Preliminary studies on the bioavailability and disposition of bioincurred carrot residues of [14C] linuron and [14C]3,4-dichloroaniline in rats.

Carrots grown from seed in soils spiked with [14C = O]linuron or [14C-ring]3,4-dichloroaniline (DCA), were found to contain radioactivity equivalent to 0.73 ppm linuron or 0.60 ppm DCA. After exhaustive extraction with methanol these tubers still retained 35% and 67% of the original 14C-bioincurred residues, for linuron and DCA respectively. To examine the bioavailability of these residues, rats were dosed by gavage (water vehicle) with unextracted tubers and extracted tubers. For comparison purposes 14C-spiked carrot tubers and [14C] standards were also administered. Animals were maintained for 3 days in metabolism cages; urine, faeces, expired gases and several tissues were collected for radioassay. The following relative amounts of radioactivity (expressed as a percentage of the applied dose) were excreted (faeces/urine) for linuron or DCA dosing respectively: unextracted carrots, 28/31, 51/10; extracted carrots, 51/0, 73/3; spiked carrots, 11/43, 63/20; and linuron and DCA standards, 11/46, 26/81. The data demonstrated that approximately 31% and 10% of bioincurred 14C-residues (from linuron and DCA respectively) in unextracted carrot tubers were bioavailable to rats. 14C-Bound residues (extracted tubers) were much less bioavailable (0% and 3% respectively). The disposition of radioactivity in tissues, blood and expired gases was very low (less than or equal to 1.3% per sample) for any dose studied.