The toxicological screening of the numerous chemicals that we are exposed to requires significant cost and the use of animals. Accordingly, more efficient methods for the evaluation of toxicity are required to reduce cost and the number of animals used. Computational strategies have the potential to reduce both the cost and the use of animal testing in toxicity screening. The ultimate goal of this thesis is to develop computational models for the prediction of toxicological endpoints that can serve as an alternative to animal testing. In Paper I, an attempt was made to construct a global quantitative structure-activity relationship (QSAR)model for the acute toxicity endpoint (LD50 values) using the Munro database that represents a broad chemical landscape. Such a model could be used for acute toxicity screening of chemicals of diverse structures. Paper II focuses on the use of acute toxicity data to support the prediction of chronic toxicity. The results of this study suggest that for related chemicals having acute toxicities within a similar range, their lowest observed effect levels (LOELs) can be used in read-across strategies to fill gaps in chronic toxicity data. In Paper III a k-nearest neighbor (k-NN) classification model was developed to predict human ether-a-go-go related gene (hERG)-derived toxicity. The results suggest that the model has potential for use in identifying compounds with hERG-liabilities, e.g. in drug development.

Sha Ou. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 167-189). / Abstracts in English and Chinese. / abstract --- p.i / 中文摘要 --- p.iv / acknowledgements --- p.vii / Chapter chapter 1. --- introduction --- p.1 / Chapter 1.1 --- Overview --- p.1 / Chapter 1.2 --- Ribosome-inactivating proteins (RIPs) --- p.1 / Chapter 1.2.1 --- Classification --- p.2 / Chapter 1.2.2 --- Structure --- p.3 / Chapter 1.2.3 --- Enzymatic activities --- p.3 / Chapter 1.3 --- Type II RIPs --- p.5 / Chapter 1.3.1 --- Ricin --- p.5 / Chapter 1.3.2 --- Ricinus communis agglutinin (RCA) --- p.6 / Chapter 1.3.3 --- Intracellular mechanism --- p.7 / Chapter 1.3.4 --- Application of RIPs in neuroscience research: suicide axonal transport --- p.10 / Chapter 1.4 --- Type I RIPs --- p.12 / Chapter 1.4.1 --- Trichosanthin (TCS) --- p.12 / Chapter 1.4.2 --- Ricin A chain (RTA) --- p.15 / Chapter 1.4.3 --- Medical applications: immunolesioning and immunotherapy --- p.16 / Chapter 1.5 --- The types of Cell death --- p.17 / Chapter 1.5.1 --- Necrosis --- p.18 / Chapter 1.5.2 --- Apoptosis --- p.18 / Chapter 1.6 --- Inflammations --- p.21 / Chapter 1.6.1 --- Acute inflammation --- p.21 / Chapter 1.6.2 --- Chronic inflammation --- p.22 / Chapter 1.6.3 --- Retinitis --- p.22 / Chapter 1.7 --- Eye model for neurotoxicity studies in CNS --- p.23 / Chapter 1.8 --- Objective of present study --- p.24 / Chapter CHAPTER 2. --- MATERIALS AND METHODS --- p.25 / Chapter 2.1 --- Plan of this chapter --- p.25 / Chapter 2.2 --- Toxins and methods used --- p.25 / Chapter 2.3 --- Animals --- p.26 / Chapter 2.4 --- Preparation of toxin solutions --- p.27 / Chapter 2.4.1 --- RIP solutions --- p.27 / Chapter 2.4.2 --- Labeling type I RIPs with fluorescence --- p.27 / Chapter 2.4.3 --- Control solutions --- p.29 / Chapter 2.5 --- Administrations of solutions --- p.30 / Chapter 2.5.1 --- Basic procedures of vitreous chamber injection --- p.30 / Chapter 2.5.2. --- Injection of trichosanthin (TCS) --- p.31 / Chapter 2.5.3 --- Injection of ricin A chain (RTA) --- p.31 / Chapter 2.5.4 --- Injection of ricinus communis agglutinin (RCA) --- p.32 / Chapter 2.5.5 --- Administration of FITC-TCS --- p.33 / Chapter 2.5.6 --- Administration of FITC-RTA --- p.33 / Chapter 2.6 --- Retinal tissue processing --- p.33 / Chapter 2.6.1 --- Paraffin method --- p.34 / Chapter 2.6.2 --- Cryostatic method --- p.35 / Chapter 2.6.3 --- Electron microscopic method --- p.35 / Chapter 2.7 --- General effects of RIPs on rat retinas --- p.36 / Chapter 2.7.1 --- Hematoxylin-and-eosin staining --- p.36 / Chapter 2.7.2 --- Retinal thickness --- p.37 / Chapter 2.7.3 --- Pathological changes --- p.38 / Chapter 2.7.4 --- Dosage study on TCS --- p.39 / Chapter 2.7.5 --- Statistics --- p.40 / Chapter 2.8 --- Mechanisms of cell death --- p.40 / Chapter 2.8.1 --- Terminal dUTP nick-end labeling (TUNEL) --- p.40 / Chapter 2.8.2 --- Immunohistochemistry for caspase-3 --- p.42 / Chapter 2.8.3 --- Double staining of cleaved caspase-3 and TUNEL --- p.42 / Chapter 2.8.4 --- Electronic microscope observation --- p.43 / Chapter 2.9 --- Entry of type I RIPs into cells --- p.43 / Chapter 2.9.1 --- Propidium iodide staining --- p.43 / Chapter 2.9.2 --- Immunohistochemical localization of Muller cells --- p.44 / Chapter 2.9.3 --- Double staining of Muller cells and TUNEL --- p.44 / Chapter 2.9.4 --- Confocal microscope --- p.44 / Chapter 2.10 --- Reactions of glial cells --- p.45 / Chapter CHAPTER 3. --- RESULTS --- p.47 / Chapter 3.1 --- Preparation of fluorescein-type I RIP conjugates --- p.47 / Chapter 3.1.1 --- Conjugate of FITC-TCS --- p.47 / Chapter 3.1.2 --- Conjugate of FITC-RTA --- p.47 / Chapter 3.2 --- Effects of TCS on retina --- p.47 / Chapter 3.2.1 --- Retina cell count - a dose-dependence study --- p.48 / Chapter 3.2.2 --- Retinal thickness measurement - a time-course study --- p.49 / Chapter 3.2.3 --- Pathological changes --- p.50 / Chapter 3.3 --- Effects of RTA on retina --- p.51 / Chapter 3.3.1 --- Retinal thickness measurement - a time-course study --- p.51 / Chapter 3.3.2 --- Pathological changes --- p.53 / Chapter 3.4 --- Effects of RCA on retina --- p.54 / Chapter 3.4.1 --- Retinal thickness measurement --- p.54 / Chapter 3.4.2 --- Pathological changes --- p.55 / Chapter 3.5 --- Summary of results: general effects of RIPs --- p.56 / Chapter 3.6 --- Cell death - TUNEL method --- p.56 / Chapter 3.6.1 --- TCS experiment --- p.57 / Chapter 3.6.2 --- RTA experiment --- p.58 / Chapter 3.6.3 --- RCA experiment --- p.58 / Chapter 3.7 --- Cell death 一 cleaved caspase-3 immunohistochemistry --- p.58 / Chapter 3.7.1 --- TCS experiment --- p.59 / Chapter 3.7.2 --- RTA experiment --- p.59 / Chapter 3.8 --- EM observation --- p.59 / Chapter 3.8.1 --- TCS experiment --- p.59 / Chapter 3.8.2 --- RTA experiment --- p.60 / Chapter 3.9 --- Summary of results: mode of cell death --- p.60 / Chapter 3.10 --- Localisation of type I RIPs --- p.61 / Chapter 3.10.1 --- FITC-TCS --- p.62 / Chapter 3.10.2 --- FITC-TCS and Muller cell double staining --- p.63 / Chapter 3.10.3 --- Muller cell and TUNEL double staining --- p.64 / Chapter 3.10.4 --- FITC-RTA --- p.64 / Chapter 3.10.5 --- Summary of results: route of intoxication --- p.65 / Chapter 3.11 --- Glial cell reactions after RIP treatment --- p.65 / Chapter 3.11.1 --- TCS experiment --- p.65 / Chapter 3.11.2 --- RTA experiment --- p.66 / Chapter 3.11.3 --- RCA experiment --- p.67 / Chapter 3.11.4 --- Summary of results: glial reactions --- p.67 / Chapter CHAPTER 4. --- DISCUSSION --- p.69 / Chapter 4.1 --- General effects of RIPs on rat retinas --- p.69 / Chapter 4.1.1 --- Effects of trichosanthin (TCS) --- p.69 / Chapter 4.1.2 --- Effects of ricin A chain (RTA) --- p.71 / Chapter 4.1.3 --- Effects of ricinus communis agglutinin (RCA) --- p.73 / Chapter 4.2 --- The mechanisms of cell death --- p.74 / Chapter 4.2.1 --- Cell death caused by TCS --- p.75 / Chapter 4.2.2 --- Caspase-3 and the retina of RCS rat --- p.77 / Chapter 4.2.3 --- Cell death caused by RTA --- p.78 / Chapter 4.2.4 --- Cell death caused by RCA --- p.80 / Chapter 4.2.5 --- Mechanism of RTA - induced necrosis --- p.81 / Chapter 4.3 --- The mechanisms of type I RIPs entering cells --- p.82 / Chapter 4.3.1 --- Transport of TCS in retinal cells --- p.82 / Chapter 4.3.2 --- The uptake of Pure FITC by rat retina --- p.85 / Chapter 4.4 --- Reactions of glial cells --- p.85 / Chapter 4.4.1 --- Glial cell reactions in TCS experiment --- p.86 / Chapter 4.4.2 --- Glial cell reactions in RTA and RCA experiments --- p.87 / Chapter 4.5 --- Possible applications of RIPs on retinal studies --- p.88 / Chapter 4.5.1 --- Potential applications of TCS --- p.88 / Chapter 4.5.2 --- Possible uses of RTA and RCA --- p.90 / Chapter CHAPTER 5. --- CONCLUSIONS --- p.91 / "FIGURES, TABLES, GRAPHS, AND LEGENDS" --- p.93 / APPENDICES --- p.154 / Appendix A Source of materials --- p.154 / Appendix B Dosages for vitreous chamber injection --- p.156 / Appendix C Protocol of conjugate fluorescein to proteins --- p.157 / Appendix D Electronic Microscope methods --- p.160 / Appendix E Histological methods --- p.162 / Appendix F Protocols of TUNEL --- p.163 / Appendix G Protocols of Immunohistochemistry staining --- p.165 / REFERENCES --- p.167

Contaminants may affect marine organisms through various pathways with impacts evident across a variety of spatial and temporal scales. Organisms may encounter short pulsed exposures which contaminate surface waters for hours to days, or more persistent but patchy contamination of benthic habitats throughout their entire life-cycle. This thesis examines the responses of epifauna associated with macroalgae to a pulsed exposure of contaminants (storm-water input) and to chronic contamination via metal accumulation within temperate algal beds. The effects of storm water were monitored during a two-year survey of Sydney Harbour which sampled epifauna before and after heavy rainfall. Epifaunal assemblages declined throughout the harbour following storm events but for the most part these declines were not attributable to storm-water runoff. However, transient (&lt 4 d) and localized impacts of storm water upon physico-chemical characteristics of recipient water and some epifaunal groups were identified around storm drains. A novel field dosing technique tested the relative importance of freshwater and associated metals as causative agents of behavioural avoidance and direct mortality responses. Strong avoidance of storm-water plumes was found which could be entirely explained by freshwater inundation, with no additional effects of metals. No direct mortality was observed following brief exposures. Contaminants introduced by storm water may accumulate within the tissues of macroalgae and potentially pose persistent threats to epifauna. Colonisation of epifauna was reduced on algae with enhanced copper levels, and the nesting behaviour, feeding and survival of an abundant amphipod were all negatively affected by copper load. Subsequent field surveys identified sufficient copper, lead and zinc contamination in Sydney Harbour algal beds to pose direct toxic threats to epifauna. The abundance of herbivorous amphipods correlated negatively with the copper content of a common algal species. However, differences in metal accumulation between algal species resulted in spatially variable levels of contamination. Small-scale patchiness of contaminants within these landscapes may allow populations of mobile species to persist if contaminated hosts are avoided. In summary, epifaunal assemblages appeared resilient to storm-water pulses. Recovery of affected groups was rapid and large fluctuations in abundance appear to be part of the natural flux of epifaunal communities. In contrast, assemblages responded strongly to algal-bound contaminants and this has emerged as an important pathway of contaminant exposure and impact within algal habitats.

