Development and assessment of new risk assessment methods
Title of Research:XXXXDevelopment of a conceptual model for environmental risk assessment ofmicroplastics and a trial risk assessment in Tokyo Bay
Principal Investigator:
Wataru Naito. National Institute of Advanced Industrial Science and Technology (AIST), ResearchInstitute of Science for Safety and Sustainability (RISS), Group Leader
w-naito@aist.go.jp
Collaborators:
Masashi Gamo, AIST, RISS
Kiyotaka Tsunemi, AIST, RISS
Hideo Kajihara, AIST, RISS
Kyoko Ono, AIST, RISS
Isamu Ogura, AIST, RISS
Bin-Le Lin, AIST, RISS
Xue Mianqiang, AIST, RISS
Hiroyuki Mano, AIST, RISS
Yuichi Iwasaki, AIST, RISS
Naohide Shinohara, AIST, RISS
Yuriko Ishikawa, AIST, RISS
Summary of Research:
The purpose of this study project is to review the existing domestic and international literature forenvironmental risk assessment of microplastics (MPs), to develop a conceptual model that concretely
shows the risk assessment procedure of MPs, and to conduct a trial risk assessment for Tokyo Bay. In
FY2022, we established methods for estimating MP loadings from major sources, which isindispensable for considering priorities for source control measures, etc. We estimated loadings for
product-containing MP (PCP), laundry-derived fiber, and tire-wear particles (TWP) entering Tokyo Bay,and showed the range of possible values for the estimates. We investigated to understand the MP
monitoring levels along the Japanese coast (especially in Tokyo Bay) and a method for estimating thedistribution of MP concentrations in the unmeasured range and estimated the distribution of thenumber of unmeasured MP concentrations from available data. We derived an SSD based onhierarchical Bayes using toxicity values listed in the new MP ecotoxicity database. Furthermore, as atrial ecological risk assessment in Tokyo Bay, we compared the corrected MP particle concentrations
in Tokyo Bay with threshold values using Food Dilution as an effect index. Through the environmentalload estimation, analysis of the monitoring data, consideration of data correction methods, and trial
risk assessment in Tokyo Bay, we were able to clarify items with large uncertainties and future
research issues. In the future, we plan to establish an assessment framework that enables us topredict the future environmental burden and risk of MP by improving the accuracy of the estimation
method and understanding the particle size distribution of environmental MP that matches the actualsituation.
Timeline:
March 2020Topics:
JCIA-LRI Annual Workshop “Development of a conceptual model for environmental risk assessment ofDevelopment and assessment of new risk assessment methods
microplastics and a trial risk assessment in Tokyo Bay”, August 2022 (Online)

Publications:
1. Naito W “Risk Assessment in Practice : Opportunities, Challenges and Evolving Roles for Complex
Environmental Issues” SETAC AP 2022, Plenary Speech, Sep. 2022 （Virtual Meeting）
2. Naito W “Development of a conceptual model for environmental risk assessment of microplastics
and a trial risk assessment in Tokyo Bay” MARII Workshop on “Advancements and steps towards aholistic, quantitative risk assessment on microplastics” Oral presentation、 Oct. 2022、Barcelona,
Spain
3. Ueda K, Iwasaki Y, Uesaka M, Naito W “Which concentration unit should be used for environmental
risk assessment of microplastics?” 57th Annual Meeting of Japanese Society of Water Environment,Poster Presentation, March 2023, (Univ. Ehime, Japan)
4. Naito W, Iwasaki Y, Ono K, Ogura I “Framework of environmental risk assessment for microplastics
and an illustrative example” 57th Annual Meeting of Japanese Society of Water Environment, Oral
Presentation, March 2023, (Univ. Ehime, Japan)