Improved Method for Estimating Bioconcentration/Bioaccumulation Factor From Octanol/Water Partition Coefficient

Abstract

A compound's bioconcentration factor (BCF) is the most commonly used indicator of its tendency to accumulate in aquatic organisms from the surrounding medium. Because it is expensive to measure, the BCF is generally estimated from the octanol/water partition coefficient (Kow), but currently used regression equations were developed from small data sets that do not adequately represent the wide range of chemical substances now subject to review. To develop an improved method, we collected BCF data in a file that contained information on measured BCFs and other key experimental details for 694 chemicals. Log BCF was then regressed against log Kow and chemicals with significant deviations from the line of best fit were analyzed by chemical structure. The resulting algorithm classifies a substance as either nonionic or ionic, the latter group including carboxylic acids, sulfonic acids and their salts, and quaternary N compounds. Log BCF for nonionics is estimated from log Kow and a series of correction factors if applicable; different equations apply for log Kow 1.0 to 7.0 and >7.0. For ionics, chemicals are categorized by log Kow and a log BCF in the range 0.5 to 1.75 is assigned. Organometallics, nonionics with long alkyl chains, and aromatic azo compounds receive special treatment. The correlation coefficient (r2 = 0.73) and mean error (0.48) for log BCF (n = 694) indicate that the new method is a significantly better fit to existing data than other methods.

Assessment and validation of the CAESAR predictive model for bioconcentration factor (BCF) in fish

“…For the comparison we used the results of predictions for the model developed by Meylan et al . [24,25] and implemented in the BCFBAF v3.00 included into EPI Suite v4.0 [7]. …”

The time- and age-dependent effects of the juvenile hormone analog pesticide, pyriproxyfen on Daphnia magna reproduction

“…Pyriproxyfen is also relatively lipophilic as it has an octanol/water partitioning coefficient of K ow 5.6 and a bioconcentration factor (BCF) of approximately 1500 in fish (Steginsky et al, 1994). Some models predict that pyriproxyfen may have a greater BCF in aquatic organisms with lower metabolic capacity based on its K ow (Meylan et al, 1999; Sullivan and Goh, 2008). The maximum aquatic pyriproxyfen concentrations are estimated to be about 290 pM (93ng L-1) based on a New York State risk assessment (Serafini, 2001), but may approach 1245 pM (400 ng L-1) 24 hours post-spray based on field tests (Schaefer and Miura, 1990).…”

Workgroup Report: Review of Fish Bioaccumulation Databases Used to Identify Persistent, Bioaccumulative, Toxic Substances

“…This computerized database (SRC 2006) is composed of several interrelated files: DATALOG, CHEMFATE, BIOLOG, and BIODEG. DATALOG, the largest file, contains > 325,000 records on > 16,000 chemicals derived from the literature (Meylan et al1999). Categories of data include chemical identification and property information [e.g., chemical name, CAS Registry number, molecular formula, molecular weight, octanol–water partition coefficients ( K ow ), and acid dissociation constant].…”

“…In the absence of reliable empirical BCF or BAF data for organic chemicals with a log K ow > 4.1, predictions from three BCF models and one BAF model are used to assess bioaccumulation. The models used are the SRC BCFWIN QSAR model (Meylan et al 1999), the Mekenyan-Dimitrov POPs model (Dimitrov et al 2005a), and the Gobas-Arnot BCF and BAF models (Arnot and Gobas 2003). …”

“…The EPI Suite contains 11 programs for estimating physical–chemical properties, rate constants, and partition coefficients for organic chemicals; one of these programs is BCFWIN, which is used to estimate the chemical’s BCF based on its K ow and structural features (e.g., functional groups and elemental composition) (Meylan et al 1999). The BCFWIN predictive algorithm is built on a database of 694 chemicals that includes 610 nonionic organic compounds (which include 18 organometallics) and 84 ionic organic compounds (which include carboxylic acids, sulfonic acids and their salts, and quaternary nitrogen compounds).…”