The mismanagement of Lake Chivero, Harare’s primary water source, is endangering the lives of millions, according to new research which reveals that the lake’s water now poses cancer risks up to 15 times greater than those associated with HIV.
Years of unregulated discharge of untreated sewage, industrial waste, and agricultural runoff have transformed the lake into a hazardous chemical mix.
In December 2024, the government imposed a fishing ban on Lake Chivero following the unexplained deaths of four white rhinos, three zebras, several wildebeests, and large numbers of fish, believed to have consumed contaminated water from the lake.
Professor Hilda Matarira, a Chemical Pathologist at the National Health Laboratories and Parirenyatwa Hospital, under the University of Zimbabwe’s College of Health Sciences, has been monitoring the water quality of Lake Chivero for nearly 25 years. She said:
We have researched water quality in Lake Chivero since 2000—nearly 25 years ago. The lake’s contamination is rising each year.
Microcystins from blue-green algae are cancer-causing and kill people at rates 15 times higher than HIV.
This algae chokes the lake of oxygen, leading to the death of fish and other aquatic organisms. Lake Chivero is a crucial water source for Harare, Chitungwiza, and Ruwa.
Microcystins are a class of toxins produced by certain cyanobacteria, commonly known as blue-green algae.
These toxins are cyclic peptides that can be highly toxic to humans and animals, primarily affecting the liver.
Exposure to microcystins can occur through ingestion of contaminated water, consumption of affected fish or shellfish, or direct contact during recreational activities like swimming.
Professor Matarira further warned that relying on borehole water, often considered a safer alternative, may not provide a viable solution. She said:
We found 100% E. coli contamination in some boreholes. Heavy metals and nitrates from the lake are serious concerns.
Boiling water only kills bacteria—it does nothing for heavy metals. Recent studies show that late rains may wash more chemicals into groundwater.
However, her most serious warning relates to the consumption of fish—a key source of livelihood for many communities living around Lake Chivero. She said:
The worst thing about these particles, besides their consequences in the water, is that while you are unaware, the particles pierce everything—every organ in a human being, animal, whatever.
They are one of the major causes of cancer. Some families and even pets are being affected by this pollution.
High mercury levels are present in the fish, and unsuspecting consumers are at risk of heavy metal poisoning.
