Effects of soil on percutaneous absorption of toluene in male rats

Abstract

Previous assessments of health risks from soil-adsorbed chemical exposures relied on extrapolations from data derived with pure compounds. However, interactions between chemical and soil can alter the rate, amount, and form of chemical that enters the body, resulting in effects that are different from those that occur after exposures to chemical alone. In this study, male rats were treated dermally with [14C]toluene alone or adsorbed to either a sandy or a clay soil. Both soils produced a higher plasma concentration compared to pure toluene, with a statistical decrease in half-life of absorption observed after sandy soil-adsorbed treatment. The time to reach peak plasma concentration, half-life of elimination, and area under the plasma concentration-time curve (AUC) were similar for all groups. Skin and fat contained the highest concentration of radioactivity 48 h after all treatments. Pure and soil-adsorbed toluene were primarily metabolized and excreted via the kidney rather than exhaled. Furthermore, soil treatment did not alter the percentages of the metabolic products.

Dermal absorption of environmental contaminants from soil and sediment: a critical review

“…Use of soils with unrealistic particle size ranges is commonly reported. Clearly, Wester et al (1990Wester et al ( , 1992aWester et al ( , b 1993aWester et al ( , b, c, 1995Wester et al ( , 1996 and Poet et al (2000aPoet et al ( , b, 2002 removed the fine fraction of their soils, and it appears the Skowronski and colleagues did as well (Skowronski et al, , 1989(Skowronski et al, , 1990(Skowronski et al, , 2000Abdel-Rahman et al, 1989, 2002Turkall et al, 1994;Kadry et al, 1995).…”

“…Riviere, 2000; a portion of the results reported in Roy et al, 1998). Skowronski et al (1988Skowronski et al ( , 1989Skowronski et al ( , 1990) used concentrations of benzene, toluene, and m-xylene more than 100 times higher than estimated soil saturation limits (see Table 2). Poet et al (2000bPoet et al ( , 2002 used maximum concentrations of PCE and TCE approximately 4-80 times estimated soil saturation limits.…”

“…Notably, the experiments of Wester et al (1990Wester et al ( , 1992bWester et al ( , 1993aWester et al ( , b, c, 1996 and Mayes et al (2002) using rhesus monkeys in vivo involved protocols that would have allowed substantial sloughing of soil. In many of the other published in vivo studies description of methods is insufficient to permit assessment of continuity of contact (Poiger and Schlatter 1980;Shu et al, 1988;AbdelRahman et al, 1992;Skowronski et al, 1988Skowronski et al, , 1989Skowronski et al, , 1990Yang et al, 1989;Roy et al, 1990a, b;USEPA 1991;Turkall et al, 1994;Kadry et al, 1995;Qiao et al, 1997). An exception is the in vivo human hand immersion protocol used by Poet et al, (2000aPoet et al, ( , b, 2002.…”

“…Another prolific research group did more fully describe their methods, but in many cases did not allow any time for contaminant-soil equilibration, first applying soil to skin and then applying the contaminant to soil (Skowronski et al, , 1989(Skowronski et al, , 1990Abdel-Rahman et al, 1989Turkall et al, 1994;Kadry et al, 1995;non-aged soils in Skowronski et al, 2000and Abdel-Rahman et al, 1997, 2002.…”

“…At 48 h the rats were killed, and their livers were digested and analyzed by liquid scintillation counting. Skowronski et al (1988Skowronski et al ( , 1989Skowronski et al ( , 1990; Abdel- ; Abdel-Rahman et al (1992) In Vivo: Rat Three very similar in vivo studies were conducted using male Sprague-Dawley rats with the solvents benzene, toluene, and m-xylene. Two soils described as having organic carbon contents of 4.4% and 1.6% and particle sizes in the 50-500 mm range were employed.…”