Bioconcentration factor of relatively low concentrations of chlorophenols in Japanese medaka

Bioconcentration factors (BCF) for pentachlorophenol (PCP) and 2,4-dichlorophenol (2,4-DCP) in Japanese medaka (Oryzias latipes) were determined at five different concentrations of the chemicals, between 0.1 and 10 μg/l (PCP), 0.3 and 30 μg/l (2,4-DCP), in the ambient water. Medaka were exposed to each chemicals in a continuous-flow system during the embryonic development period and 60 days after hatching from eggs collected in the laboratory. Both the exposure time and the aqueous concentrations are much more realistic and closer to natural aquatic environments than those used in conventional BCF studies. The BCF values of PCP were from (4.9 ± 2.8) × 103 at the aqueous concentration of 0.074 ± 0.028 μg/l to (2.1 ± 1.4) × 103 at 9.70 ± 0.56 μg/l. The BCF value of 2,4-DCP were from (3.4 ± 3.0) × 102 at 0.235 ± 0.060 μg/l to 92 ± 27 at 27.3 ± 1.6 μg/l. Generally, BCF values increased as the aqueous concentrations of PCP or 2,4-DCP decreased. This finding suggests that a relatively low and realistic aqueous concentration of these compounds is necessary to more accurately determine their BCF values in natural aquatic environments. Conventional BCF experiments at higher aqueous concentrations may underestimate the BCF values.