DDT

Dichlorodiphenyltrichloroethane (DDT) is a synthetic organochlorine insecticide that became one of the most widely used pesticides of the 20th century. It is a colorless, odorless solid at room temperature and is highly persistent in the environment due to its chemical stability and lipophilicity. DDT is composed of two phenyl rings substituted with chlorine and a central ethane moiety; it exists in two main isomeric forms, o,p′-DDT and p,p′-DDT, with the latter being more biologically active.

History and discovery: DDT was first synthesized in 1874, but its insecticidal properties were discovered in 1939 by Paul Hermann Müller, who received the 1948 Nobel Prize in Physiology or Medicine for this work. Its use expanded rapidly in agriculture and malaria control after World War II.

Usage and mechanism: DDT acts as a broad-spectrum insect neurotoxin, affecting sodium channel function in nerve cells. It has long residual activity, remaining in soil and sediments for years, contributing to persistent exposure in ecosystems.

Environmental impact and regulation: DDT is extremely persistent and bioaccumulative, leading to biomagnification in food chains. It has been linked to adverse effects on wildlife, notably eggshell thinning in birds of prey. These environmental concerns led to major restrictions in many countries in the 1960s and 1970s, with the United States banning production and most uses in 1972, and global restrictions under the Stockholm Convention on Persistent Organic Pollutants in 2001. Nevertheless, DDT remains permitted in some malaria-control programs when safer alternatives are not available, under strict conditions.

Health effects and current status: human health effects are the subject of ongoing research; some studies suggest associations with cancer and reproductive effects, but evidence is not conclusive. Today, DDT is largely restricted to vector-control applications in limited contexts, while alternatives and integrated vector management are emphasized.