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| Names | |
|---|---|
| Preferred IUPAC name (1R,4S,4aS,5S,8R,8aR)-1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5,8-dimethanonaphthalene | |
| Other names | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.005.652 |
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII | |
| UN number | 2762, 2761 |
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| Properties | |
| C12H8Cl6 | |
| Molar mass | 364.90 g·mol−1 |
| Appearance | Colorless solid |
| Density | 1.60 g/mL[1] |
| Melting point | 104 °C (219 °F; 377 K) |
| slightly soluble (0.003%)[1] | |
| Vapor pressure | 7.5 × 10−5 mmHg @ 20 °C |
| Pharmacology | |
| Legal status | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Toxic and is a suspected humancarcinogen[1] |
| GHS labelling: | |
   | |
| Danger | |
| H300,H301,H310,H311,H351,H372,H410 | |
| P201,P202,P260,P262,P264,P270,P273,P280,P281,P301+P310,P302+P350,P302+P352,P308+P313,P310,P312,P314,P321,P322,P330,P361,P363,P391,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 66 °C (151 °F; 339 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 50 mg/kg (rabbit, oral) 33 mg/kg (guinea pig, oral) 39 mg/kg (rat, oral) 44 mg/kg (mouse, oral)[2] |
LCLo (lowest published) | 5.8 mg/m3 (rat, 4 hr)[2] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 0.25 mg/m3 [skin][1] |
REL (Recommended) | Ca TWA 0.25 mg/m3 [skin][1] |
IDLH (Immediate danger) | 25 mg/m3[1] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Aldrin is anorganochlorine insecticide that was widely used until the 1990s, when it was banned in most countries. Aldrin is a member of the so-called "classic organochlorines" (COC) group of pesticides. COCs enjoyed a very sharp rise in popularity during and afterWorld War II. Other noteworthy examples of COCs includedieldrin andDDT.[3] After research showed that organochlorines can be highly toxic to the ecosystem throughbioaccumulation, most were banned from use. Before the ban, it was heavily used as a pesticide to treat seed and soil. Aldrin and related "cyclodiene" pesticides (a term for pesticides derived fromHexachlorocyclopentadiene) became notorious aspersistent organic pollutants.[4]
Pure aldrin takes form as a white crystalline powder. Though it is not soluble in water (0.003% solubility), aldrin dissolves very well in organic solvents, such asketones andparaffins.[5] Aldrin decays very slowly once released into the environment. Though it is rapidly converted todieldrin by plants and bacteria, dieldrin maintains the same toxic effects and slow decay of aldrin.[6] Aldrin is easily transported through the air by dust particles. Aldrin does not react with mild acids or bases and is stable in an environment with a pH between 4 and 8. It is highly flammable when exposed to temperatures above 200 °C[7] In the presence ofoxidizing agents aldrin reacts with concentrated acids and phenols.
Aldrin is not formed in nature. It is named after the German chemistKurt Alder, one of the coinventors of this kind of reaction. Aldrin is synthesized by combininghexachlorocyclopentadiene withnorbornadiene in aDiels-Alder reaction to give the adduct.[8] In 1967, the composition of technical-grade aldrin was reported to consist of 90.5% of hexachlorohexahydrodimethanonaphthalene (HHDN).[6]
Similarly, anisomer of aldrin, known asisodrin, is produced by reaction of hexachloronobornadiene withcyclopentadiene.[9] Isodrin is also produced as a byproduct of aldrin synthesis, with technical-grade aldrin containing about 3.5% isodrin.[6]
An estimated 270 million kilograms of aldrin and related cyclodiene pesticides were produced between 1946 and 1976.[10] The estimated production volume of aldrin in the US peaked in the mid-1960s at about 18 million pounds (8.2 kt) a year and then declined.[11]
There are multiple available forms of aldrin. One of these is the isomerisodrin, which cannot be found in nature, but needs to be synthesized like aldrin. When aldrin enters the human body or the environment it is rapidly converted todieldrin. Degradation by ultraviolet radiation or microbes can convert dieldrin tophotodieldrin and aldrin tophotoaldrin.[6]
Even though many toxic effects of aldrin have been discovered, the exact mechanisms underlying the toxicity are yet to be determined. The only toxic aldrin induced process that is largely understood is that of neurotoxicity.
