Toxicity to fish

For several important parameters relating to the effects of environmental pollutants (especially regarding human health) no validated QSAR models of sufficient predictive capacity are yet available  

Fish represent a high level in aquatic foodwebs and as such are important indicators of the status of aquatic ecosystems. A variety of freshwater fish species are frequently used for testing (estuarine or marine species are rarely considered)  

Survival, growth, behavioural and physiological changes are used as quantifiable effects in toxicity tests with fish in the laboratory. Acute toxicity is generally described in terms of the LC50 (LC lethal concentration) - that is, the level of the toxicant (mg/1) that is lethal for 50% of the individuals within a defined exposure period, regardless of how mortality is evoked. 

With regard to standard test endpoints, the differences between fish species may be smaller than is sometimes supposed (Sprague, 1970). The various LC50 test procedures for fish generally result in a coincident relative ranking of the toxicants that is, the most toxic compound is always the most toxic, intermediates remain the intermediates and the least-toxic compound is always the least toxic, provided that the physical and chemical test parameters are kept constant. Absolute LC50 values are generally more dependent on the specific test set-up than on the inherent sensitivity of the fish species. Various factors may influence the absolute values of the observed toxic concentrations  

Life stage of the species the toxicity of xenobiotics towards organisms varies with the age relative to lifespan and the sex, size, lipid content, etc. of the species. 

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The effects of pollution can be direct, such as toxic emissions providing a fatal dose of toxicant to fish, animal life, and even human beings. The effects also can be indirect. Toxic materials which are nonbiodegradable, such as waste from the manufacture of insecticides and pesticides, if released to the environment, are absorbed by bacteria and enter the food chain. These compounds can remain in the environment for long periods of time, slowly being concentrated at each stage in the food chain until ultimately they prove fatal, generally to predators at the top of the food chain such as fish or birds. 

The xylenes are mildly toxic. They ate mild skin irritants, and skin protection and the cannister-type masks are recommended. The oral LD q value for rats is 4300 ppm. The STEL for humans is 150 ppm. Xylenes show only mild toxicity to fish, and the threshold limit for crop damage is 800—2400 ppm. Biodegradation with activated seed is slow, and sewage digestion is impaired by 0.1% concentrations. In the event of a spih, oil-skimming equipment, adsorbent foam, and charcoal maybe used for cleanup. 

In the area of municipal and iadustrial wastewater treatment, the principal environmental issue is the toxicity of residual flocculating agents ia the effluent. Laboratory studies have shown that cationic polymers are toxic to fish because of the iateraction of these polymers with giU. membranes. Nonionic and anionic polymers show no toxicity (82,83). Other studies have shown that ia natural systems the suspended inorganic matter and humic substances substantially reduce the toxicity of added cationic polymer, and the polymers have been used successfully ia fish hatcheries (84—86). Based on these results, the EPA has added a protocol for testing these polymers for toxicity toward fish ia the presence of humic acids (87). The addition of anionic polymers to effluent streams containing cationic polymers to reduce their toxicity has been mentioned ia the patent Hterature (83). 

The mode of action has not yet been elucidated but the manufacturer states that it probably behaves like the herbicide triflurolin and its congeners. These materials inhibit cell division by binding to tubuHn thereby internipting micro-tubule development. This, in turn, stops spindle fiber formation essential to mitosis and cell division. Experiments with C-labeled Prime+ show that it is acutely toxic to fish with estimated LC q (96 h) of less than 100 ppb for rainbow trout and bluegiU. sunfish. However, channel catfish did not exhibit any toxic response at the maximum attainable water concentration (10). 

Inabenfide. [4-Chloro-2-(a-hydroxybenzyl)]-isonicotonanilide) [82211 -24-3] (Inabenfide) (32) is not for use in the United States, but is used in other countries to inhibit the growth of rice plants. The compound is appHed to the soil 40—60 days prior to the heading up of plants, where it is absorbed through the roots and translocated throughout the stem. It inhibits the elongation of the lower intemodes and this stops lodging. It is extremely toxic to fish. 

DDT is highly toxic to fish (LC q for trout and blue gill, 0.002—0.008 ppm), and it is only moderately toxic to birds (oral LD q mallard 1300 and pheasant >2240 mg/kg). However, widespread bird kills have resulted from bioconcentration of DDT through food chains, ie, from fish or earthworms. A significant environmental problem has resulted from the specific effects of DDE on eggshell formation in raptorial birds where accumulation has caused decreases in shell thickness of 10—15%, resulting in widespread breakage. 

Endrin [72-20-8] is l,2,3,4,10,10-hexachloro-l,4,4t ,5,8,8t -hexahydro-6,7-epoxy-l,4- <7o, <7o-5,8-dimethanonaphthalene (35) (mp 245 dec, vp 0.022 mPa at 25°C) and is soluble in water to 23 / g/L. It is produced by a Diels-Alder reaction of hexachloronorbomadiene with cyclopentadiene, followed by epoxidation. This reaction produces the endo,endo isomer of dieldrin, which is less stable and more toxic with rat LD q values of 17.8 and 7.5 (oral) and 15 (dermal) mg/kg. It is used as a cotton insecticide but because of its high toxicity to fish it has been restricted. 

