Environmentally relevant studies

Although Zika and co-workers (36) investigated the direct photoreaction of methyl iodide, there are few other environmentally relevant studies of direct photoreactions of saturated halocarbons in water. Kropp (37), however, re-... 

Photodegradation [182] and microwave thermolysis [183] of pollutants, toxic agents or pathogens in waste water, often in combination with a solid catalyst (e.g., Ti02), are two important methods for their removal. Results from environmentally relevant studies of the combined use of MW and UV [97, 101-103] have already appeared in the scientific literature and the topic is also covered by several... 

The acute toxicity of chlorinated paraffins to mammals, binds, and fish is very low (8), but over longer periods of exposure certain chlorinated paraffins have proved to be toxic to some aquatic species. However, the very low water solubility of chlorinated paraffins has made studies on aquatic species complicated. Laboratory experiments in which the chlorinated paraffins had been artificially solubilized showed only the short-chain grades to be toxic at low concentration other longer-chain grades showed no adverse effects on the majority of aquatic species tested. The degree of solubilization achieved in the laboratory is unlikely ever to be experienced in the environment and is of doubtful environmental relevance (9). 

Edgren carried out a number of studies in which bioassays were used to compare the widely differing potencies of a number of analogues of 17/i-oestradiol that were modified in the 18-position. Commenting on the use of potency ratios, Edgren concluded that they were only valid for specific substances and test systems and useless for product safety testing . These problems could have important consequences for any attempt to establish the potency of specific environmental EDs or environmentally relevant mixtures. 

Studies of the effects of in vitro exposure to a range of concentrations (encompassing environmentally relevant concentrations of monobutyltin, dibutyltin, and tributyltin) on human natural killer lymphocytes obtained from adult male and female donors revealed the presence of detectable concentrations of the butyltins in all the donors, indicating possible exposure of natural killer cells to butyltins in the blood. It was suggested that the study provided evidence that butyltin compounds significantly inhibit natural killer cell function and possible natural killer cell-mediated potential in humans (Whalen etal, 1999). 

The mink Mustela vision) is a piscivorous mammal that also has been exposed to relatively high dietary levels of methyl mercury in North America in recent times. In a Canadian study, mink trapped in Yukon territory, Ontario, and Nova Scotia were analyzed for levels of mercury and abundance of muscarinic, cholinergic and dopaminergic receptors in the brain (Basu et al. 2005). A correlation was found between total Hg levels and abundance of muscarinic receptors, but a negative correlation was found between total Hg and abundance of dopaminergic receptors. Thus, it was suggested that environmentally relevant concentrations of Hg (much of it in methyl form) may alter neurochemical function. The highest levels of mercury contamination were found in mink from Nova Scotia that had a mean concentration of total Hg of 5.7 pg/g in brain, 90% of which was methyl mercury. 

More controversially, endocrine disruption as a consequence of exposure to the herbicide atrazine (2-chloro-4-ethylamine-6-isopropylamine-s-triazine), one of the most widely used herbicides in the world, has also been hypothesized to explain various adverse biological effects in frog populations in the United States. Exposure to atrazine in the laboratory at high concentrations, far exceeding those found in the natural environment, has been reported to induce external deformities in the anuran species Rana pipiens, Rana sylvatica, and Bufo americanus (Allran and Karasov 2001). Studies by Hayes et al. have suggested that atrazine can induce hermaphroditism in amphibians at environmentally relevant concentrations (Hayes et al. 2002 Hayes et al. 2003). Laboratory studies with atrazine also indicated the herbicide... 

The effects of EDCs on behavior in fish have been more extensively studied than in birds. Examples of the effects of EDCs seen in fish include profound alterations in courtship behavior in male guppies (Poecilia reticulate) exposed to vinclozolin and DDE, including at environmentally relevant concentrations (Baatrup and Junge 2001) and altered courtship behavior in three-spined stickleback exposed to environmentally relevant concentrations of EE2 (Bell 2001). In the stickleback studies, exposed males became less aggressive and had a reduced nesting activity, and this was linked with reduced concentrations of the male sex androgen 11-ketotestosterone. Recently,... 

An appropriate mineral medium supplemented with the organic compound that is to be studied is inoculated with a sample of water, soil, or sediment. In studies of the environmental fate of a xenobiotic in a specific ecosystem, samples are generally taken from the area putatively contaminated with the given compound so that a degree of environmental relevance is automatically incorporated. Attention has, in addition been directed to pristine environments, and the issues of adaptation or preexposure have already been discussed. 

