Poison concerns for Inanda Dam

Published Oct 15, 2008


People living around Inanda Dam, one of Durban's main water supply dams, have been warned not to eat the dam's fish or locally grown vegetables after alarming evidence of significant mercury poisoning in the dam's food chain.

Government officials said tests on drinking water at Inanda for the past 10 years showed no level of danger for the general public and there was "no reason to panic".

Nevertheless, a new report published by the Medical Research Council has found evidence of higher-than-normal mercury levels in several people living around the dam, and 50 percent of fish samples from the dam were polluted with mercury at levels above the safe eating limits recommended by the World Health Organisation.

Acting on recommendations from the research council report, a government task team has told people not to eat fish or vegetables as a precaution, pending the results of more comprehensive studies.

This will involve taking blood samples from Inanda Dam residents and analysing soil samples from the area.

Although the source of the contamination remains unclear, the research council and other researchers have pointed to the old mercury treatment works at Thor Chemicals in Cato Ridge as one of the likely sources.

However, some government officials and researchers have noted that separate fish and vegetable samples collected far from Thor's water catchment footprint have also shown evidence of elevated mercury levels, indicating that there could be other pollution sources.

Thor, which is now known as Guernica Chemicals, could not be reached for comment last night.

Dr Timothy Fasheun, a senior official at the agriculture and environmental affairs department who is chairing the Inanda Dam mercury task team, said it was possible that soil in the area contained naturally high levels of mercury or had been polluted by previous small-scale gold-mining operations or farm chemicals.

More tests were to be conducted by researchers from the Council of Geoscience and the University of KwaZulu-Natal, and the provincial health department planned to finish collecting blood samples from people in the area in the next two weeks.

The research council report, which also involved the Council for Geoscience and London South Bank University, showed that 12 percent to 24 percent of people in three randomly selected villages near the dam, Mshazi, Nqetho and Madimeni, had hair sample mercury levels above World Health Organisation guidelines.


The samples were collected last year from 83 village residents. People in Madimeni village seemed to have the worst mercury exposure. People who ate fish or locally grown vegetables also had the highest mercury levels in their hair.

The report, published in January but not widely circulated to the public, said the findings showed "cause for concern" and warranted "urgent attention" from authorities.

"The design of the study did not permit accurate identification of the source or sources of mercury exposure in the study communities."

But, it said, it was possible mercury had accumulated in the food chain, either from the old Thor chemicals factory - where several workers died of, or became sick in the early 1990s from, mercury poisoning - or from small-scale gold-mining, or mercury in traditional muti, skin lightening creams or shampoos.

However, there was clear evidence that the food chain was contaminated.

"There is a pressing need to... conduct a comprehensive investigation of the risk and sources of mercury exposure, and concomitant health effects in affected communities."

It also recommended comprehensive surveillance and monitoring, and public education for the community, such as guidelines to restrict eating fish, vegetables and fruit.

Rico Euripidou, an epidemiologist with the Pietermaritzburg-based environmental justice group "groundWork", said the most likely source of the contamination appeared to be Thor/Guernica, which is about 20km to 35km away from Inanda Dam, or contaminated plastic water drums.

Euripidou, who has a master's degree in environmental epidemiology from the London School of Hygiene and Tropical Medicine, said some forms of mercury were able to pass through the protective placental barrier to babies, as well as the blood-to-brain barrier.

In its vapour form, mercury could also be transported over vast distances. Mercury given off from burning coal at Eskom power stations could wind up as far away as Scandinavia and the Arctic.

At least five workers died and several others were poisoned after working at the Thor plant in Cato Ridge in the early 1990s.

The mercury recovery plant at Thor was eventually shut down by the government, but several thousand tons of mercury waste is still stored in drums in a massive sealed warehouse at the site, pending a final decision on how to dispose of the poison safely.

Agriculture and environment affairs MEC Mtholephi Mthimkhulu said on Tuesday that, although an extensive study was being planned to determine the magnitude of the problem at Inanda, "we wish to call on people not to panic yet as preliminary findings clearly indicate that water is safe for human consumption".

Local community leaders had also been alerted to the potential problems, he said.

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