 24-h skin exposure to Lasso formulation diluted 1:20, 1:40, and 1:80, respectively. In vivo, there was no support for increased alachlor skin absorption with water dilution, as previously reported for in vitro absorption. The average in vivo absorption of 18% applied dose over 24 h (0.75%/h) was similar to the maximum in vitro rate of 0.8%/h using human skin and human plasma as receptor fluid. Dose accountability in vivo was 80.6-95.2%. [14C]Alachlor in Lasso diluted 1:20 with water was placed on rhesus monkeys at concentrations of 23 micrograms/10 microliters/cm2. Skin decontamination at 0 h with soap and water (50% Ivory liquid 1:1 v/v with water) removed 73 +/- 15.8% (n = 4) of the applied dose with the first wash; this increased to a total of 82.3 +/- 14.8% with two additional washes. Decontamination after 1 h removed 87.5 +/- 12.4% with three successive washes. After 3 h decontamination ability decreased, and after 24 h only 51.9 +/- 12.2% could be recovered with three successive washes. Using water only, at 0 h 36.6 +/- 12.3% alachlor was removed with the first wash and the total increased to 56.0 +/- 14.0% with two additional washes. At 24 h the total amount decreased to 28.7 +/- 12.2% for three successive washes. Alachlor as Lasso in field-use rate (11 micrograms/cm2) and undiluted (217 and 300 micrograms/cm2) proportions were left on rhesus monkey skin for 12 h and decontaminated with soap and water (10% Ivory liquid v/v with water). Continual successive washes (6-8 in sequence) recovered 80-90% of the skin-applied alachlor. These results suggest that simple washing with soap and water is appropriate for removing some chemicals from skin. Decontamination with only water was less effective than with soap and water.

The effect of Lasso herbicide on human immune function as measured by in vitro assays

Using in vitro assays, this study was undertaken to determine whether the components of Lasso herbicide formulation had an effect on the human immune system. Mononuclear cells from human peripheral blood were exposed to analytical alachlor, alachlor conjugated to human serum albumin or Lasso formulation over a concentration range from .01 microM-1.0 microM. The effects of the test materials on the following immunological functions were determined: lymphocyte proliferation induced by mitogen or antigen; antibody synthesis of IgG and IgM isotypes in pokeweed stimulated mononuclear cell cultures; cytotoxic T cell proliferation; lysis of target cells by natural killer cells and lymphokine activated killer cells. The data demonstrated that the test compounds had no significant, dose related effect on the function of immunocompetent cells. Hence, the data suggest that the components of the Lasso formulation have no effect on the human immune system.

In vitro percutaneous absorption and stratum corneum binding of alachlor: effect of formulation dilution with water

The effect of vehicle dilution on the percutaneous absorption of alachlor, 2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide, through excised human skin was determined using flowthrough design glass penetration cells and 14C radiotracer methodology. Three dilutions of alachlor (in the solubilizing commercial formulation) with distilled water were utilized: 1:20, 1:40, and 1:80 (v/v); corresponding to concentrations of 23.0, 11.8, and 5.98 mg alachlor per milliliter, respectively. Skin from the penetration studies and human powdered stratum corneum from the binding studies demonstrated a high capacity for alachlor. A soap and water (1:1, v/v) solution effectively decontaminated powdered stratum corneum. Using plasma as the receptor solution, penetration ranged from 0.5 to 4% of the applied dose for an 8-hr exposure period. Lag times of 1.2 to 1.8 hr were observed. Increasing dilution resulted in significant enhancement (p less than 0.01) in the rate and extent of alachlor penetration. Although the biological significance of this observation is unclear, this phenomenon might be explored in future studies because of its ramifications for human toxicity and for decontamination opportunities.