This is an interview article with Akane Yamakawa, Principal Researcher at the National Institute for Environmental Studies, speaking on August 8, 2025, about the development and significance of environmental reference materials.
Role and Importance of Environmental Reference Materials
Environmental reference materials are "standard samples that guarantee measurement accuracy" and are indispensable for ensuring reliability of measured values in chemical analysis of environmental samples. For example, the Soil Contamination Countermeasures Act stipulates "150 mg or less per kg of soil" for lead and its compounds, but if different laboratories measuring the same soil produce results of 100 mg and 200 mg, judgments regarding standard exceedance would differ. Environmental reference materials prevent such measurement value variations, providing standards where "different institutions and measurers obtain approximately the same results."
Three Factors Causing Measurement Value Variations
Measurement value variations arise from ①instrument differences (individual differences in manufacturing, deterioration, environmental conditions, adjustment deficiencies), ②method differences (preprocessing method and condition differences), and ③human differences (weighing, reagent handling, mixing technique variations). Since "the same situation as cooking from recipes resulting in different tastes depending on the cook" occurs in analytical settings, quality control using environmental reference materials becomes important.
"Urban Dust" Development Case
The currently developing environmental reference material "Urban Dust" uses dust collected on dust collection filters at high-traffic intersections of arterial roads and expressways in Tokyo. It represents a "microcosm of urban atmosphere" containing urban-specific substances including vehicle emission particles, brake dust, worn asphalt, and surrounding soil, developed in response to requests for resumption following discontinuation of the previously distributed similar standard material (NIES CRM No. 28 Urban Air Dust).
Development Process and Technology Transfer
Standard material development requires approximately 5 years, proceeding through ①social needs examination, ②raw material collection, ③homogenization (most critical process), and ④measurement and component value determination. Homogenization achieves "uniform component composition regardless of sampling location" through foreign matter removal, particle size adjustment, careful mixing, and bottling, with balancing homogeneity and practicality being important technical challenges.
The development structure comprises 1 researcher, 2 technical staff, and 1 administrative staff totaling 4 members, following ISO international guidelines while requiring experience and judgment to address the individuality of natural-origin raw materials. Technology inheritance maintains quality and reliability, with team cake celebrations becoming customary upon completion.
History of NIES Environmental Reference Materials
The National Institute for Environmental Studies began distributing Japan's first environmental reference material "Ryobu" (deciduous broadleaf tree with heavy metal concentration properties) in 1979, establishing its position as a pioneer in environmental field standard materials against the backdrop of serious environmental problems due to rapid economic growth. Currently distributing 20 types of standard materials covering diverse media from dust, soil, and biological tissues to human hair and urine.
The article provides detailed introduction to the social mission that environmental reference materials fulfill in supporting measurement reliability and the expertise and passion of researchers and technicians engaged in their development, including Researcher Yamakawa's transition experience from space chemistry to environmental chemistry.