No-observed-effect-concentration

Aquatic toxicity is reported in mg/L for Pimepha/espromealas (fathead minnow), 69-h LC q 7650 (17) for Daphnia magna (water flea), 48-h EC q 3310 (18) for Mjriophjllum spicatum (water milfoil), phytotoxicity (EC q for growth) 5962 (19) and for Pana breviceps (frog), no observed effect concentration (NOEC) 400 (20). LC q and EC q are lethal and effect concentrations, respectively, for 50% of the subjects tested. 

Moreover, water quality is to be maintained or restored in such a way that human beings do not suffer any health damage as a result of the pollutant content of the fish they consume. The ecotoxicological data required in order to protect aquatic organisms and fish populations are the so-called No Observed Effect Concentration (NOEC) data. 

Buec. NOEC (No Observed Effect Concentration) Safety Factor... 

The no-observable-effect-concentration (NOEC) for reproduction was 168 mg/kg diet the NOEC for growth was 598 mg/kg. Copper concentrations in whole mites increased significantly at dietary loadings >168 mg/kg... 

TCDD concentrations in eggs of seven species after exposure as fertilized eggs to nominal concentrations of 9-285 ng 2,3,7,8-TCDD/L for up to 540 h. Lowest observed effect concentration (LOEC) in ng/kg FW associated with adverse effects on su rvival or growth 32 days post exposure vs. no observed effect concentration (NOEC) in ng/kg FW Lake herring, Coregonus artedi 270 vs. 175 Fathead minnow, Pimephales promelas ... 

An extensive literature search revealed no published data on famphur toxicity to aquatic animals. Unpublished studies of acute lethality were, however, conducted with the bluegill (Lepomis mac-rochirus) and rainbow trout (Oncorhynchus mykiss). In those studies, the range in LC50 values at 96 h was 18 to 21 mg/L in bluegills and 4.9 to 5.3 mg/L in rainbow trout. The no-observable-effect concentration at 96 h ranged from 14 to 18 mg/1 in bluegills and was 2.1 mg/L in rainbow trout (U.S. Environmental Protection Agency, OPPTS/OPP/EFED/EEB, personal communication, 30 June 1993). 

No observable effect concentration in 28-day 23 early life history exposure... 

Pyrethroids. Unpublished report of Compliance Services International, Rochester and http //ec. europa.eu/sanco pesticides/public/index.cfm. Values presented are lowest reported no observed effect concentrations in pg/L. 

Note (a) BCF is hioconcentration factor, NOEC is no-observed effect concentration. (b) For marine environmental risk assessment, half-life data in freshwater sediment can be overruled by data obtained under marine conditions. (c) Substances are classified when they fulfil the criteria for all three inherent properties for P, B and T. However, there is certain flexibility for instance in cases where one criterion is marginally not fulfilled but the others are exceeded considerably. (d) R48 Danger of serious damage to health by prolonged exposure. ... 

NOEC No-observed effect concentration vPvB Very persistent and very bioaccumulative... 

A subsequent study in the same areas also included biological samples [12]. Again, the Aire river contained the highest concentrations, with total extractable NP + A9PEOi+2 concentrations of 15-76 pg L 1. In many samples of this river, levels exceed the no observed effect concentration (NOEC) for vitellogenin induction in trout (5-20 pg L 1). However, in most samples of the other investigated rivers, levels were... 

For the derivation of the PNEC several approaches have been proposed. Generally these can be categorised into three distinct assessments a conservative, a distributional, and a mixture toxicity approach. In conservative approaches, usually the most (realistic) sensitive endpoint such as LC50 or the known no observed effect concentration (NOEC) is taken and divided by an uncertainty factor (10-100). The selected uncertainty factor value depends on the type of endpoint and the number of available data, and is applied to account for laboratory to field extrapolations, species differences in sensitivities, and similar uncertainties. In distributional approaches, a series of, or all available, literature data are taken and a selected cut-off value is applied to the distribution of these data. The cut-off value may be, e.g., the concentration value that will protect 95% of the species (tested). In general, again an uncertainty factor (usually of 10) is then applied to take into account species differences. In the mixture toxicity approach, a similar mode of action is assumed for the assessment of the combined (additive) effect of the mixture. All relevant mixture components are scaled relative to the most potent one. This results in relative potencies for each component. The total effect of the mixture is then evaluated by... 

SPY sulfapyridine, SDZ sulfadiazine, SMX sulfamethoxazole, SMZ sulfamethazine, SCP sulfachloropyridazine, STZ sulfathiazole, SCT sulfacetamide, AcSMX N -acetylsulfamethoxazole, AcSDM N -acetylsulfadimethoxine, AcSDZ N -acetylsulfadiazine, EC50 Median effective concentration (mg/L), LC50 Median lethal concentration (mg/L), NOEC No-observed-effect concentration (mg/L) LOEC lowest-observed-effect concentration (mg/L), h hours, min minutes, d days... 

The toxicity requirements are established per type of industry, in terms of the maximum number of times the effluents needs to be diluted to produce a no observed effect concentration (NOEC), defined as Gf for fish, Gd for daphnia, Ga for algae, and G1 for luminescent bacteria. Testing is limited to the exposure to only the appropriate Gx level, which should not produce any observed effect [the G-value corresponds with the dilution of the effluent, expressed as the lowest dilution factor (1,2,4,...) causing less than 10% mortality]. The level of maximum allowable toxicity per industrial branch is based on the level that is considered to be attainable with state-of-the-art process and/or treatment technology. Violating the toxicity requirements results in a levy, which makes state-of-the-art compliance a more economic option [12]. 

Reliable chronic toxicity data were available for 21 species of plants (13 phytoplankton and 8 macrophytes) and 15 species of animals. The species sensitivity distributions (SSDs) for atrazine chronic toxicity (no observed effect concentrations [NOECs]) to plants and animals are shown in Figure 4.4. A log-normal distribution model was fitted to each SSD by least-squares regression. 

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