Online Reporter
Johnson Siamachira, Correspondent
FIVE decades after Zimbabwe defied the West’s ban on the pesticide Dichlorodiphenyltrichloroethane — commonly known as DDT — the harmful consequences of its use are becoming alarmingly evident in the Zambezi Valley’s delicate ecosystem.
Perhaps most disturbing is the recent discovery of DDT traces in the breast milk of women living in Nyamhunga, a high-density suburb in Kariba, a town on the shores of Lake Kariba. Despite the pesticide’s well-documented toxicity and widespread bans across the globe, Zimbabwe continued to use DDT for controlling tsetse flies and mosquitoes, citing its affordability and effectiveness.
However, the long-term environmental and health costs may have far outweighed the short-term benefits. Zimbabwe only officially banned the use of DDT in 2001.
DDT, which disrupts the nervous system of animals and leads to death, was banned in many countries due to its cumulative and adverse effects, including significant biodiversity loss and, in some cases, the complete disappearance of species. Despite repeated warnings, Zimbabwe persisted in using the chemical, prioritising its cost-effectiveness in pest control.
Medical officials at Kariba District Hospital have since launched studies to assess the impact of DDT on human health.
“We analyse pesticide residues in human tissue through autopsies or biopsies, but using breast milk is a convenient alternative. While the results are not conclusive, we are conducting further investigations into DDT levels,” said one official.
In the Zambezi Valley, both ecological and chemical methods have been used to control fly populations. Ecological strategies include clearing riverine vegetation and eliminating wild animals that serve as food sources for tsetse flies.
On the chemical front, chlorinated hydrocarbons such as DDT have been used since 1967 by the Tsetse and Trypanosomiasis Control Branch in the Ministry of Lands, Agriculture, Fisheries, Water and Rural Development, and by the Ministry of Health and Child Care for malaria control since 1972.
Between 1978 and 1989, DDT applications for tsetse control averaged 200 tonnes annually, peaking at 442 tonnes in 1986. From 1968 to 1979, more than 36 000 square kilometres were treated with DDT, followed by an additional 32 550 square kilometres from 1979 to 1990.
These figures highlight the extensive use of DDT, particularly in the Zambezi Valley, where some areas were treated up to 13 times.
The Blair Research Laboratory under the Ministry of Health and Child Care has confirmed the availability of alternatives to DDT.
“While alternative chemicals exist, it is premature to determine their long-term effectiveness due to developing pest resistance,” an official noted.
The impact of DDT extends well beyond human health. Dr Lightone Marufu, an aquatic ecologist in the Biological Sciences Department at the University of Zimbabwe and representative at the university’s Lake Kariba Research Station, emphasised the pesticide’s harmful effects on local wildlife.
“DDT can cause thinning of eggshells in birds of prey and crocodiles, possibly leading to reproductive failures and, consequently, biodiversity losses,” Dr Marufu said.
Studies on the African Goshawk have shown a significant population decline, likely linked to DDT spraying for tsetse fly control. Fish populations in Lake Kariba have also suffered, with elevated DDT residues found in fish from treated areas.
“DDT affects sex hormones, leading to imbalances in wildlife,” Dr Marufu said.
A study by two ecologists from the Zimbabwe Parks and Wildlife Management Authority revealed that out of 22 woodland bird species, eight were significantly less abundant in areas treated with DDT. This decline underscores the broader ecological consequences of persistent pesticide use.
Although DDT has been banned in Zimbabwe since 2001 for agricultural purposes, it is still permitted for certain public health uses, particularly in malaria vector control. The country’s regulations reflect an attempt to balance health needs with environmental concerns.
In Zimbabwe, the legacy of DDT highlights a complex struggle between public health priorities and environmental sustainability. The Zambezi Valley, a vital ecosystem supporting diverse wildlife and local communities, now faces an uncertain future as ecological degradation continues to unfold.
Dr Marufu stressed the importance of exploring bioremediation to remove or reduce DDT from the environment.
“There is a great need to use environmentally friendly control methods against pests,” he said.
“But this will require partnership and co-operation, among relevant stakeholders. Policymakers should be encouraged to consider both human and ecosystem health in the short and long term.”
As the nation grapples with these challenges, the question remains: was the continued use of DDT worth the cost to health and biodiversity?
Without urgent action to reassess pest control strategies, Zimbabwe risks not only the health of its people but also the integrity of its natural environment.
New Ziana.
