Xenobiotics environmental behaviour

The environmental behaviour of LAS, as one of the most widely-used xenobiotic organic compounds, has aroused considerable interest and study. As a result, it has been determined that, under certain conditions, LAS compounds are completely biodegradable however, in the marine environment their degradation is known to be slower. The presence of metabolites of the anionic LAS surfactants, the long and short chain SPC derivatives, in the aqueous environment is well known, and as such these degradation intermediates needed to be monitored (and tested for their toxic effects). 

Human exposure to environmental contaminants has been investigated through the analysis of adipose tissue, breast milk, blood and the monitoring of faecal and urinary excretion levels. However, while levels of persistent contaminants in human milk, for example, are extensively monitored, very little is known about foetal exposure to xenobiotics because the concentrations of persistent compounds in blood and trans-placental transmission are less well studied. Also, more information is needed in general about the behaviour of endocrine disruptive compounds (and their metabolites) in vivo, for example the way they bind to blood plasma proteins. 

Although the globally distributed DDT is a very well investigated xenobiotic regarding the environmental occurrence and behaviour, detailed information about the fate of DDT in the bound residues fraction is very limited. Already in 1977 Lichtenstein et al. (1977) reported the formation of bound 14C-labelled DDT on agricultural soil accompanied by a drastically reduced insecticidal activity of the associated proportion. Also recent studies confirmed the decrease of DDT toxicity with time after application to soils as a result of less bioavailibility due the incorporation into the non-extractable particulate matter (Robertson and Alexander 1998). For a better understanding of the processes leading to these observations more information is required about the incorporation of DDT residues into the non-extractable particulate matter not only of soils but also of particulate matter within the aquatic environment. 

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