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Svecevicius G Syvokiene J Stasiŭnaite P Mickeniene L 《Environmental science and pollution research international》2005,12(5):302-305
Goal, Scope and Background Chlorite (ClO2ˉ) is a primary decomposition product when chlorine dioxide (ClO2) is added during water treatment; therefore
the toxic effects of both compounds on aquatic organisms are possible. Limited data are available concerning their toxicity
to fish. The aim of this study was to investigate sensitivity of rainbow trout to acute and chronic toxicity of chlorine dioxide
and chlorite, and to estimate the Maximum-Acceptable-Toxicant-Concentration (MATC) of those compounds in fish.
Methods The acute and chronic toxicity of chlorine dioxide and chlorite to larval and adult rainbow trout was investigated in 96-hour
to 20-day laboratory exposures evaluating the wide range spectrum of biological indices under semi-static conditions.
Results and Discussion Median lethal concentration (96-hour LC50) values derived from the tests were: 2.2 mg/l for larvae; 8.3 mg/l for adult fish
and 20-day LC50 for larvae was 1.6 mg/l of chlorine dioxide, respectively. Chlorite was found to be from 48 to 18 times less
acutely toxic to larvae and adult fish, correspondingly. Both chemical compounds induced similar toxic effects in rainbow
trout larvae during chronic tests (they affected cardio-respiratory and growth parameters), but chlorine dioxide had a higher
toxic potency than chlorite. A significant decrease in the heart rate and respiration frequency of larvae was established.
However, within an increase in exposure duration recovery of cardio-respiratory responses was seen to have occurred in larvae
exposed to chlorite. Meanwhile, in larvae exposed to chlorine dioxide, a significant decrease in cardio-respiratory responses
remained during all 20-day chronic bioassays. Chlorine dioxide also more strongly affected growth parameters of rainbow trout
larvae at much lower test concentrations. Decreased rate of yolk-sack resorption occurred only in the tests with chlorine
dioxide.
Conclusions Maximum-Acceptable-Toxicant-Concentration (MATC) of 0.21 mg/l for chlorine dioxide and of 3.3 mg/l for chlorite to fish was
derived from chronic tests based on the most sensitive parameter of rainbow trout larvae (growth rate). According to substance
toxicity classification accepted for Lithuanian inland waters, chlorine dioxide and chlorite can be referred to substances
of \moderate\ toxicity to fish.
Recommendations and Outlook Due to its very reactive nature, chlorine dioxide is rapidly (in a few hours) reduced to chlorite, which is persistent also
as a biocide but 16 times less toxic to fish, according to MATC. Therefore, it is much more likely that fish will be exposed
to chlorite than to chlorine dioxide in natural waters. Presently accepted, the Maximum-Permitted-Concentration of total residual
chlorine (TRC) in waste-water discharging into receiving waters is 0.6 mg/l. If this requirement will not be exceeded, it
is unlikely that fish would be exposed to lethal or even to sublethal concentrations of chlorine dioxide or chlorite. Furthermore,
chlorine dioxide does not generate toxic nitrogenous (chloramines) or carcinogenic organic residuals (trihalomethanes). All
these properties make chlorine dioxide a more promising biocide than chlorine. 相似文献
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Does ecotoxicology really contribute to our knowledge about the function of an ecosystem or environment? Is ecotoxicology really a science of its own? The answers to these questions must be NO. The reasons lie in the origin and past of ecotoxicology.Like medicine, ecotoxicology does not have its own scientific theory, but rather borrows from other disciplines: the scientific theory of medicine is biology, and that of ecotoxicology is ecology and pharmacology. Neither medicine nor ecotoxicology see the normal status and routine function of their objects under study. Ecotoxicology regards the environment as being adversely impacted by anthropogenic noxes, mainly chemicals, perhaps based on a paradigm of permanent guilt.14.
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