Chapter 8
Coefficient of Assessment for the Microcosm
System
Kunihiko Kakazu, Kakeru Ruike, and Kazuhito Murakami
Abstract In this chapter, the concept of the coefficient of assessment and the
limitations of the correlative analysis of the microcosm and mesocosm are described.
8.1 Coefficient of Assessment
A conceptual diagram of the unevenness of the NOEC in the same test material in the
microcosm test is shown in Fig. 8.1. When ecosystemic sensitivity is assumed to be
normally distributed, and because the sensitivity varies according to the exposure of
the ecosystem to the same chemical substance and demand, the standard deviation
(σ) of the sensitivity distribution from experimental data is equal to 0.51. In other
words, the density that only σ moved the mean is equivalent to density to protect
ecosystemic 84%. When the standard deviation of the regression lines of both the
correlation of the NOEC in the microcosm test and the NOAEC in the outdoor
ecosystem test (i.e., the mesocosm test) is equal to 0.57, the range over which only σ
moved the regression line downward may account for 84% of the chemical substance. Meanwhile, a conceptual diagram of the unevenness of the NOEC in a
different test material is shown in Fig. 8.2.
The validity of the toxicity evaluation using the microcosm test was examined
from the relationship between the NOEC in the microcosm and the average value of
the NOEC in the natural ecosystem. It was indicated that 23 out of 26 substances fell
within the confidence interval of the regression line, and a strong correlation between
K. Kakazu
Foundation for Advancement of International Science, Tsukuba, Ibaraki, Japan
e-mail: kakazu@fais.or.jp
K. Ruike
University of Tsukuba/Foundation for Advencement of International Science, Tsukuba, Ibaraki,
Japan
e-mail: ruike@fais.or.jp
K. Murakami (*)
Chiba Institute of Technology, Narashino, Chiba, Japan
e-mail: kazuhito.murakami@p.chibakoudai.jp
© Springer Nature Singapore Pte Ltd. 2020
Y. Inamori (ed.), Microcosm Manual for Environmental Impact Risk Assessment,
https://doi.org/10.1007/978-981-13-6798-4_8
159
Coefficient of Assessment for the Microcosm
System
Kunihiko Kakazu, Kakeru Ruike, and Kazuhito Murakami
Abstract In this chapter, the concept of the coefficient of assessment and the
limitations of the correlative analysis of the microcosm and mesocosm are described.
8.1 Coefficient of Assessment
A conceptual diagram of the unevenness of the NOEC in the same test material in the
microcosm test is shown in Fig. 8.1. When ecosystemic sensitivity is assumed to be
normally distributed, and because the sensitivity varies according to the exposure of
the ecosystem to the same chemical substance and demand, the standard deviation
(σ) of the sensitivity distribution from experimental data is equal to 0.51. In other
words, the density that only σ moved the mean is equivalent to density to protect
ecosystemic 84%. When the standard deviation of the regression lines of both the
correlation of the NOEC in the microcosm test and the NOAEC in the outdoor
ecosystem test (i.e., the mesocosm test) is equal to 0.57, the range over which only σ
moved the regression line downward may account for 84% of the chemical substance. Meanwhile, a conceptual diagram of the unevenness of the NOEC in a
different test material is shown in Fig. 8.2.
The validity of the toxicity evaluation using the microcosm test was examined
from the relationship between the NOEC in the microcosm and the average value of
the NOEC in the natural ecosystem. It was indicated that 23 out of 26 substances fell
within the confidence interval of the regression line, and a strong correlation between
K. Kakazu
Foundation for Advancement of International Science, Tsukuba, Ibaraki, Japan
e-mail: kakazu@fais.or.jp
K. Ruike
University of Tsukuba/Foundation for Advencement of International Science, Tsukuba, Ibaraki,
Japan
e-mail: ruike@fais.or.jp
K. Murakami (*)
Chiba Institute of Technology, Narashino, Chiba, Japan
e-mail: kazuhito.murakami@p.chibakoudai.jp
© Springer Nature Singapore Pte Ltd. 2020
Y. Inamori (ed.), Microcosm Manual for Environmental Impact Risk Assessment,
https://doi.org/10.1007/978-981-13-6798-4_8
159