Toxicity aquatic organisms

The majority of studies on the acute and chronic toxicity of phthalates to aquatic organisms show no toxic effects at concentrations 200—1000 times the water solubiUty. However, there are some studies iadicatiag higher toxicity which are beheved to be due to the flotation and entrapment effects outlined above. 

Fig. 7. Toxicity of chlorine to aquatic organisms, (a) Time-dependent mortaUty (50%) of four example species in various levels of total residual chlorine in the laboratory, where for A, A.losa aestivalis and B, Salmogairdnerii r (correlation coefficient of the curve) = —0.96 and for C, P/euroneetesplatessa and D, Salmo trutta r = —0.98. (b) A summary of chlorine toxicity to freshwater species, indicating overall no-effect thresholds for acute and chronic exposures. Numbers indicate where more than one test yielded the same result. A different summary figure appHes to marine organisms because of differences in the...

The LC50 is the lethal concentration of chemical (e.g. in air or water) that will cause the death of 50% of the sample population. This is most appropriate as an indicator of the acute toxicity of chemicals in air breathed (or in water, for aquatic organisms). Table 5.11 illustrates the use of LD50 values to rank the toxicity of substances. 

Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment... 

The different oxidation states of a metal can have dramatically different chemical properties, which in turn affect their biogeochemical forms and significance. For example, almost 4 g/L ferrous iron, Fe(II), can dissolve in distilled water maintained at pFi 7.0. However, if the water is exposed to air and the iron is oxidized to Fe(III) essentially all the iron will precipitate, reducing the soluble Fe concentration by more than eight orders of magnitude. Oxidation state can also affect a metal ion s toxicity. For instance, the toxicity of As(III) results from its ability to inactivate enzymes, while As(V) interferes with ATP synthesis. The former is considerably more toxic to both aquatic organisms and humans. 

Hugget D, Brook B, Peterson B, Foran CM, Schlenk D (2002) Toxicity of selected beta adrenergic receptor-blocking pharmaceuticals (B-blockers) on aquatic organisms. Arch Environ Contam Toxicol 43 229-235... 

Data on the toxicity of the various organotin species to aquatic organisms are summarized in Table 23. 

Table 23 Toxicity of organotin compounds to aquatic organisms. ...

Data sets on toxicity to aquatic organisms vary considerably from compound to compound, with dibutyltin being the best studied. Results of toxicity tests for all compounds are summarized in Figure 2. Values for all but one test on the octyltins have been set at the solubility of the compounds, since no toxicity was observed below the solubilities derivation of PNECs for the octyltins are, therefore, more precautionary than for the other compounds. 

Fig. 2. Acute toxicity of organotin compounds to freshwater aquatic organisms.

Hirose A, Takagi A, Nishimura T, Ema M (2004) Review of reproductive and developmentai toxicity induced by organotins in aquatic organisms and experimentai animais. Organohalogen Compounds, 66 3042-3047. 

Turning to the acute toxicity of PAH, terrestrial organisms will be dealt with before considering aquatic organisms, to which somewhat different considerations apply. The acute toxicity of PAHs to mammals is relatively low. Naphthalene, for example, has a mean oral LD50 of 2700 mg/kg to the rat. Similar values have been found with other PAHs. LC50 values of 150 mg/kg and 170-210 mg/kg have been reported, for phenanthrene and fluorene, respectively, in the earthworm. The NOEL level for survival and reproduction in the earthworm was estimated to be 180 mg/ kg dry soil for benzo[a]pyrene, chrysene, and benzoMfluoranthene (Enviromnental Health Criteria 202). 

Berends AG, JC Bouttonet, CG de Rooij, RS Thompson (1999) Toxicity of trifluoroacetate to aquatic organisms. Environ Toxicol Chem 18 1053-1059. 

---