DDT for Malaria Control DDT is among several tools used today to fight malaria in developing nations. Other tools include bednets, medical treatments, and other pesticides. However, DDT has proven to be most affordable and effective tool and for this reason should remain part of malaria control programs. In 1990, DDT was determined to cost two to 23 times less than other alternatives, and recent assessments find that it remains the most affordable insecticide (see: K. Walker, Cost Comparison of DDT and Alternative Insecticides for Malaria Control,” Medical and Veterinary Entomology 14, 2000: 345-354). Sadly, DDT prices have increased because of declining production, which is related to political campaigns to regulate and ban the substance. As far as we know, the type of malaria that infects humans does not infect wildlife, which means the malaria parasite needs human hosts to survive. Accordingly, if human transmission could be prevented the malaria parasite would die off because of the lack of access to hosts. In most of developed world, public health officials eradicated malaria by preventing human exposure in large part through DDT programs. In addition, development also greatly reduced transmission of all types of mosquito-borne diseases because most people in developed countries now live in sealed homes—homes with screens and sealed windows that keep mosquitoes out. Air conditioning also plays a role because it enables people to keep windows closed. In developing nations, controlling malaria is much more difficult because mosquitoes have greater access to the insides of homes. Mosquitoes enter homes—huts and other unsealed structures—freely and feed on people at night while they sleep. The use of insecticide-treated bednets can be helpful, but the benefits have been limited for a number of reasons: the nets are expensive, are often not used properly, can become damaged, and must be retreated or replaced relatively frequently. In addition, people often choose not to use them in hot climates because they reduce ventilation. DDT is particularly helpful in these conditions, requiring limited applications where people live, rather than widespread application in the environment as was common in the 1950s and 1960s. Today, public health officials can spray DDT in and around huts and other residential structures to prevent human exposure in large part by repelling mosquitoes. In essence, DDT acts as a chemical “screen,” keeping mosquitoes away and killing the few that might enter homes. It also does not require that people do anything to make it work each night, and it’s relatively inexpensive. Because DDT is persistent (i.e., it does not break down quickly), it works a long time without the need of constant reapplication. Ironically, DDT is subject to regulations and bans around the world because of its persistence in the environment; yet this persistence is one of DDT’s key public health benefits. Next