Toxicity environmental organisms

For organic toxic chemicals and their degradation products the number of possibilities is very high. The environmental samples composition usually is very complicated. Unambiguous identification needs serial-pai allel strategy of analysis with many-stage crosschecking of data. 

Laughlin NK University of Wisconsin, Madison, Wl Validate the efficacy of chelation agents such as succimer (dimercaptosuccinic acid, DMSA) not only to reduce body lead stores in young children but also to alleviate neurobehavioral and target organ toxicity (Rhesus monkey) National Institute of Environmental Health Sciences... 

Environmental organic pollutants may be degraded depending on their toxicity, solubility, distribution constant Kow because physical properties of hydrophobic chemicals may affect the solubility and therefore the amount of organic carbon available in the aqueous phase for microbial assimilation and further metabolism (Schwarzenbach and Westall 1981). Chemicals are subject to volatilization and such loss is not assessed in most of the study except for physical transformation and material balance purposes. Polyaromatic hydrocarbons (PAHs) are known to volatilized during incubation even with capping and more then 40% of the initial chemicals could be found lost (Yin and Gu, unpublished data). When proper control was not included and such... 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

New and recycled PVC have been particularly highlighted by environmental organizations (see left), but there are alternatives. Furthermore, most types of plastic will not rot. At the end of their lives, they will end up in a landfill site or in an incinerator where they may produce toxic fumes and residues. Until manufacturers, or other bodies, guarantee a safe disposal or recycling service for these plastic items, they will remain an environmental problem. 

We have addressed the topic of metal bioavailability and metal toxicity in environmental samples. Traditionally, metal availability is investigated using a chemical approach. Afterwards, the concept of Water Effect Ratio (WER) was proposed by the U.S. EPA and employed bioassays (e.g., fish and invertebrate tests) to assess metal bioavailability and toxicity. In the HMBC approach discussed in this review, we have made use of a bacterial assay that is specific for metal toxicity to achieve this goal. This is only a preliminary survey of the potential applications of the HMBC concept. Some preliminary results on the use of MetPLATE for the fractionation of HMBC to obtain information on the factor(s) that control metal bioavailability in environmental samples were also presented. Using MetPLATE eliminates or diminishes the confounding factor represented by the presence of organic toxicants in a given sample. Further work is needed to refine the fractionation scheme. 

Electrochemical methods have been used for determinations of species of elements in natural waters. Of the many electrochemical techniques, only a few have proved to be useful for studies of speciation in complex samples, and to possess the sensitivity required for environmental applications. The greatest concern is the measurement of the toxic fraction of a metal in an aqueous sample. The definition of a toxic fraction of a metal is that fraction of the total dissolved metal concentration that is recognised as toxic by an aquatic organism. Toxicity is measured by means of bioassays. Elowever, a universally applicable bioassay procedure cannot be adopted because the responses of different aquatic species to metal species vary. Nevertheless, bioassays should be used as means of evaluation and validation of speciation methods. A condition is that the test species (of the bioassay) should be very sensitive to the metals being studied so as to simulate a worst case situation (Florence, 1992). 

Studies of long-term exposures in rats and mice have shown that high oral doses of DEHP caused health effects mainly in the liver and testes. These effects were induced by levels of DEHP that are much higher than those received by humans from environmental exposures. Toxicity of DEHP in other tissues is less well characterized, although effects in the thyroid, ovaries, kidneys, and blood have been reported in a few animal studies. The potential for kidney effects is a particular concern for humans because this organ is exposed to DEHP during dialysis and because structural and functional kidney changes have been observed in some exposed rats. 

There are a remarkable number and diversity of activities that have been modeled successfully. The activity to be modeled may be a toxicity to an environmental organism or to man, the fate of a pollutant in an ecosystem, or the pharmacokinetic properties of a xenobiotic in man. To model any of these activities, relevant biological data for the endpoint are required. Chapter 2 describes how toxicological and fate information for chemicals may be obtained from external sources such as the open literature, databases, and the Internet. QSAR developers may also have their own data to model. 

EPA. 1994q. Applicability of Treatment Standards. Uand Disposal Restrictions Phase II - Universal Treatment Standards and Treatment Standards for Organic Toxicity Characteristic Wastes and Newly Listed Wastes. U.S. Environmental Protection Agency. Code of Federal Regulations. 40 CFR 268.40. 

In 1984, a deadly cloud of methyl isocyanate killed thousands of people in Bhopal, India. Shortly thereafter, there was a serious chemical release at a sister plant in West Virginia. These incidents underscored demands by industrial workers and communities in several states for information on hazardous materials. Public interest and environmental organizations around the United States accelerated demands for information on toxic chemicals being released to the environment. Against this backdrop, the Emergency Planning and Community Right-to-Know Act (EPCRA) was enacted in 1986. 

Stewart, A. J. (1984). Interactions between dissolved humic materials and organic toxicants. In Synthetic Fossil Fuel Technologies. Results of Health and Environmental Studies (K. E. Cowser, ed.). Butterworth, London, pp. 505-521. 

Relationships have been found between the adsorption properties described above of surfactants and their environmental effects (toxicity, bioconcentration) on aquatic organisms (algae, fish, rotifers). The log of the EC 50 (the surfactant molar concentration in the water at which the organism population is reduced by 50% relative to a no-dose control) and the log of the BCF (the ratio of surfactant concentration in the fish relative to that in the water) have both been shown (Rosen, 1999, 2001c) to be linearly related to the parameter AG°d/u for a series of anionic, cationic, and nonionic surfactants. The values of asm and AG°d were obtained by the methods described above in Sections IIIB and IIIF, respectively. 

In the hazard assessment of chemicals released into the environment, it is important to evaluate the environmental concentrations of chemicals. Predicted environmental concentrations (PEC) are compared with toxicity data of environmental organisms. Thus, environmental fate models are becoming a valuable tool for the assessment of the potential hazard of chemicals, especially new chemical substances. 

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