Laboratory experiments using natural consortia under defined conditions have particular value from several points of view. They are of direct environmental relevance, and their use minimizes the ambiguities in extrapolation from the results of studies with pure cultures. They provide valuable verification of the results of studies with pure cultures and make it possible to evaluate the extent to which the results of such studies may justifiably be extended to the natural environment. It should be appreciated, however, that in some cases the habitats from which the inoculum was taken might already have been exposed to xenobiotics so that natural enrichment (preexposure) could already have taken place. This has been discussed in Chapter 4. 

Sublethal effects in birds are similar to those in other species and include growth retardation, anemia, renal effects, and testicular damage (Hammons et al. 1978 Di Giulio et al. 1984 Blus et al. 1993). However, harmful damage effects were observed at higher concentrations when compared to aquatic biota. For example, Japanese quail (Coturnix japonica) fed 75 mg Cd/kg diet developed bone marrow hypoplasia, anemia, and hypertrophy of both heart ventricles at 6 weeks (Richardson et al. 1974). In zinc-deficient diets, effects were especially pronounced and included all of the signs mentioned plus testicular hypoplasia. A similar pattern was evident in cadmium-stressed quail on an iron-deficient diet. In all tests, 1% ascorbic acid in the diet prevented cadmium-induced effects in Japanese quail (Richardson et al. 1974). In studies with Japanese quail at environmentally relevant concentrations of 10 pg Cd/kg B W daily (for 4 days, administered per os), absorbed cadmium was transported in blood in a form that enhanced deposition in the kidney less than 0.7% of the total administered dose was recovered from liver plus kidneys plus duodenum (Scheuhammer 1988). 

In this case, the mineralogical studies on the mechanism of sulfide alteration and on the genesis and evolution of secondary oxidation products are of paramount environmental relevance because they allow a better understanding of the source and the mechanisms of release of the ecotoxic elements and the effective... 

To date, there have been only very few studies on the sorption of environmentally relevant HIOCs to membranes. In contrast, there exists a large body of literature on ionogenic drug partitioning (see, e.g. [3-5]), and the partitioning of hydrophobic ions [6], and the use of fluorescent membrane probes [7], This literature review attempts to relate the findings from these related scientific fields to environmental chemistry. 

In the simplest case of a competitive uptake of two metals (or a metal and proton) for an identical uptake site under equilibrium conditions, the reduction of the uptake flux of the solute can be quantitatively predicted using the respective equilibrium formation constants (equations (38) (41)). As can be seen in Table 3, for a given study, constants among the trace metals, protons and alkaline earth metals are often sufficiently similar for competition to be important. Nevertheless, competition is likely to be negligible under most environmentally relevant conditions where competition occurs between low concentrations of metals, such that the free carrier concentration remains approximately equal to the total receptor concentration. 

From the available literature it becomes clear that method evaluation studies do not surpass the level of within-laboratory performances. Although several of these (see Table 3.3.1) reveal satisfactory levels of quality and environmentally relevant limits of detection, a genuine quality assurance of these methods is still lacking. There are no reports of interlaboratory studies and certified reference materials for surfactants are not available on the market yet. It can therefore be concluded that there remains much to be done in the field of improving and evaluating quality of analytical measurements of surfactants in biota. 

The reversibility of sorption has considerable environmental relevance, because it permits the recovery of ecosystems after exposure to contamination, and makes possible the re-dissolution of chemicals that have been sorbed onto particulate material. For this reason, this aspect has been studied extensively, with results showing that sorption onto natural sediments is a reversible process for non-ionic [17] and anionic surfactants [8,20,30,45,46]. This desorption process, however, has not been confirmed by other authors [3,14]. 

Legator MS, Ward JB Jr. 1984. Genetic toxicity Relevant studies with animals ahd humans. In Reproduction lie new frontier in occupational and environmental health research. Prog Clin Biol Res 160 491-525. 

Fig. 6. Average concentrations of several potentially toxic and environmentally relevant metals in the different types of HT materials studied.

Chemical (abiotic) hydrolysis has been well studied by organic chemists for many years, frequently under environmentally relevant conditions (in water at ambient temperature and pH 5-9) [25]. Testing is sometimes carried out at elevated... 

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