ABSTRACT
The aquatic environment represents almost 70% of the earth’s surface. In the past few decades, pollution in the aquatic environment has been growing at an alarming rate primarily because of the release of a large number of pollutants of anthropogenic sources. Industrial, community and agricultural effluents that are released into the aquatic environment are often comprised of a complex mixture of toxic organic pollutants.1,2 Several hundreds of such pollutants are considered to be particularly dangerous, either by themselves in isolation or in synergy with others. Some have been the subject of numerous studies, but there are other biological impacts which are virtually unknown. Polyaromatic hydrocarbons (PAH), chlorobenzenes, polychlorinated biphenyls (PCB), polychlorinated-dibenzo-furans-and -p-dioxins (PCDF/ PCDD), and chlorinated phenols are some of the vital hazardous and most studied potential carcinogenic organic pollutants of the aquatic environment.3-6
The detection of low-level chemical pollutants such as PCB, PAH, and organochlorides by chemical methods are expensive and require extensive instrumentation and skilled personnel. Biological risk of the pollutants cannot be evaluated by this type of approach6-9. Thus, there is a need for sensitive biological indicators to be used for biological risk assessment of polluted sites. Biological indicators may be defined as the biochemical, physiological, and histological changes in biological samples; or as an irregularity in whole organism or community that may be to estimate direct or indirect impact of a pollutant.6-8 Prior to perceiving the biological responses incited by pollutants in aquatic organisms it is important to understand transport, degree of bioavailability and uptake of the pollutants by exposed organisms.3,5
7.2 TRANSPORT, BIOAVAILABILITY AND UPTAKE
Pollutants are transported to and distributed across media (eg water and sediment) and biota through a number of physical, chemical and biological processes. Chemical transportation in the aquatic environment may take place:
(i) From atmosphere to water; (ii) From water to sediment and organisms; and
(iii) Within water bodies.10
