Statistical Post-Processing Method for Evaluating Bioaccumulation in Fish Due to Dietary Exposure in Japan.

In 2018, the dietary exposure bioaccumulation fish test of the Organization for Economic Co-operation and Development Test Guideline No. 305 was introduced into Japan's Chemical Substances Control Law. The Japanese government has adopted a single definitive testing criterion for the absence of high bioaccumulation: the growth-corrected kinetic dietary magnification factor (BMFKg) must be less than 0.007. The aim of this study was to decrease regulatory restrictions in order to increase newly developed chemical substances and their subsequent approval of their manufacture and import, i.e., the present study was motivated by concerns over the criterion being too restrictive, rather than scientific concerns, such as uncertainty in criterion. We used statistical post-processing to assess the possibility of expanding the criteria for not being highly bioaccumulative. Based on our results, we proposed the criterion that the test substance should be considered not highly bioaccumulative if the following two conditions are met: (1) The ratio of the maximum to the minimum measured 5% lipid-standardized biomagnification factor at the end of the uptake phase (BMF5%, n = 5) for the test substance and reference substance should be less than 3.0, and (2) For the measured BMF5% of the test substance (n = 5), the probability that the next (the sixth) BMF5% is below 0.0334 should exceed 95% based on statistical post-processing. It is worth noting that the BMF5% values should only be applied for non-ionizable lipid soluble compounds. Application of our suggested approach to Japan implies that the criterion for chemical substances that are not highly bioaccumulative in the dietary exposure bioaccumulation fish test would be increased from 0.007 to 0.0149.

Comparison of bioconcentration and biomagnification factors for poorly water-soluble chemicals using common carp (Cyprinus carpio L.).

Existing regulatory criteria for bioaccumulation assessment of chemicals are mainly based on a bioconcentration factors (BCF) not a biomagnification factors (BMF). We performed dietary exposure tests for nine poorly water-soluble chemicals and developed a linear regression between the 5 % lipid normalized BCF (BCF(L)) and the lipid-corrected BMF (BMF(L)). The BMF(L) of substances with BCF(L) = 5,000 was 0.31 (95 % CI 0.11-0.87), whereas the BCF(L) of substances with BMF(L) = 1 was 13,000 (95 % CI 5,600-30,000). Five substances can be considered very bioaccumulative (vB) according to the BCF end point (BCF > 5,000), but only two substances were recognized to biomagnify according to the BMF end point (BMF ≥ 1). Although our results are highly suggestive of a relationship between BCF and BMF, additional BMF and trophic magnification factor data for chemicals are required to support this relationship, and new techniques (e.g., fugacity approach) may help in resolving the apparent contradiction in hazard categorization.