Aquatic toxicity persistence

EPA has developed an evaluation tool, the PBT Profiler, which predicts PBT potential of chemicals. The PBT Profiler estimates environmental persistence (P), bioconcentration potential (B), and aquatic toxicity (T) of discrete chemicals based on their molecular structure. It is Internet-based and there is no cost for use. 

Another model, used in the USA, is the OASYS Pollution Prevention Optional Analysis System, developed by the Toxic Use Reduction Institute. Technologies are assessed on a variety of hazard criteria, including acute and chronic human toxicity, physical properties, aquatic impacts, persistence/bioaccumulation, atmospheric releases, disposal, chemical properties, energy/resource use, product hazard and exposure potential. Alternatives are rated to... 

Aquatic toxicity. EDTA has low aquatic toxicity, is not persistent in the environment due mainly to photodegradation of Fe(III), Co(III), and Mn(II) EDTA complexes, does not bioaccumulate, and does not need to be classified and labeled with an environmental symbol or risk phrase. 

The Canadian Environmental Protection Act, 1999 (CEPA 1999) requires the Ministers of the Environment and Health to categorize the substances on the Canadian Domestic Substances List (DSL). The DSL contains 23 000 substances that are subject to categorization (i.e., prioritization). Generally the data selection process involves a search of the scientific literature and databases for quality experimental data for persistence, bioaccumulation potential and inherent toxicity to humans and nonhuman species. If acceptable data are not found, QSARs or other models are used to estimate the persistence, bioaccumulation, and aquatic toxicity of substances based on structure and physical - chemical properties. 

When comparing priority setting methodologies it is important to identify additional external information. For all the methods considered a choice is made by choosing the descriptors. The choice of descriptors is however often based on key parameters from risk assessment schemes or environmental fate models, which makes it less subjective. In the present chapter exposure (given by production volume), aquatic toxicity, bioaccumulation and persistence were chosen as descriptive parameters. For HDT the selection of the descriptors is the main contribution of subjectivity. Additionally, some indirect weighting can be added if the data are separated into classes. 

This book focuses on the chemical persistence and ocotoxicological behavior of pesticides In soil, water, and plants. Recent research data are presented on transport, adsorption and absorption, accumulation, degradation, biological effects, aquatic toxicity, air pollution, exposure, and risk estimation. 

Water quality parameters, such as pH, temperature, hardness, and salinity, can influence the effects of contaminants on aquatic life. The toxicity of TNT decreases slightly with increasing pH and temperature, but is not significantly affected by hardness [39], The persistence of TNT in the environment is limited, and several biological and physical processes (photolysis, hydrolysis) influence its environmental fate [39], The photolysis half-life of TNT appears to be season and latitude dependent, as it ranged from 14 h at latitude 20 in summer to 84 h at latitude 50 in winter in the northern hemisphere [40], The aquatic toxicity of several photo- and biodegradation products of TNT has been studied. Pink water obtained by constant illumination of a TNT solution was more toxic than the TNT solution to P. promelas using... 

A relatively broad variety of aquatic toxicity studies exists for nitro-substituted phenol, toluene, and benzene explosives and related compounds, but very little toxicological information is available for tetryl, cyclic nitramines, and the other energetic compounds discussed in this chapter. Several explosives, such as tetryl, are no longer manufactured and are, therefore, of diminishing environmental concern, although their persistence and the nature, stability, and toxicity of their breakdown products is not understood in sufficient detail and should be further investigated. A variety of other energetic compounds, for example, perchlorates, are used in military operations, and due to environmental concerns with their release, additional studies on their fate and effects in aquatic systems are recommended. 

Ecotoxicity 1,2-Ethanediol is known to be relatively non-persistant (aerobic biodegradation half-lives ranging from 2 to 18 days), and to dispose of low aquatic toxicity. 

Ecotoxicity Similar to 1,2-ethanediol (1.13.). Relatively non-persistant and of low aquatic toxicity (Kent et ak, 1999). 

Based on its physical and chemical properties as well as empirical biodegradation data, DEEP is not expected to degrade quickly in the environment. It is persistent in water, soil, and sediments. It also has the potential to accumulate in organisms and may biomagnify in food chains. The substance has been determined to meet the persistence and bioaccumulation criteria. In addition, aquatic toxicity data indicate that the substance is potentially highly hazardous to aquatic organisms. 

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