Pretoria - South African river water is highly contaminated with a cocktail of bacteria. This water is used to irrigate agricultural produce all over the country and, if eaten raw, the contaminated food reaches and can cause illness in consumers.
This was said on Monday by Trevor Britz, professor in food science at Stellenbosch University at a congress being held by the SA Association for Food Science and Technology at the CSIR in Pretoria.
Britz is a scientist with a DSc from Pretoria University, specialising in environmental bacteriology. With colleague C Lamprecht, he has for four years headed a team conducting a study funded by the Water Research Commission and the Department of Agriculture on the use of river water for irrigation in agriculture.
The results have shown unequivocally that the microbial levels of rivers and fresh produce monitored in South Africa are unacceptably high.
Britz told the congress that consumption of fresh produce was increasing worldwide and, since often eaten raw, it made an excellent vehicle for disease transmission. Not surprisingly, food-borne disease outbreaks linked to fresh produce are increasing in number and intensity.
Although fresh produce can become contaminated at any time in the agri-food chain, pre-harvest contamination is considered the most likely origin. One important source of pathogens found on fresh produce is from faecally-contaminated irrigation water. Over the past decade the microbial quality of many local rivers used for irrigation of fresh produce has decreased and pollution levels are far above recommended World Health Organisation and local guidelines.
In some rivers faecal indicators reached “log 7” cell concentrations. In many cases the rivers did not meet the international faecal guideline for safe irrigation with Escherichia coli concentrations exceeding 1 000 colony-forming unit (cfu) per 100 ml-1.
The presence of indicator organisms indicated unsanitary conditions, as well as the presence of potential pathogens including staphylococcus, klebsiella, listeria, salmonella, enterococcus, coliforms, E coli, norovirus and hepatitis-A viruses, and protozoa.
It was concluded that there was a high risk of exposure to human pathogens when water from these rivers is used to irrigate produce that is consumed raw.
In view of this, as well as the seriousness of recent E coli food-borne outbreaks which involved multi-drug resistant pathogenic E coli strains, it could be argued that the potential of E coli as an emerging pathogen on fresh produce poses a serious risk.
In his lecture Britz said informal settlements and industrial pollution were the main sources of river contamination. “Our findings are extremely unpopular with both central and provincial governments and municipalities.”
Intervention was required to reduce the health risks but concerns were dismissed, for instance by saying the E coli contamination was reduced by the rivers. This was found to be untrue as the contamination was often just as bad downstream.
Education of the public was paramount in terms of hygiene, like washing hands and food, he said.
From the authorities, better sewerage infrastructure was urgently required. Many settlements had sewerage and water, but the capacity was too low to handle the load.
Unless something was done, the risk would increase, he said. - Pretoria News