Pasture plants already adapted to acidic soil conditions are required as part of an integrated approach (with lime amelioration) to managing acid soils on the Tablelands of New South Wales, Australia. The objective of this thesis is to evaluate the usefulness of Austrodanthonia species for this purpose. The material evaluated in this study was collected during a previous survey of the distribution of Austrodanthonia on the Central, Southern and Monaro Tablelands of New South Wales. It was hypothesised that the genus Austrodanthonia has a wide range of tolerance to acid soils. A series of experiments that provided information on the growth and physiology of Austrodanthonia in relation to soil acidity, with a view to the identification and eventual domestication of the most promising plant material have been conducted through pot, hydroponics and field investigations. Firstly, soils were acidified or limed to obtain a range of soil pH and Al concentrations. This experiment showed that adding aluminium sulfate and calcium carbonate followed by washing excess salts with water is a simple, rapid and convenient method for adjusting soil pH for pot experiments. The pH of the amended soils remained relatively unchanged eight months after treatment. The experimental set-up also resulted in a wide range of soluble Al (2-52 mg/kg) across the soils. The relative Al-tolerance of 183 accessions from 15 Austrodanthonia species was tested in a pot experiment using a range of soil pH. Emergence, survival and growth of all accessions were drastically reduced by high soil acidity (pH 3.9, P < 0.001). About 11% of plants emerged at pH 3.9, whereas at pH 4.4 and 5.3, ~72% of plants emerged. Accessions exhibited large variation within and between species in their tolerance to soil acidity. From the species/accessions tested, 49 accessions from eight species were selected for further study (on the basis of being more acid tolerant). Hydroponic experiments conducted in the glasshouse evaluated: (i) formulation of nutrient solution with a stable pH, (ii) effectiveness of the formulation using tap water and deionised water and (iii) estimation of free ion activities of Al and Mn in the nutrient solution and their effects on Austrodanthonia growth. These experiments showed that a NO3-N/NH4-N ratio of 9:4 is the most appropriate ratio to obtain a stable pH 4.0 without affecting plant growth; that there was little difference between tap water and deionised water on the ionic effects of Al and Mn, and plant-size did not play a role on accession survival and that accessions of Austrodanthonia could grow well within a wide range of pH (3.5-5.5), Al (50-250 �M) and Mn (100-2000 �M). Growth of Austrodanthonia accessions declined under high acidity (pH < 3.5) and Al (300 �M), but tolerated high concentrations of Mn (2000 �M). Root-tips stained with hematoxylin grouped accessions in a similar way to the pot and hydroponic experiments for most of the accessions tested. The intensity of root staining with hematoxylin and the differential distribution of Al in the shoots and roots provided an indication that different tolerance mechanisms may be involved with Austrodanthonia accessions. It appears that both exclusion and internal mechanisms may operate for Al- and Mn-tolerance. A field experiment was conducted at Carcoar (33037�S, 149013�E, elevation 800 m) using gradients in soil pH and Al available on-site to grow selected accessions of Austrodanthonia. The accessions exhibited a range of responses to soil acidity. The accession responses to acidity from the pot and hydroponic experiments were similar to those obtained in the field, especially where Al was present as a low Al-challenge. Overall, this study shows that Austrodanthonia exhibits a wide range of acid tolerance between species and accessions within species. Among the species tested, A. duttoniana and A. fulva appeared to have the greatest commercial potential, because of their productivity and acid tolerance. The variability that exists in the accessions may be exploitable in breeding and selection programs for improved cultivars.

