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Risk Characterisation
All the information concerning the hazard identification, dose-response assessment,
and exposure assessment are used to characterise and describe the extent of the
overall individual or population risk. The most significant quantitative and qualitative
aspects of these assessments, the assumptions used and the identified uncertainties
are assessed, summarised and discussed to provide an overall estimate of individual
risk. If information and data are available this can also be expanded to estimate
overall population risk. Guidance on the risk characterisation process and examples
of how to compile these documents can be found in the USEPA publications (USEPA
1997; du Preez et al., 2003a). To perform these risk calculations for the chemical
contaminants found in freshwater fish from South African systems and for different
scenarios the Risk*AssistantTM software package can be used.
DISCUSSION
The method suggested in this paper has been tested on rivers and impoundments
in South Africa (Heath 1999, du Preez et al., 2003b) and the data indicate that there
are potential metal and biocide health risks associated with the daily consumption of
fish. The method has been further developed and tested by the regulatory authority in
South Africa and published as a series of reports by the Water Research Commission
(Heath et al., 2004a,b).
It is important to note that due to the differences in fish species, fish sizes and
cultural beliefs freshwater fish are prepared and eaten in different manners in South
Africa, ranging from filleting of larger fish to smaller fish being cooked whole. The
consumers of these fish must be aware that certain tissues (such as liver, skin, testes
and eggs) can have high levels of contamination, which could result in a human
health risk (Heath et al., 2004b).
The different levels of assessment proposed in this method will also enable an
accurate assessment of diffuse pollution run-off from mines dumps, mine water
decants (heavy metals) and agricultural run-off (mainly biocides). There is an
international move, with the Stockholm Convention on Persistent Organic Pesticides
(POP’s) as one of the driving forces, for aquatic biota to be monitored for levels
of POP’s (DWAF, 2006). The protocol proposed in this paper will be ideal for such
surveys. There is trend in America and Europe towards Total Maximum Daily Loads
(TMDL), or the amount of pollution that a water body can receive and still meet water
quality objective. The water quality objective includes the aquatic life requirements.
The methodology developed can be used as a check to determine if the fish are in
fact healthy and able to reproduce in a sustainable manner as well as to ascertain if
humans can in fact consume the fish without ill effects.
The methodology should provide guidance to governmental authorities at national
or provincial level and project managers for the collection of data and information
as well as for the assessment, management and communication of the health risks
associated with the consumption of freshwater fish. The basic requirements are
highlighted, as limited resources (financial, infrastructure and skilled personnel)
in South Africa would curtail the possibility of undertaking detailed assessments
as undertaken by the United States of America Environmental Protection Agency
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