Dieldrin

Dieldrin is an organochlorine compound that was originally produced in 1948 as an insecticide[1]. It is closely related to aldrin, which reacts to form dieldrin. Aldrin is not toxic to insects, but it is oxidized in the insect to form dieldrin, which is the active compound[1]. Both dieldrin and aldrin are named after the Diels-Alder reaction used to form aldrin from a mixture of norbornadiene and hexachlorocyclopentadiene[1].

Dieldrin was developed in the 1940s as an alternative to DDT and proved to be a highly effective insecticide, widely used during the 1950s to early 1970s[1]. However, it is an extremely persistent organic pollutant that does not easily break down and tends to biomagnify as it is passed along the food chain[1]. Long-term exposure has been proven toxic to a wide range of animals, including humans, and has been linked to health problems such as Parkinson's, breast cancer, and immune, reproductive, and nervous system damage[1][5]. It is also an endocrine disruptor, acting as an estrogen and antiandrogen, and can adversely affect testicular descent in the fetus if a pregnant woman is exposed to it[1].

The production of dieldrin involves the Diels-Alder reaction of hexachloro-1,3-cyclopentadiene with norbornadiene, followed by epoxidation of the addition product with a peroxy acid such as peracetic acid[1]. Technical dieldrin contains 5-15% related polychloroepoxyoctahydro-dimethanonaphthalenes[1]. The estimated combined production volume of aldrin and dieldrin in the US peaked in the mid-1960s at about 20 million pounds a year (2 million pounds of dieldrin) and then declined[1].

Dieldrin and aldrin were widely applied in agricultural areas throughout the world to control subterranean insect pests such as nargles root maggots, mole cricket grubs, and weevils[1]. Both are toxic and bioaccumulative, with aldrin breaking down to dieldrin in living systems, but dieldrin resisting bacterial and chemical breakdown processes in the environment[1]. Both dieldrin and aldrin have been banned in most developed countries, but aldrin is still used as a termiticide in some countries[1].

Aldrin and dieldrin are acutely toxic to laboratory animals by the oral, dermal, and inhalation routes, and are mildly irritating to the eye and skin[2]. They affect the central nervous system, producing irritability, tremors, and convulsions[2]. The EPA issued suspension notices for aldrin and dieldrin in 1974 due to carcinogenicity data and other information, including laboratory data indicating a significant increase in liver tumors in mice fed a diet containing dieldrin, and detectable residues of dieldrin in human fat tissues[2].

The current permissible workplace exposure limit for aldrin and dieldrin enforced by the Occupational Safety and Health Administration is 0.25 mg/m³, and the ACGIH has recommended a TLV-TWA of 0.25 mg/m³ and a TLV-STEL of 0.75 mg/m³[2][4]. Despite being banned in most of the world, dieldrin may still have uses, such as controlling plague by killing the Oriental rat flea that transmits the bacterium Yersinia pestis from rats to humans[3]. However, due to its persistence and toxicity, exploring other ways to eradicate plague is recommended[3].

In summary, dieldrin is a highly effective but extremely persistent and toxic insecticide that has been banned in most developed countries due to its impact on human health and the environment.

Citations:

[1] https://en.wikipedia.org/wiki/Dieldrin

[2] https://www.ncbi.nlm.nih.gov/books/NBK217623/

[3] https://www.acs.org/molecule-of-the-week/archive/d/dieldrin.html

[4] https://www.cdc.gov/niosh/idlh/60571.html

[5] https://www.bcpp.org/resource/dieldrin-and-aldrin/