No-observable-effect concentrations NOECs

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. 

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 ... 

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... 

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. 

The environmental concentration of a stressor, either measured or estimated, is compared with an effect concentration such as an LC50 (lethal concentration to kill 50% of individuals in a theoretical population in a set period of time) or no observed effect concentration (NOEC) [31, 32]. These are simple ratios of single exposure and effects values and may be used to express hazard or relative safety. This deterministic method uses point estimates to represent one or more factors in a risk assessment and treats them as if they were fixed and precisely known [33]. The calculation of HQs... 

No-observed-effect concentrations (NOEC) for fish range from 0.3 to 1.1 mg/L for the fathead minnow (64, 66). The most appropriate chronic-toxicity value from the Fairchild et al. (64) study is the 0.7 mg/L value, as... 

TEC, threshold effect concentration, calculated as the geometric mean of the no-observable effect concentration (NOEC) and the lowest-observable effect concentration (LOEC) BA Battery Approach PW porewater WS whole sediments. 

For example, the use of toxicity assays with V. fischeri bacteria and Daphnia magna crustaceans, for which the TU index is 8, gives a No Observed Effect Concentration (NOEC) of 12.5% (Equation 9.1) ... 

Extrapolation from species to communities Responses in communities are inferred from responses in tests conducted with several to many species, such as in the use of SSDs of effect measures, such as no-observed-effect concentrations (NOECs) to extrapolate from laboratory data to communities. Size of the data set and types of organisms tested can influence the representativeness of the laboratory data and the model used to characterize the data. Incorrect combinations of species may confound extrapolation of stressors with specificity of action such as pesticides. 

Within the USEPA s EPI Suite, descriptions of basic physical-chemical properties for 2,4-dichloroaniline (DCA CAS No. 554007), pentachlorophenol (PCP CAS No. 87865), nonylphenol (NP CAS No. 104405), and linear alkylbenzenesulfonate (C12 LAS CAS No. 25155300) were obtained using the EPI Suite (Table 3.1), whereas acute and chronic toxicity estimates for the median effective and chronic effect concentrations (the geometric mean between chronic lowest-observed-effect concentration [LOEC] and no-observed-effect concentration [NOEC]) and for fish, daphnids, and algae for each substance were estimated from ECOSAR (Table 3.2). These compounds were chosen based on their widespread use. 

Walter H, Consolaro F, Gramatica P, Scholze M, Altenburger R. 2002. Mixture toxicity of priority pollutants at no observed effect concentrations (NOECs). Ecotoxicol 11 299-310. 

The TGD provides recommendations for the use of QSARs to predict long term toxicity to fish (no observed effect concentration [NOEC], 28 days) and to Daphnia (NOEC, 21 days). In particular QSARs are provided for chemicals acting by non-polar narcosis and polar narcosis mechanisms of action. No QSARs have been recommended for substances that act by more specific modes of action. For persistence, the TGD recommends two of the SRC BIOWIN models, namely the BIOWIN2 nonlinear model and the BIOWIN3 survey model for ultimate biodegradation. The exact cutoff points for these models have been calibrated on the basis of the model score for 1,2,4-trichlorobenzene — a substance that is known to be relatively persistent under environmental... 

The number produced by a toxicology or ecotoxicology study (e.g., an LD50 or a no-observed-effect concentration [NOEC]). 

A9.3.3.2.1 Chronic toxicity, for purposes of classification, refers to the potential or actual properties of a substance to cause adverse effects to aquatic organisms during exposures which are determined in relation to the life-cycle of the organism. Such chronic effects usually include a range of sublethal endpoints and are generally expressed in terms of a No Observable Effect Concentration (NOEC), or an equivalent ECx. Observable endpoints typically include survival, growth and/or reproduction. Chronic toxicity exposure durations can vary widely depending on test endpoint measured and test species used. 

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