Southern African Center for Cooperation in Agriculrural and Natural Resources Research and Training
Centro de cooperacao para investigacao, agraria, recursos naturais e formacao na Africa Austral

No. 38 June 1997

Harmise pesticide use with ecosystems: Environmentalists

Asouthern Africa continues to use some banned pesticides in attempts to provide abundant agricultural products and effective disease control, environmentalists are calling for harmonisation of pesticide use with the environment.

A report by environmentalists from the Swedish University of Agricultural Sciences International Rural Development Centre reveals that pesticides constitute the main method of pest control in the SADC region. Estimates indicate that the countries in the region import hundreds of millions of dollars worth of pesticides annually and this amont will grow at an annual rate of up to 10 percent ver the next decade. But most of these pesticides have been banned in most developed countries.

"Despite this potential increase there has only been limited progress in the development of adequate pesticide control measures to ensure safe and efficient use. This has led to the widespread occurrence of unacceptable practices with regard to the distribution and use of pesticides, posing a serious threat to human health and the environment," says the report.

In her book Silent Spring, environmentalist Rachel Carson noted that synthetic chemicals were being released into the environment "with little or no advance investigation of their effects on soil, water, wildlife and man himself". Most of these chemical pesticides called the "dirty dozen" have been banned in most countries around the globe.

The dirty dozen chemicals, dubbed so because of their harmful effects on the environment and human health, include by-products created in the manufacture, use and combustion of chlorine containing chemicals such as PVC, solvents and pesticides which include the common DDT.

Scientists have asserted that the chemicals designed most specifically to protect human health by killing pests that would otherwise poison food--end up accumulating in people, who are vulnerable to long term exposure whereas the rapidly reproducing pests mutate fast enought to develop resistance. ‘These pesticides can cause great changes in the ecosystem, for example the destruction of one part of the food chain can alter the whole system," says the book.

More so, "children are more susceptible to low levels of chemicals because they are still developing and have weaker immune systems, or because they play outside more or eat more dirt than the average adult," says Jennifer D. Mitchell in the environmental magazine, World Watch.

Most of these chemicals, also known as persistent organic pollutants, have been known to cause cancer, birth defects, infertility, under-development of sex organs and mental disorders in children as well as decreasing resistance to diseases by suppressing the immune system.

Nonetheless, most governments in the region still lack the capability to control the importation, distribution and use of pesticides as they do not have in place appropriate legislation, effective registration schemes, and the institutional infrastructure that is necessary for its enforcement.

In Zimbabwe it is forbidden to use persistent organochorides and DDT in agriculture but DDT can be used for malaria and tsetse fly control. Various press reports have revealed that traces of DDT have been found in the breast milk of women living in the tsetse infested Zambezi valley.

According to a recent state of the Environment Report for Zambia, careless use of pesticides in crop protection in the country has caused increasing concentrations of pesticide residues in consumed milk. These environmentally persistent chlorinated pesticides are showing very high concentrations in fish eagles in Lake Kariba. In Tanzania, the spraying of DDT to eliminate mosquitoes is still practised in coastal areas including Dar es Salaam, Zanzibar and Tanga.

Environmental experts have expressed concern that some of the common chemicals now readily available in homes and workplaces, in food and water, and cleaning fluids, may be undermining human as well as ecological health.

"While pesticides are designed to be usefully lethal, many however are not meant to have toxic effects on certain living creatures, yet turn out to be both highly toxic and pervasive, "says Mitchell. It has been estimated that a mother's exposure to some persistent chemicals will still be detectable five generations down the line.

In Botswana's tsetse-infested Okavango delta, an attempt has been made to eliminate the tsetse fly by aerial spraying with lethal insecticides. Endosulphan, known for its toxicity to fish, is used to eradicate tsetse flies. According to the book, Water in Southern Africa, published by SADC, IUCN and SARDC, the effects of pesticide pollution on aquatic life in Mozambique have resulted in fish deaths in the Limpopo river after aerial spraying with parathion, an organophosphorus insecticide. However, aerial spraying has been improved in an attempt to minimise environmental side-effects.

The Swedish University report recommends that countries should cooperate in pesticide management within the framework of a sub-regional network to necessitate simple exchange of information and experience and the adoptio of joint policies and common measures such as harmonisation of pesticide registration control and training. ,p> The International Forum on Chemical Safety (IFCS), a cooperative group of government representatives and non-governmental organisations lobbying for the promotion of sound environmental management of chemicals is calling for the ban of persistent organic pollutants. Efforts to control the use and trade of restricted or banned chemicals have led to the development of the Prior Informed Consent (PIC) Treaty, a proposed convention that would require exporting countries to provide information on whether the chemical they are exporting is restricted or banned nationally. ,p> However, the effectiveness of the PIC has been questioned by environmentalists who assert that the United Nations maintains a list of more than 700 products from 93 countries whose consumption or sale has been banned or severely restricted. Only 12 out of 25 000 pesticide products and five industrial chemicals out of thousands are on the proposed PIC list.

Source: SARDC, Southern African Features, 23 April 1997

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Copyright Chris Lungu, SACCAR, Private Bag 00108, Gaborone, Botswana email address: