In Vivo Biotransformation Rates of Organic Chemicals in Fish: Relationship with Bioconcentration and Biomagnification Factors

Abstract

In vivo dietary bioaccumulation experiments for 85 hydrophobic organic substances were conducted to derive the in vivo gastrointestinal biotransformation rates, somatic biotransformation rates, bioconcentration factors (BCF), and biomagnification factors (BMF) for improving methods for bioaccumulation assessment and to develop an in vivo biotransformation rate database for QSAR development and in vitro to in vivo biotransformation rate extrapolation. The capacity of chemicals to be biotransformed in fish was found to be highly dependent on the route of exposure. Somatic biotransformation was the dominant pathway for most chemicals absorbed via the respiratory route. Intestinal biotransformation was the dominant metabolic pathway for most chemicals absorbed via the diet. For substances not biotransformed or transformed exclusively in the body of the fish, the BCF and BMF appeared to be closely correlated. For substances subject to intestinal biotransformation, the same correlation did not apply. We conclude that intestinal biotransformation and bioavailability in water can modulate the relationship between the BCF and BMF. This study also supports a fairly simple rule of thumb that may be useful in the interpretation of dietary bioaccumulation tests; i.e., chemicals with a BMF of <1 tend to exhibit BCFs based on either the freely dissolved (BCF) or the total concentration (BCF) of the chemical in the water that is less than 5000.

Comparison of laboratory-derived biomagnification factors for hexachlorobenzene in common carp conducted under 9 test conditions

“…More recently, Lo et al [14] investigated the relationship between BCF and BMF using 85 hydrophobic organic substances. More recently, Lo et al [14] investigated the relationship between BCF and BMF using 85 hydrophobic organic substances.…”

“…Based on these equations, the BMF kg of a chemical with a BCF L of 5000 would be 0.11 with a 95% CI of 0.040 to 0.28, and the 5% lipid-normalized BMF kg of a chemical with a BCF L of 5000 would be 0.10 with a 95% CI of 0.036 to 0.28. More recently, Lo et al [14] investigated the relationship between BCF and BMF using 85 hydrophobic organic substances. They found that for substances not biotransformed or transformed exclusively in the body of the fish, the BCF and BMF appeared to be closely correlated.…”

“…They found that for substances not biotransformed or transformed exclusively in the body of the fish, the BCF and BMF appeared to be closely correlated. For substances subject to intestinal biotransformation, the same correlation did not apply [14]. When evaluating the relationship between BCF and BMF values, it is important to consider the differences in chemical accumulation, metabolism, and overall fate for chemicals attributable to the mode of uptake (water vs food).…”

“…The endpoint in this new test is the biomagnification factor (BMF), which is considered to be a meaningful measure of the potential for a chemical to undergo dietary biomagnification in the environment [5,6]. However, there are as yet limited experimental BMF data, and many researchers and regulators are still trying to identify appropriate strategies for assessing the bioaccumulation potential of chemicals using dietary exposure tests [10][11][12][13][14]. However, there are as yet limited experimental BMF data, and many researchers and regulators are still trying to identify appropriate strategies for assessing the bioaccumulation potential of chemicals using dietary exposure tests [10][11][12][13][14].…”

“…The OECD conducted a ring test for the dietary exposure bioaccumulation fish test to confirm the validity of the test before officially adopting it [8,9]. However, there are as yet limited experimental BMF data, and many researchers and regulators are still trying to identify appropriate strategies for assessing the bioaccumulation potential of chemicals using dietary exposure tests [10][11][12][13][14].…”