Why was the use of DDT banned in the US? The 1972 EPA order
EPA banned nearly all US uses of DDT in 1972 over wildlife damage and potential human health risks. Public health, quarantine and minor crop uses stayed.
Why was the use of DDT banned in the US?
EPA banned nearly all uses of DDT in the US in 1972 because it persists in the environment, builds up in fatty tissue and food chains, harmed wildlife and posed potential human health risks (EPA history, EPA review).
EPA Administrator William D. Ruckelshaus issued the cancellation order on June 14, 1972. It took effect on December 31, 1972 (EPA, order text).
What is DDT?
DDT stands for dichlorodiphenyltrichloroethane. Its chemical name in the EU POPs Regulation is 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, CAS 50-29-3 (legislation.gov.uk). Developed in the 1940s, it was the first modern synthetic insecticide. Military and civilian programs used it against malaria, typhus and other insect-borne diseases. Insects later developed resistance (EPA).
How the 1972 ban came about
Rachel Carson's Silent Spring (1962) raised public concern about pesticide use and the need for better controls (EPA). From 1967 the Environmental Defense Fund became increasingly active in court cases against DDT (EPA 1975 survey).
EPA issued cancellation notices in January 1971 under a court order that followed an EDF suit. A hearing on all remaining uses opened in August 1971 and heard 125 expert witnesses before the 1972 order (EPA 1975 survey).
The reasons EPA gave
Ruckelshaus said he was "convinced that the continued massive use of DDT posed unacceptable risks to the environment and potential harm to human health" (EPA). EPA's 1975 review sums up the case as "findings of persistence, transport, biomagnification, toxicological effects", plus the fact that effective, less harmful substitutes existed (EPA 1975 survey).
The 1972 order wasn't a total ban. It excepted public health and quarantine uses, exports and three minor crop uses: green peppers, onions and sweet potatoes in storage (EPA, order text). Manufacturers sued. On December 13, 1973 the US Court of Appeals for the D.C. Circuit found "substantial evidence" for the order (EPA 1975 survey).
DDT's effects on wildlife
Eggshell thinning in birds of prey is "perhaps the best known toxic effect of DDT", according to the Stockholm Convention Secretariat (pops.int). The main culprit was DDE, DDT's breakdown product (EPA 1983).
Bald eagles took it in through contaminated fish, and their eggs had shells so thin they often broke during incubation. By 1963 the lower 48 states had only 417 nesting pairs (FWS). When the brown pelican was delisted in 2009, FWS said its recovery was "largely due to the federal ban on the general use of the pesticide DDT in 1972" (FWS).
DDT can travel long distances in the upper atmosphere (EPA). It also lingers. Up to 50% can remain in soil 10 to 15 years after application, and residues turn up in the Arctic, in food worldwide and in breast milk (pops.int).
DDT's effects on humans
People who swallowed large amounts of DDT by accident had tremors, headaches, nausea and seizures. Animal studies show effects on the nervous system, liver and reproductive system, generally at doses above likely US exposures (ATSDR). For the general population, food is the main exposure route (pops.int). ATSDR notes that people with higher blood levels of DDT have a higher risk of liver cancer (ATSDR).
IARC classified DDT as "probably carcinogenic to humans (Group 2A)" on 23 June 2015, based on sufficient evidence in animals and limited evidence in humans (IARC). EPA's IRIS rating is B2, probable human carcinogen, last updated in 1988 (EPA IRIS). Neither rating proves DDT causes cancer in people.
Is DDT still allowed anywhere?
Yes, for malaria and other disease vector control. The Stockholm Convention lists DDT in Annex B. Its only acceptable purpose is disease vector control. Use must follow WHO guidance and is allowed only "when locally safe, effective and affordable alternatives are not available". Parties using DDT report every three years. The Conference of the Parties reviews the need for it at least every three years (Convention text).
India, Ethiopia and Namibia are listed for production and use in the DDT Register. Other Parties are listed for use only. Registration does not prove current use or replace the treaty's conditions (pops.int register). The old specific exemption, DDT as an intermediate for dicofol, is no longer available (specific exemptions). In the EU, DDT sits in Annex I Part A of the POPs Regulation (EU) 2019/1021 with no exemption, so its production, placing on the market and use are prohibited (legislation.gov.uk). The US signed the Convention on May 23, 2001 but has not ratified it (UN Treaty Collection).
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