Contaminants may affect marine organisms through various pathways with impacts evident across a variety of spatial and temporal scales. Organisms may encounter short pulsed exposures which contaminate surface waters for hours to days, or more persistent but patchy contamination of benthic habitats throughout their entire life-cycle. This thesis examines the responses of epifauna associated with macroalgae to a pulsed exposure of contaminants (storm-water input) and to chronic contamination via metal accumulation within temperate algal beds. The effects of storm water were monitored during a two-year survey of Sydney Harbour which sampled epifauna before and after heavy rainfall. Epifaunal assemblages declined throughout the harbour following storm events but for the most part these declines were not attributable to storm-water runoff. However, transient (&lt 4 d) and localized impacts of storm water upon physico-chemical characteristics of recipient water and some epifaunal groups were identified around storm drains. A novel field dosing technique tested the relative importance of freshwater and associated metals as causative agents of behavioural avoidance and direct mortality responses. Strong avoidance of storm-water plumes was found which could be entirely explained by freshwater inundation, with no additional effects of metals. No direct mortality was observed following brief exposures. Contaminants introduced by storm water may accumulate within the tissues of macroalgae and potentially pose persistent threats to epifauna. Colonisation of epifauna was reduced on algae with enhanced copper levels, and the nesting behaviour, feeding and survival of an abundant amphipod were all negatively affected by copper load. Subsequent field surveys identified sufficient copper, lead and zinc contamination in Sydney Harbour algal beds to pose direct toxic threats to epifauna. The abundance of herbivorous amphipods correlated negatively with the copper content of a common algal species. However, differences in metal accumulation between algal species resulted in spatially variable levels of contamination. Small-scale patchiness of contaminants within these landscapes may allow populations of mobile species to persist if contaminated hosts are avoided. In summary, epifaunal assemblages appeared resilient to storm-water pulses. Recovery of affected groups was rapid and large fluctuations in abundance appear to be part of the natural flux of epifaunal communities. In contrast, assemblages responded strongly to algal-bound contaminants and this has emerged as an important pathway of contaminant exposure and impact within algal habitats.

Pasture plants already adapted to acidic soil conditions are required as part of an integrated approach (with lime amelioration) to managing acid soils on the Tablelands of New South Wales, Australia. The objective of this thesis is to evaluate the usefulness of Austrodanthonia species for this purpose. The material evaluated in this study was collected during a previous survey of the distribution of Austrodanthonia on the Central, Southern and Monaro Tablelands of New South Wales. It was hypothesised that the genus Austrodanthonia has a wide range of tolerance to acid soils. A series of experiments that provided information on the growth and physiology of Austrodanthonia in relation to soil acidity, with a view to the identification and eventual domestication of the most promising plant material have been conducted through pot, hydroponics and field investigations. Firstly, soils were acidified or limed to obtain a range of soil pH and Al concentrations. This experiment showed that adding aluminium sulfate and calcium carbonate followed by washing excess salts with water is a simple, rapid and convenient method for adjusting soil pH for pot experiments. The pH of the amended soils remained relatively unchanged eight months after treatment. The experimental set-up also resulted in a wide range of soluble Al (2-52 mg/kg) across the soils. The relative Al-tolerance of 183 accessions from 15 Austrodanthonia species was tested in a pot experiment using a range of soil pH. Emergence, survival and growth of all accessions were drastically reduced by high soil acidity (pH 3.9, P < 0.001). About 11% of plants emerged at pH 3.9, whereas at pH 4.4 and 5.3, ~72% of plants emerged. Accessions exhibited large variation within and between species in their tolerance to soil acidity. From the species/accessions tested, 49 accessions from eight species were selected for further study (on the basis of being more acid tolerant). Hydroponic experiments conducted in the glasshouse evaluated: (i) formulation of nutrient solution with a stable pH, (ii) effectiveness of the formulation using tap water and deionised water and (iii) estimation of free ion activities of Al and Mn in the nutrient solution and their effects on Austrodanthonia growth. These experiments showed that a NO3-N/NH4-N ratio of 9:4 is the most appropriate ratio to obtain a stable pH 4.0 without affecting plant growth; that there was little difference between tap water and deionised water on the ionic effects of Al and Mn, and plant-size did not play a role on accession survival and that accessions of Austrodanthonia could grow well within a wide range of pH (3.5-5.5), Al (50-250 �M) and Mn (100-2000 �M). Growth of Austrodanthonia accessions declined under high acidity (pH < 3.5) and Al (300 �M), but tolerated high concentrations of Mn (2000 �M). Root-tips stained with hematoxylin grouped accessions in a similar way to the pot and hydroponic experiments for most of the accessions tested. The intensity of root staining with hematoxylin and the differential distribution of Al in the shoots and roots provided an indication that different tolerance mechanisms may be involved with Austrodanthonia accessions. It appears that both exclusion and internal mechanisms may operate for Al- and Mn-tolerance. A field experiment was conducted at Carcoar (33037�S, 149013�E, elevation 800 m) using gradients in soil pH and Al available on-site to grow selected accessions of Austrodanthonia. The accessions exhibited a range of responses to soil acidity. The accession responses to acidity from the pot and hydroponic experiments were similar to those obtained in the field, especially where Al was present as a low Al-challenge. Overall, this study shows that Austrodanthonia exhibits a wide range of acid tolerance between species and accessions within species. Among the species tested, A. duttoniana and A. fulva appeared to have the greatest commercial potential, because of their productivity and acid tolerance. The variability that exists in the accessions may be exploitable in breeding and selection programs for improved cultivars.

