Reply #22: It was essentially banned worldwide [View All]

Restrictions on usage

In the 1970s and 1980s, agricultural use of DDT was banned in most developed countries. DDT was first banned in Hungary in 1968<26> then in Norway and Sweden in 1970 and the US in 1972, but was not banned in the United Kingdom until 1984. The use of DDT in vector control has not been banned, but it has been largely replaced by less persistent alternative insecticides.

The Stockholm Convention, which entered into force in 2004, outlawed several persistent organic pollutants, and restricted the use of DDT to vector control. The Convention has been ratified by more than 160 countries and is endorsed by most environmental groups. Recognizing that a total elimination of DDT use in many malaria-prone countries is currently unfeasible because there are few affordable or effective alternatives, the public health use of DDT was exempted from the ban until alternatives are developed. The Malaria Foundation International states that "The outcome of the treaty is arguably better than the status quo going into the negotiations…For the first time, there is now an insecticide which is restricted to vector control only, meaning that the selection of resistant mosquitoes will be slower than before."<27>

Despite the worldwide ban on agricultural use of DDT, its use in this context continues in India<28> North Korea, and possibly elsewhere.<13>

Today, about 4-5,000 tonnes of DDT are used each year for vector control.<13> In this context, DDT is applied to the inside walls of homes to kill or repel mosquitos entering the home. This intervention, called indoor residual spraying (IRS), greatly reduces environmental damage compared to the earlier widespread use of DDT in agriculture. It also reduces the risk of resistance to DDT.<29> This use only requires a small fraction of that previously used in agriculture; for example, the amount of DDT that might have been used on 40 hectares (100 acres) of cotton during a typical growing season in the U.S. is estimated to be enough to treat roughly 1,700 homes.<30>

When a mosquito strain that had previously been eliminated returned to South Africa, it was resistant to the pyrethroid insecticides that had replaced DDT.

"The resulting increase in malaria cases and deaths was epidemic," Bouwman said. Cases soared from 4,117 in 1995 to 64,622 in 2000. "South Africa had to fall back on DDT, and still uses it in areas where other chemicals would have a risk of failure," he said.