Phenol fumes are irritating to the eyes, nose, and skin. According to the National Institute for Occupational Safety and Health (NIOSH), exposure to phenol should be controUed so that no employees are exposed to phenol concentrations >20 mg/m, which is a time-weighted average concentration for up to a 10-h work day, 40-h work week. Phenol is very toxic to fish and has a nearly unique property of tainting the taste of fish if present in marine... 

Environmentally, these aLkanolamines present little problem. Only AMP has been studied extensively, but it was found to be degradable, to be of low toxicity to fish and microorganisms, and to be nonaccumulative. TRIS AMINO has been added to water used to ship fish in order to improve viabiUty. 

Toxicity to fish is included in the data Hsted in Table 4. Marine life, particularly fish, may suffer damage from spills in lakes and streams. The chlorobenzenes, because they are denser than water, tend to sink to the bottom and may persist in the area for a long time. However, some data indicate that dissolved 1,2,4-trichlorobenzene can be biodegraded by microorganisms from wastewater treatment plants and also has a tendency to slowly dissipate from water by volatilization (34). 

Environmental. The toxicity of cyanide in the aquatic environment or natural waters is a result of free cyanide, ie, as HCN and CN . These forms, rather than complexed forms such as iron cyanides, determine the lethal toxicity to fish. Complexed cyanides may revert to free cyanide under uv radiation, but the rate is too slow to be a significant toxicity factor. Much work has been done to estabhsh stream and effluent limits for cyanide to avoid harmful effects on aquatic life. Fish are extremely sensitive to cyanide, and the many tests indicate that a free cyanide stream concentration of 0.05 mg/L is acceptable (46), but some species are sensitive to even lower concentrations. 

Toxicity. Low toxicity from solvent-vapor inhalation or skin contac t is preferred because of potential exposure during repair of equipment or while connections are being broken after a solvent transfer. Also, low toxicity to fish and bioorganisms is preferred when extraction is used as a pretreatment for wastewater before it enters a biotreatment plant and with final effluent discharge to a stream or lake. Often solvent toxicity is low if water solubility is high. 

Materials that demonstrate unusual reactivity with water are identified as and materials that possess oxidizing properties shall be identified by the letters Z. Other special hazard symbols may be used to identify radioactive hazards, corrosive hazards, substances that are toxic to fish, and so on. 

Aeration of the hypolimnion (lower, colder layer of water in a stratified lake) without disruption of stratification has been used in deep lakes. This has the advantage of not increasing the temperature of the hypolimnion and prevents the advection of nutrient-rich water into the epilimnion (upper, warmer layer of water in a stratified lake). Oxygen injection is preferred in order to prevent the build up of nitrogen super-saturation which is toxic to fish. "... 

The acute oral toxicity (mice), skin and eye irritation (rabbits), sensitization (rabbits), and toxicity to fish were determined for the three detergent formulations and were found to be no more severe than those obtained for LAS [46] and phosphate-containing commercial detergents. 

Some data on cyclodiene toxicity is presented in Table 5.9. Aldrin and dieldrin have similar levels of acute toxicity indeed, the toxicity of aldrin has been largely attributed to its stable metabolite, dieldrin. Dieldrin is highly toxic to fish, mammals. 

Ecotoxological properties Acute toxicity to fish Acute toxicity to Daphnia Biodegradability Hydrolysis (abiotic degradability)... 

Ecotoxological Algal growth inhibition 21 day Daphnia toxicity Prolonged toxicity to fish Bioaccumulation in fish Prolonged biodegradation Effect on higher plants Effect on earthworms... 

Suberitine, a small protein from the sponge Suberites domcuncula, has a variety of actions. It is not very toxic but causes hemolysis in human erythrocytes, flaccid paralysis in crabs and depolarization of squid axon and abdominal nerve of crayfish. A variety of extracts from Porifera have been shown to be toxic to fish and generally have cytotoxic and hemolytic actions (62,63). As discussed previously, a variety of sponges exude substances that are toxic to fish. 

Spry DJ, Wiener JG. 1991. Metal bioavailabihty and toxicity to fish in low-alkalmity lakes a critical review. Environ PoUut 71 243-304. 

In aquatic systems dissolved aluminum species are toxic to fish. There exists a vast number of aluminum species, ranging from inorganic monomeric to complex colloidal. polymeric and organic complexes. A major problem, when studying aluminum species in water is that the species quickly convert one into the other (Fairman and Sanz-Medel 1995). 

PHMB is very toxic to fish and aquatic life. It is moreover irritating to skin and may cause sensitization by skin contact. It can cause irritation to the eyes, nose and respiratory tract. The PHMB is not compatible with most common swimming pool chemicals. Not compatible with chlorine and chlorinated chemicals and bromine donors. Not compatible with ionic sterilizers, copper based QAC-algicides, anionic detergents, water softening chemicals, persulfate oxidants etc. The defence of the inventors of PHMB is that one should not combine it with other biocides because it should be a bactericide/algicide. But the algicidal properties of PHMB are very weak in brochures and manuals the dose is 200 ppm. 

Table 4.8. Acute toxicity to fish of some pesticides dissolved in water (FC50, mkg/l) [30]...

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