Food warning due to heavy metals in Mngeni River

A study has found that the long-term use of water from the Mngeni River for irrigation could be a health hazard because of contamination by heavy metals.

A study has found that the long-term use of water from the Mngeni River for irrigation could be a health hazard because of contamination by heavy metals.

Published Mar 18, 2023


Durban - Water from the Mngeni River, used for irrigation and the main source of water Durban, is contaminated with heavy metals.

A study by the deputy director at the Technology Station in Chemicals at MUT, S’busiso Nkosi and Nomaxhosa Msimango, a control technician at MUT’s Department of Chemistry, published their findings in the South African Journal of Science.

The study was conducted on a local farm, the Fair Food Company and Edamame Development Programme in Pinetown.

It found that human well-being and ecological reliability faced a major threat from heavy metal pollution to soils caused by untreated discharge from metropolitan and industrial wastewater.

The researchers cautioned against the long-term reuse of irrigated water with hazardous metals because it causes an excessive build-up of the metals in soil and crops.

While the study found heavy metals to be within the global limit for agricultural use in the sampled plants (lettuce and Chinese Cabbage), it found that water from the nearby river, which is used for irrigation, was contaminated with heavy metals.

“The content levels of Cu (copper) and Fe (iron) in water were measured to be 0.075 mg/kg and 0.731 mg/kg respectively, which exceeds the WHO (World Health Organisation)/FAO (Food and Agriculture Organisation of the United Nations) standard parameters of 0.017mg/kg and 0.50mg/kg, respectively,” the study found.

“The findings suggest and indicate that waste management and healthy environmental practices in the study area around the Mngeni River are critical to ensure that the river is not contaminated with heavy metals. It further recommends that to keep the environment less affected by heavy metals, proactive health agencies, trash disposal knowledge, and best practices should be maintained,” said Nkosi.

He also said people should minimise polluting the environment with proper waste management and the government should put more emphasis on food security initiatives.

“Consumption of high levels of copper can cause nausea, vomiting, diarrhoea, gastric complaints and headaches. Long-term exposure over many months and years can cause liver damage and death. Zinc is considered a fundamental component of human existence; however, acute and chronic exposure to excessively high concentrations of zinc can cause nausea, vomiting, diarrhoea, fever and lethargy. Excess iron in the system can cause cirrhosis when deposited in the pancreas, liver cancer when deposited in the liver and cardiac arrhythmia when deposited in the heart,” the study cautioned.

The Duzi-Mngeni Conservation Trust (Duct), a non-profit public benefit organisation championing the environmental health of the Msunduzi and Mngeni Rivers, concurred with the study, saying weekly water quality tests showed that the Mngeni River was heavily contaminated not only by the heavy metals but also solid waste.

Duct pollution control officer Sanele Vilakazi said pollution in the Mngeni River posed a great threat to people.

“I know for a fact that Mngeni is polluted, and the main factor is littering. At Duct, we conduct awareness campaigns to warn people about littering the river. Figures show that pollution at the Mngeni River gets worse each year, and if people do not take care of such an important river, we may have a problem in future,” Vilakazi warned.

Janet Simpkins from Adopt a River KwaZulu-Natal said when they tested the Mngeni River water samples, they only did it for E. Coli and had never tested for heavy metals.

“That kind of testing is expensive, but I can say that it is difficult to notice that water is contaminated without testing it. Our water sampling over the year shows that the river is highly contaminated with E. coli, and if other studies come up and show that it is also contaminated because of heavy metals, then it is very dangerous and should be attended to urgently,” said Simpkins.

Nkosi said a more detailed study for the analysis of wider range of heavy metals was the next phase of the project.

The Independent on Saturday