(LC 50 ). Lethal responses appear within a short time, reflecting acute toxicity.
Physiological effects on reproduction (proliferation), behavior, teratogenicity, and
mutagenicity are felt with chronic poisons. Chronic poisoning is evaluated from the
concentration of the effect of exposure to chemical substances over a long period of
time by generations, such that abnormalities appear even if an organism
(or population) does not die. From this influence, the maximum no-effect concentration (NOEC) is calculated, and the reference value and target value are calculated
by multiplying this effect concentration by the uncertainty factor (safety factor). This
is the basis of biological response tests performed in laboratory settings.
Organisms used for response testing in Japan are a green alga
(Pseudokirchneriella subcapitata), a crustacean (Ceriodaphnia dubia), and a fish
(Danio rerio). These were present at the concentration under which chronic toxicity
appears. As drainage is discharged into public waters, it is diluted at least ten times
over, so we assumed a safety factor of 10. Considering the susceptibility of each
species, we assumed that the effect of species differences was 10. It is common to
multiply the dilution ratio and the species difference to 100.
However, repeating biological response tests for many organisms using a single
organism many times cannot accurately reflect the impact when incorporating
interactions among species in ecosystems. The impact evaluation method that
partitions natural ecosystems is called “coral,” and the experimental method that
uses outdoor rivers and ponds to simulate nature is called a “mesocosm,” and both of
them are often used in ecological impact experiments. These methods are laborintensive, exhibit low reproducibility, and are extremely difficult to apply to evaluations of targeted effects.
The microcosm covered in this book considers a combination of many species
and uses flask-scale experiments, so that many experiments can be performed at the
same time. The microorganisms constituting this microcosm include four kinds of
bacteria (as decomposers), one kind of protozoan ciliate, two kinds of metazoan
rotifers, one type of metazoan oligochaete (as a consumer), and two kinds of green
algae and one type of blue-green alga (as producers) in which reproducibility and
stability are excellent, and dynamic equilibrium is established among the species.
Dynamic equilibrium can be obtained in a short period of time even if transplantation
is performed. The effects of chemical substances and foreign microorganisms can be
evaluated from the deviations from this dynamic equilibrium. Until now, as the
Chairman of the Biological Response Test Study Committee of the Ministry of the
Environment of Japan, I have been establishing standards related to biotoxicity tests,
such as the WET test. I believe that evaluating the impacts of chemical and
microorganismic toxins to ecosystems is extremely important.
Experimental results of the microcosm shown in this book provide many examples of the microbial phases constructed, as mentioned above. Based on this, there is
a high possibility of further development of this methodology. Biological response
x
Recommendation
Physiological effects on reproduction (proliferation), behavior, teratogenicity, and
mutagenicity are felt with chronic poisons. Chronic poisoning is evaluated from the
concentration of the effect of exposure to chemical substances over a long period of
time by generations, such that abnormalities appear even if an organism
(or population) does not die. From this influence, the maximum no-effect concentration (NOEC) is calculated, and the reference value and target value are calculated
by multiplying this effect concentration by the uncertainty factor (safety factor). This
is the basis of biological response tests performed in laboratory settings.
Organisms used for response testing in Japan are a green alga
(Pseudokirchneriella subcapitata), a crustacean (Ceriodaphnia dubia), and a fish
(Danio rerio). These were present at the concentration under which chronic toxicity
appears. As drainage is discharged into public waters, it is diluted at least ten times
over, so we assumed a safety factor of 10. Considering the susceptibility of each
species, we assumed that the effect of species differences was 10. It is common to
multiply the dilution ratio and the species difference to 100.
However, repeating biological response tests for many organisms using a single
organism many times cannot accurately reflect the impact when incorporating
interactions among species in ecosystems. The impact evaluation method that
partitions natural ecosystems is called “coral,” and the experimental method that
uses outdoor rivers and ponds to simulate nature is called a “mesocosm,” and both of
them are often used in ecological impact experiments. These methods are laborintensive, exhibit low reproducibility, and are extremely difficult to apply to evaluations of targeted effects.
The microcosm covered in this book considers a combination of many species
and uses flask-scale experiments, so that many experiments can be performed at the
same time. The microorganisms constituting this microcosm include four kinds of
bacteria (as decomposers), one kind of protozoan ciliate, two kinds of metazoan
rotifers, one type of metazoan oligochaete (as a consumer), and two kinds of green
algae and one type of blue-green alga (as producers) in which reproducibility and
stability are excellent, and dynamic equilibrium is established among the species.
Dynamic equilibrium can be obtained in a short period of time even if transplantation
is performed. The effects of chemical substances and foreign microorganisms can be
evaluated from the deviations from this dynamic equilibrium. Until now, as the
Chairman of the Biological Response Test Study Committee of the Ministry of the
Environment of Japan, I have been establishing standards related to biotoxicity tests,
such as the WET test. I believe that evaluating the impacts of chemical and
microorganismic toxins to ecosystems is extremely important.
Experimental results of the microcosm shown in this book provide many examples of the microbial phases constructed, as mentioned above. Based on this, there is
a high possibility of further development of this methodology. Biological response
x
Recommendation