Chemical substances environmental fate

Cronin MTD, Walker JD, Jaworska JS, et al. (2003) Use of quantitative structure-activity relationships in international decision-making frameworks to predict ecological effects and environmental fate of chemical substances. Environmental Health Perspectives IT. 1376-1390. 

The physical behavior of a chemical determines how the chemical partitions among the various environmental media and has a large effect on the environmental fate of a substance. For example, the release into soil of two different acids (with similar chemical behavior) may result in one chemical mainly volatilizing into the air and the other chemical becoming mainly sorbed to the organic fraction of the soil. The physical behavior of a substance therefore can have a large effect on the environmental fate of that substance. 

Besides the fugacity models, the environmental science literature reports the use of models based on Markov chain principle to evaluate the environmental fate of chemicals in multimedia environment. Markov chain is a random process, and its theory lies in using transition matrix to describe the transition of a substance among different states [39,40]. If the substance has all together n different kinds of states,... 

Substance Chemical Structure Uses/Origin Environmental Occurrence Environmental Fate... 

EPA (1975) Review of the environmental fate of selected chemicals. US Environmental Protection Agency, Office of Toxic Substances, Washington, EPA-560/5-75-001... 

Environmental fate Chemicals released in the environment are suscephble to several degradahon pathways, including chemical (i.e., hydrolysis, oxidation, reduction, dealkylahon, dealkoxylation, decarboxylahon, methylation, isomerization, and conjugation), photolysis or photooxidahon and biodegradation. Compounds transformed by one or more of these processes may result in the formation of more toxic or less toxic substances. In addihon, the transformed product(s) will behave differently from the parent compound due to changes in their physicochemical properties. Many researchers focus their attention on transformahon rates rather than the transformahon products. Consequently, only limited data exist on the transitional and resultant end products. Where available, compounds that are transformed into identified products as weh as environmental fate rate constants and/or half-lives are listed. 

Water solubility and vapor pressures of PFOS and PFOA are given in Table 2. These data were obtained from products that were not refined and as a result may contain more than one PFA such that these data may not be representative of the pure compounds, especially in environmental media. Due to the lack of accurate information on the physico-chemical properties, accurate prediction of the environmental fate and transport of most perfluoroalkyl substances has not yet been possible. The prediction of the distribution and ultimate fates of perfluoroalkyl substances is further complicated by their hydrophobic and lipophobic properties, such that the fugacity approach that has been useful in describing the environmental fates of organochlorines is less useful for describing the environmental fate of PFAs and their precursors. The bulk of the available physical and chemical information is for PFOS... 

Expanding the scope of FIFRA/GLP to include environmental and chemical fate studies will take time. It will mean that studies described by EPA Hazard Evaluation Division, Office of Pesticide and Toxic Substances,for Environmental Fate and Residue Chemistry must meet the requirements outlined in the FIFRA/GLPs, and that... 

The ability to predict the behavior of a chemical substance in a biological or environmental system largely depends on knowledge of the physical-chemical properties and reactivity of that compound or closely related compounds. Chemical properties frequently used in environmental assessment include melting/boiling temperature, vapor pressure, various partition coefficients, water solubility, Henry s Law constant, sorption coefficient, bioconcentration factor, and diffusion properties. Reactivities by processes such as biodegradation, hydrolysis, photolysis, and oxidation/reduction are also critical determinants of environmental fate and such information may be needed for modeling. Unfortunately, measured values often are not available and, even if they are, the reported values may be inconsistent or of doubtful validity. In this situation it may be appropriate or even essential to use estimation methods. 

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