See also:
Dieldrin summary in Assessment report on POPs, Français, Español
Rotterdam Convention Decision Guidance Documents on Dieldrin: English, Français, Español

Chemical properties

CAS chemical name: 3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-dimetanonapth[2,3-b]oxirene.
Synonyms and Trade Names (partial list):Alvit, Dieldrite, Dieldrix, Illoxol, Panoram D-31, Quintox.
CAS No.:60-57-1;
Molecular formula: C12H8Cl6O;
Formula weight: 380.91.
Appearance: A stereo-isomer of endrin, dieldrin may be present as white crystals or pale tan flakes, odourless to mild chemical odour.
Properties: Melting point: 175-176 C; boiling point: decomposes; KH: 5.8 x 10-5 atm.m3/mol at 25 C; log KOC: 4.08-4.55; log KOW: 3.692-6.2; solubility in water: 140 µg/L at 20 C; vapour pressure: 1.78 x 10-7 mm Hg at 20 C.

Historical Uses

Dieldrin has been used in agriculture for the control of soil insects and several insect vectors of disease but this latter use has been banned in a number of countries due to environmental and human health concerns. Principle contemporary uses are restricted to control termites and wood borers and against textile pests (WHO, 1989).

Action to ban dieldrin has been taken in many countries, including Bulgaria, Ecuador, the EU, Hungary, Israel, Portugal, Singapore, Sweden, and Turkey. Its use is severely restricted in numerous countries, including Argentina, Austria, Canada, Colombia, Cyprus, India, Japan, New Zealand, Pakistan, USA and Venezuela.

Human Health and Environmental Issues

Dieldrin binds strongly to soil particles and hence is very resistant to leaching into groundwater. Volatilization is an important mechanism of loss from the soil and, because of its persistent nature and hydrophobicity, dieldrin is known to bioconcentrate.

In a study using human volunteers, the subjects received dieldrin daily for 2 years. All the volunteers continued in excellent health, and clinical, physiological and laboratory findings remained essentially unchanged through the exposure period and an 8 month follow up. In a study of workers from a plant involved in the manufacture of aldrin, dieldrin and endrin, a statistically significant increase in liver and biliary tract cancers was observed, although the study did have some limitations, including lack of quantitative exposure information.

In laboratory studies, acute oral LD50 values in the range of 37 mg/kg body weight in rats to 330 mg/kg in hamsters have been found for dieldrin. As with other organochlorine compounds, the liver is the major target organ in rats, with effects that included increased liver/body weight ratio, hypertrophy and histopathological changes. The no observed adverse effect level (NOAEL) in rats is 0.5 mg/kg diet, equal to 0.025 mg/kg body weight/day. When rats were fed dieldrin in their diet over three generations, no changes in reproductive capacity were observed at any dose level tested. A NOAEL of 2 mg dieldrin /kg diet has been set for reproduction in rats. There was no evidence for teratogenic potential in studies in rats, mice or rabbits using oral doses of up to 6 mg/kg body weight. Abnormal development and fetotoxicity were observed in hamsters and mice, however, these results are unlikely to be of significance in view of the maternal toxicity noted at the high dose levels.

There is limited evidence that cyclodienes such as dieldrin may affect immune responses. IARC has concluded that there is inadequate evidence for the carcinogenicity of dieldrin in humans, and limited evidence in experimental animals and has been classified by IARC in Group 3.

Dieldrin has low phytotoxicity. Plants are affected only by application rates much higher than suggested use rates.

The acute toxicity of dieldrin is quite variable for aquatic invertebrates, with insects being the most sensitive group (values range from 0.2-40 µg/L). It is highly toxic to most species of fish tested in the laboratory (values range from 1.1-41 µg/L). Acute toxicity of dieldrin in frogs (96-h LC50) ranged from 8.7 µg/L for Rana catesbeiana tadpoles to 71.3µg/L for the tadpoles of Rana pipiens. Spinal deformities in embryo-larval tests were observed at concentrations as low as 1.3 µg/L for Xenopus laevis after a 10 day exposure.

The acute toxicity of dieldrin to avian species varies widely, with acute oral LD50 values in the range of 26.6 in pigeons to 381 mg/kg in mallard ducks. Mallard ducklings were exposed to dieldrin in the diet for 24 days. A 24 d NOAEL of 0.3µg dieldrin/g diet, based on growth impairment, was determined. Reproduction success in birds has not been consistently affected in the absence of maternal toxicity.

The acute LD50 of dieldrin to four species of voles range from 100 to 210 mg/kg body weight, suggesting that these microtine rodents are less susceptible than laboratory rodents to dieldrin. In another study, white tailed deer (Odocoileus virginianus) were fed diet containing dieldrin for up to 3 years. Adult survival was not affected, and fertility and in utero mortality was comparable for all groups. Fawns from treated does were smaller at birth, experienced greater postpartum mortality and weight gain was reduced. Blesbuck (Damaliscuc dorcas phillipsi) were fed diets containing dieldrin for 90 days. None of the animals fed 5 or 15 mg/kg diet died during the study period, but all animals at the higher dose levels died within 24 days.

The half life of dieldrin in temperate soils is approximately 5 years. This persistence, combined with high lipid solubility, provides the necessary conditions for dieldrin to bioconcentrate and biomagnify in organisms.

Bioconcentration factors of 12,500 and 13,330-May-2007!-- #EndDate --> that dieldrin is bioconcentrated by aquatic organisms rather than bioaccumulated.

Dieldrin's chemical properties (low water solubility, high stability, and semi-volatility) favour its long range transport, and dieldrin has been detected in arctic air, water and organisms. Dieldrin residues have been detected in air, water, soil, fish, birds and mammals, including humans and human breast milk.

As aldrin is readily and rapidly converted to dieldrin in the environment and in organisms, the levels of dieldrin detected likely reflect the total concentrations of both compounds.

In Egypt, the estimated dietary intake of dieldrin by breast fed infants of 1.22 µg/kg body weight/ day. Diet is the main30-May-2007eldrin was the second most common pesticide detected in a survey of US pasteurized milk, detected in 172 of the 806 composite samples tested, with a maximum level of 0.003 ppm. Dieldrin residues were detected in 9 of 602 (1.5%) samples of domestic animal fats and eggs in Canada, with a maximum of 0.050 mg/kg. Dieldrin was also detected in Spanish meat, residues of 20 to 40 ppb were detected in the fat of 8 to 15% of pork products (meat, cured sausage, pork bologna) and in 28% fresh poultry sausage. Dieldrin residues were detected in Oriental party beans at 3.45 ppb.

The average daily intake of aldrin and dieldrin in India was calculated to be 19 µg/person, exceeding the acceptable daily intake of 6.0 µg/60 kg of body weight recommended by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR). Dairy products, such as milk and butter, and animal meats were the primary sources of exposure. Exposure through food intake has been estimated at 0.55 µg/person in Vietnam.