Abstract
The degradation of freshwater aquatic ecosystems is a problem occurring in
countries throughout the world. This degradation can be attributed to the input of
human waste products and wastewater resulting from agricultural and mining
practices. Since South Africa is classified as a 3rd world country, the development
and growth in the industrial and agricultural sectors far outweigh any remediation
taking place in response to existing environmental damage. Understanding the
effects of xenobiotics and pollutants on aquatic systems is an important step in
improving the management of impacted areas.
Many pesticides are characteristically lipophilic, allowing them to accumulate within
organisms occupying freshwater and marine systems. The organisms living within
affected systems may bio-accumulate pesticides, such as 1,1'-(2,2,2-trichloro-1,1-
ethanediyl)bis(4-chlorobenzene) (4,4’-DDT) directly through the water. Bioconcentration
within fish may take place through the food chain, since many species
have both plant and animal based diets, resulting in the addition of 4.4’-DDT from
various levels within the same food chain. The manufacture and large scale use of
4,4’-DDT began in 1939 and ended when it was banned by the United States
Environmental Protection Agency (USEPA) in 1972. This 33 year time period
resulted in massive inputs of 4,4’-DDT into the natural environment. Concentrations
of 4,4’-DDT are still present in areas including Europe and the United States of
America where 4,4’-DDT is no longer applied in any way, shape, or form.
The current use of 4,4’-DDT in approximately 43 African countries only occurs under
special dispensation from the World Health Organisation (WHO) for the control of the
Anopheles sp. mosquito. This genus of mosquito is the vector for malaria, a parasitic
blood infection which caused the death of 445 000 people in Africa in 2016. Current
application of 4,4’-DDT in areas most affected by malaria takes place through indoor
residual spraying (IRS) of houses and homesteads. The potential for 4,4’-DDT to
enter surrounding aquatic systems through spray drift during IRS or runoff caused by
rain following IRS is extremely high. The lipophilic nature of 4,4’-DDT and the fact
that it has been established as a known endocrine disrupting chemical (EDC), makes
understanding the immediate effects that 4,4’-DDT may have on aquatic biota in
areas where its use is still common practice, very important...
Ph.D. (Zoology)