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

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Regulatory Science

Background:

• Japan's Chemical Substances Control Law adopted the OECD Test Guideline No. 305 bioaccumulation fish test in 2018.
• The current criterion for non-high bioaccumulation (BMF_Kg < 0.007) may be overly restrictive, potentially hindering new chemical substance development.
• This study addresses concerns that the existing criterion is too restrictive, rather than scientifically uncertain.

Purpose of the Study:

• To propose expanded criteria for determining substances that are not highly bioaccumulative.
• To facilitate the approval of newly developed chemical substances by reducing regulatory burdens.
• To reassess the bioaccumulation threshold based on statistical analysis of biomagnification factors.

Main Methods:

• Utilized statistical post-processing techniques to evaluate expanded bioaccumulation criteria.
• Proposed a two-condition criterion based on the ratio of biomagnification factors (BMF_5%) and probabilistic assessment of future measurements.
• Defined specific conditions: BMF_5% ratio < 3.0 and >95% probability of the next BMF_5% being < 0.0334 for non-ionizable lipid-soluble compounds.

Main Results:

• The proposed statistical approach suggests an increase in the criterion for not being highly bioaccumulative.
• Application of the new approach implies the threshold could rise from 0.007 to 0.0149.
• The revised criteria aim to provide a more nuanced assessment of bioaccumulation potential.

Conclusions:

• The study presents a statistically-supported method to revise the bioaccumulation criterion in Japan.
• The proposed criteria could potentially increase the number of chemical substances deemed not highly bioaccumulative.
• This revised approach may help streamline the regulatory process for new chemical substances.