ENVIRONMENTAL REMEDIATION Subject

Figures for environmental expenditure are provided in the annual report. In 1999 PPG had cash outlays of US 22 million and charges against income of US 10 million in relation to environmental remediation. It also had reserves for environmental contingencies of US 82 million, although it is stated the Company may be subject to loss contingencies related to environmental matters estimated to be as much as 200 million to 400 million .

The IWA (International Water Association), formerly known as the IWQA, has had several task forces working on model development for various types of processes. I believe that these reactor models have a good potential application for remedial treatment. The subject of the models is extremely complex and too involved for this discussion, as it is a Master s Level course in Environmental Engineering. However, let me indicate that there are several types of models which may have some application to the bioremediation field. The principal models are... 

Environmental samples often contain swathes of different chemicals in mixtures. An important question for risk assessment, regulation, and remediation is to establish whether the majority of chemicals contribute to the overall mixture effect, or whether joint toxicity can be traced back to a few substances. This issue has been the topic of considerable research efforts in the field of ecotoxicology. Its resolution has required whole mixture approaches, where environmental samples were subjected to extraction procedures, followed by fractionation and chemical analysis (toxicity identification evaluation (TIE), bioassay-directed fractionations). There are interesting examples in the literature where such approaches were combined with component-based mixture assessments with the aim of identifying chemicals that contribute to mixture effects (see Chapter 4). 

The importance of redox effects on coupled iron-phosphorus cycling in freshwater systems has been the subject of study in applied environmental science, where phosphate removal from eutrophic natural waters and wastewaters, by sorption onto Fe-oxyhydroxide phases, has been explored as a remediation measure. Phosphate also has a pronounced tendency to sorb onto Al-oxyhydroxides, and these phases have been used in remediation of phosphate overenriched aquatic systems, as well (e.g., Leckie and Stumm, 1970). 

The previous sections of this chapter have briefly described the nature and locations of the most serious radioactive environmental contamination on the planet and have established the geochemical foundations for understanding the behavior of radionuclides in the environment. Applications of this information to remediating or assessing the risk posed by the contamination is the subject of this section of the review. 

It is possible that high rates of self-reported symptoms may be due to stress or greater symptom recall. For example, there are reports that elevated symptom reporting rates have continued despite interim remediation or closures of the landfill sites. It is often not clear whether subjective symptoms are the result of a direct toxicological effect, stress, such as environmental or odour worry, or increased symptom perception and recall. 

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