The polyamines are a group of natural compounds which have been found in almost all living tissues. N1- and N8- acetylspermidine have been known for a considerable time as normal constituents in human urine, but their physiological role is unknown. Recent studies have indicated the presence of enzymes in the tissues capable of converting spermidine into N1-acetylspermidine and N8-acetylspermidine and other enzyme activities which catalyze deacetylation and interconversion reactions. One approach for determining physiologic activity of an endogenous compound is to observe their pharmacologic and toxicologic effects. In the present study, the LD50 for N1-acetylspermidine, N8-acetylspermidine, spermidine, spermine and putrescine, were determined by intraperitoneal injection in mice. The LD50 for N1-acetylspermidine •2HCl and N8-acetylspermidine •2HCl were 1150 and 820 mg/kg, respectively, and the respective LD50 for spermidine •3HCl, spermine n#8226;4HCl and putrescine n#8226;2HCl were 870, 370, and 1400 mg/kg. The major difference between the toxicity of N1-acetylspermidine and N8acetylspermidine and that of spermidine, spermine and putrescine appeared to be the latency period for the time of death. While N1- and N8-acetylspermidine have very rapid effects in which animals died in the first ten minutes after the injection with very few delayed deaths, the effects of spermidine, spermine and putrescine occurred over a wider range of time intervals with some deaths occurring as late as ten days after treatment The other signs of toxicity with N1acetylspermidine, N8-acetylspermidine, spermidine, spermine, and putrescine were qualitatively quite similar as each compound produced hypothermia, sedation, muscle incoordination, decreased motor activity, decreased respiration, and clonic convulsions.

Published Article / The growth of Saccharomyces cerevisiae strain W303-1A(a) was evaluated in complex and chemically defined media. The use of chemically defined medium allowed the complete utilisation of glucose within 20 h. as well as all of the produced ethanol within 45 h. Maximum specific growth rates (µmax) were increased from 0.28 h-1 to 0.42 h-1 and the volumetric rate of ethanol production increased from 0.204 g l-1 h-1 to 0.597 g l-1 h-1. However, when the ethanol concentration exceeded a threshold value of 10 g l-1, the µmax value was significantly decreased. These observations suggest that ethanol metabolism related growth experiments for the relevant strain should be carried out in chemically defined medium with ethanol concentrations below 10 g l-1.

No description available.

Semiconductor manufacturing is one of the most advancing, growing and evolving industries. The production of semiconductors presents several challenges, both technologically and environmentally. The amount and complexity of the chemical substances utilized in the manufacturing process has been growing exponentially, and new chemicals are often introduced to the process and the environment. Two steps of this process play a special important role in the introduction of new chemical and demand of natural resources: Chemical Mechanical Planarization (CMP) and Photolithography.Wastewaters from the semiconductor manufacturing are complex and have several chemicals in different concentrations. Heavy metals, acids, chelators, surfactants and other chemicals are found in semiconductor effluents. Part of the scope of this study is to evaluate and remediate wastewaters produced in semiconductor manufacturing.During the development of this project it was found that copper can be successfully removed and recovered from CMP wastewaters by the use of a sulfate reducing bioreactor and a crystallization reactor, promoting precipitation of copper sulfides on the surface of silica sand. High removal and recovery efficiencies were found as result of the study. Another finding include that citrate is a readily biodegradable compound which can be successfully utilized as electron donor for anaerobic processes such as methanogenesis and sulfate reductions. However other important chelator, like EDTA, can cause toxicity to these microorganisms and affect important biological processes. PFOS is an important chemical for the semiconductor industry; however, the physical and chemical properties make this compound persistent in the environment and bioaccumulative. New substitutes for PFOS were tested and evaluated for their environmental impact. It was found that perfluorination plays an important role in the chemical properties of PFOS and removal of this characteristic improves the environmental performance of the new substitutes. Evaluation of these new chemicals was also performed by simulation and modeling. The software utilized in this study identified properties like toxicity and octanol-water partition coefficient accurately. On the other hand biodegradability was poorly estimated and new models are suggested for evaluation of this property for compounds with characteristics similar to the ones studied here (specifically high fluorination).