‘Swimmers at risk on polluted city beaches’
SWIMMERS using polluted Cape Town beaches faced significant health risks, a top scientist has warned.
The City of Cape Town had underestimated the risks posed by polluted seawater on the Atlantic and False Bay coastlines, epidemiologist Dr Jo Barnes cautioned.
A report by the city on the state of beaches and bathing spots over the 12 months which ended in June identified several places which failed to comply with health and safety regulations “by a very small margin” but were generally deemed still safe for swimming this summer.
Samples indicated pollution contamination along the False Bay coastline at Muizenberg, near the train station, and six spots from Macassar to Strand.
Sites that were not up to scratch on the Atlantic Seaboard were Melkbosstrand, Blouberg Big Bay, Three Anchor Bay, Rocklands, Saunders Rock and The Kom, opposite Harmony Park.
Brett Herron, mayoral committee member for transport, said the margin of non-compliance was very small and the beaches were safe for swim- ming, unless otherwise indicated by the city’s health department.
However, Barnes believes the data is difficult to interpret as it has been “smoothed” to present averages. This might paint a more rosy picture than merited and the findings should be handled with caution.
“These sites did not comply by a very small margin, which indicates the pollution levels were relatively low. Sites that are chronically noncompliant, and which exceed the guidelines by a significant margin, are probably affected by severe pollution which may be ongoing and would, therefore, be more risky,” Herron said.
“Some sites, however, may fail guidelines by a small margin and this could be due to sporadic low levels of pollution.
“As such, these sites have a lower risk level.
“The health department assesses these figures and will issue an advisory and or erect appropriate signage at contaminated sites.
“With regard to swimming at the beaches, it would only be advisable to avoid swimming if these signs are displayed,” he said.
“Typically, the amount of pollution is measured by how much e coli ( Escherichia coli) bacteria are present in every 100ml of water. However, the report does not indicate which organism is used in which tables.
“When the city indicates that an area is non-compliant, it simply states that it is over the limit but not by how much. In reality, the higher the level, the greater the health risk. Not reporting on peak pollution periods makes it difficult to interpret the real health risks.”
“The pollution data are often averaged or ‘smoothed’, thereby removing the peak data values. The health risks are particularly high at peak values, which are not listed.
“Some of these sites are monitored only a few times a year. That means that there are large periods for some of the sites that there is no knowledge of the peaks in pollution levels that may have occurred unnoticed or undetected,” Barnes said.
Professor Tally Palmer, director of the Unilever Centre of Water Quality Institute for Water Research at Rhodes University, agreed that some aspects highlighted by the city’s report needed to be tackled, notably those linked to spills from waste water treatment works (WWTW).
“The report states that there are 110 pump station and rising sewage overflow incidents over the time period of the report. This report may not have staffing implications for the city but it sure does for WWTWs.
“This needs to be highlighted as there is a dependency on better WWTW function with success. The issue of illegal dumping should also be addressed,” Palmer said.
According to the report, the recently completed upgrade at the Phoenix pump station would help deal with overflow.
Earlier this month, the collapse of a major pipe caused a sewage spill into Milnerton Lagoon. A high e coli concentration led to the public being warned to stay out of the water.
The sewage spill is reportedly being treated with a mixture of enzymes and several bacteria.