are made possible by the expansion of the database, which is the basis for the
analyses shown in this manual and which is necessary for expanding the applicable
range and optimization of the test method. A close inspection of the assessment
factor reinforced in this manual has already been completed.
In the future, the microcosm test will be established as a practical ecosystem
impact assessment technique, replacing the mesocosm test by further grouping
chemical substances after having thoroughly investigated their characteristics.
Because it is anticipated that the correlation between natural ecosystems and microcosms is high, it is thought that the estimated NOEC is more realistic than that
derived from evaluations using single-species. It currently remains difficult to omit
the test methods for algae, crustaceans, and fish represented by the WET test in the
ecosystem impact assessments of chemical substances. However, by using a parallel
ecosystem model that includes a food chain and energy flow, it becomes possible to
accumulate knowledge, such as that related to the degradability and residual properties of chemical substances, and the recovery and collapse of ecosystem functions.
In other words, it may be said that the superiority of the microcosm is enhanced by
quantifying and evaluating ecosystem impacts. The WET test is a docimasy for
evaluating toxicity that includes combined influences by testing water containing
multiple chemical substances, but it is a single-species test that does not allow for the
evaluation of individual chemical substances. Although it uses species in different
niches in the food chain for an assay, it must be noted that the WET test has a
problem when testing under conditions in which there are interactions among
material circulations, energy flow, and biological interaction, which are the foundations of natural ecosystems. The microcosm, which is a system of multiple,
coexisting species, evaluates the risk of chemical substances at an ecosystem level,
and the safety factor is obtained from the results of research on the correlation
between the conventional mesocosm test and microcosm test before the PNOEC
can be calculated from the accumulation of further data. The merit to the regulations
of the chemical industry is remarkable.
The need for evaluating the introduction of chemical substances in model ecosystems has been noted by the OECD and other chemical substance management
entities, and regulatory laws and model systems are being developed. However, an
international standard for ecosystem impact assessments using mesocosms and
microcosms has yet to be undertaken. The methods described in this book allow
for the influence of chemical substances on ecosystems to be evaluated in the
microcosm, and the effects on the human body, by using marmots and mice, were
demonstrated using the microcosm N-system. It is possible to determine that there is
no risk to the ecosystem by the docimasy, analysis, and evaluation of the NOEC
described in this book. Because a standardized microcosm test could be constructed,
this approach should be utilized globally.
12 Further Perspectives
209
analyses shown in this manual and which is necessary for expanding the applicable
range and optimization of the test method. A close inspection of the assessment
factor reinforced in this manual has already been completed.
In the future, the microcosm test will be established as a practical ecosystem
impact assessment technique, replacing the mesocosm test by further grouping
chemical substances after having thoroughly investigated their characteristics.
Because it is anticipated that the correlation between natural ecosystems and microcosms is high, it is thought that the estimated NOEC is more realistic than that
derived from evaluations using single-species. It currently remains difficult to omit
the test methods for algae, crustaceans, and fish represented by the WET test in the
ecosystem impact assessments of chemical substances. However, by using a parallel
ecosystem model that includes a food chain and energy flow, it becomes possible to
accumulate knowledge, such as that related to the degradability and residual properties of chemical substances, and the recovery and collapse of ecosystem functions.
In other words, it may be said that the superiority of the microcosm is enhanced by
quantifying and evaluating ecosystem impacts. The WET test is a docimasy for
evaluating toxicity that includes combined influences by testing water containing
multiple chemical substances, but it is a single-species test that does not allow for the
evaluation of individual chemical substances. Although it uses species in different
niches in the food chain for an assay, it must be noted that the WET test has a
problem when testing under conditions in which there are interactions among
material circulations, energy flow, and biological interaction, which are the foundations of natural ecosystems. The microcosm, which is a system of multiple,
coexisting species, evaluates the risk of chemical substances at an ecosystem level,
and the safety factor is obtained from the results of research on the correlation
between the conventional mesocosm test and microcosm test before the PNOEC
can be calculated from the accumulation of further data. The merit to the regulations
of the chemical industry is remarkable.
The need for evaluating the introduction of chemical substances in model ecosystems has been noted by the OECD and other chemical substance management
entities, and regulatory laws and model systems are being developed. However, an
international standard for ecosystem impact assessments using mesocosms and
microcosms has yet to be undertaken. The methods described in this book allow
for the influence of chemical substances on ecosystems to be evaluated in the
microcosm, and the effects on the human body, by using marmots and mice, were
demonstrated using the microcosm N-system. It is possible to determine that there is
no risk to the ecosystem by the docimasy, analysis, and evaluation of the NOEC
described in this book. Because a standardized microcosm test could be constructed,
this approach should be utilized globally.
12 Further Perspectives
209