Eat lettuce and cabbage, but worry about the irrigation water – MUT study finds

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1 March 2023


Eat lettuce and cabbage, but worry about the irrigation water – MUT study finds

A study by Mangosuthu University of Technology (MUT) 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.

Co-authored by S’busiso Nkosi, a Deputy Director at the Technology Station in Chemicals at MUT, and Nomaxhosa Msimango, a Control Technician at MUT’s Department of Chemistry, the study was published in the South African Journal of Science. It was titled, ‘Screening of zinc, copper and iron in lettuce and Chinese cabbage cultivated in Durban, South Africa, towards human risk assessment’.

While the study found heavy metals to be within 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 0.017 mg/kg and 0.50 mg/kg, respectively,” the study found.

The study was conducted at The Fair Food Company & Adamame Development Programme in Pinetown, KwaZulu-Natal, South Africa. The irrigation water used in this agricultural site was collected from Umgeni River.

“Consumption of high levels of copper can cause nausea, vomiting, diarrhea, gastric (stomach) complaints and headaches. Long-term exposure over many months and years can cause liver damage and death. Zinc is considered a fundamental component for 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 arrythmia when deposited in the heart,” the study warns.

The study findings indicate that waste management and healthy environmental practices in the areas surrounding the Umgeni River are critical to ensuring that the river is not contaminated with heavy metals.

“It is recommended that, to keep the environment less affected by heavy metals, proactive health agencies, trash disposal knowledge, and best practices should be maintained,” the study recommended.


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