One of the effects that intoxication with aldrin gives rise to isneurotoxicity. Studies have shown that aldrin stimulates thecentral nervous system (CNS), which may cause hyperexcitation andseizures.[12] This phenomenon exerts its effect through two different mechanisms.
One of the mechanisms uses the ability of aldrin to inhibit braincalcium ATPases.[13] These ion pumps relieve the nerve terminal from calcium by actively pumping it out. However, when aldrin inhibits these pumps, the intracellular calcium levels rise. This results in an enhancedneurotransmitter release.
The second mechanism makes use of aldrin's ability toblock gamma-aminobutyric acid (GABA) activity.[14] GABA is a major inhibitory neurotransmitter in the central nervous system. Aldrin induces neurotoxic effects by blocking theGABAA receptor-chloride channel complex. By blocking this receptor, chloride is unable to move into the synapse, which prevents hyperpolarization of neuronal synapses. Therefore, the synapses are more likely to generate action potentials.
The metabolism of oral aldrin exposure has not been studied in humans. However, animal studies are able to provide an extensive overview of the metabolism of aldrin. This data can be related to humans.
Biotransformation of aldrin starts withepoxidation of aldrin bymixed-function oxidases (CYP-450),[15] which forms dieldrin. This conversion happens mainly in the liver. Tissues with low CYP-450 expression use theprostaglandin endoperoxide synthase (PES) instead.[16] This oxidative pathway bisdioxygenises thearachidonic acid toprostaglandin G2 (PGG2). Subsequently, PGG2 is reduced toprostaglandin H2 (PGH2) by hydroperoxidase.
Dieldrin can then be directly oxidized by cytochrome oxidases, which forms 9-hydroxydieldrin. An alternative for oxidation involves the opening of the epoxide ring by epoxide hydrases, which forms the product 6,7-trans-dihydroxydihydroaldrin.[17] Both products can be conjugated to form 6,7-trans-dihydroxydihydroaldrin glucuronide and 9-hydroxydieldrin glucuronide, respectively. 6,7-trans-dihydroxydihydroaldrin can also be oxidized to form aldrin dicarboxylic acid.[18][19]
Considering thetoxicokinetics of aldrin in the environment, the efficacy of the compound has been determined. In addition, theadverse effects after exposure to aldrin are demonstrated, indicating the risk regarding the compound.
The ability of aldrin, in its use for the control of termites, is examined in order to determine the maximum response when applied. In 1953 US researchers tested aldrin and dieldrin on terrains with rats known to carrychiggers, at a rate of 2.25 pounds per acre (2.52 kg/ha). The aldrin and dieldrin treatment demonstrated a decrease of 75 times less chiggers on rats for dieldrin treated terrains and 25 times less chiggers on the rats when treated with aldrin. The aldrin treatment indicate a high productivity, especially in comparison to other insecticides that were used at the time, such asDDT,sulfur orlindane.[20]
Exposure of aldrin to the environment leads to the localization of the chemical compound in the air, soil, and water.[6] Aldrin gets changed quickly to dieldrin and that compound degrades slowly, which accounts for aldrin concentrations in the environment around the primary exposure and in the plants.[21] These concentrations can also be found in animals, which eat contaminated plants or animals that reside in the contaminated water. Thisbiomagnification can lead to a high concentrations in their fat.
There are some reported cases of workers who developedanemia after multiple dieldrin exposures. However the main adverse effect of aldrin and dieldrin is in relationship to the central nervous system.[6] The accumulated levels of dieldrin in the body were believed to lead toconvulsions.[22] Besides that other symptoms were also reported like headaches, nausea and vomiting, anorexia, muscle twitching and myoclonic jerking andEEG distortions. In all these cases removal of the source of exposure to aldrin/dieldrin led to a rapid recovery.[23]
The toxicity of aldrin and dieldrin is determined by the results of several animal studies. Reports of a significant increase in workers death in relation to aldrin has not been found, although death by anemia is reported in some cases after multiple exposure to aldrin. Immunological tests linked an antigenic response toerythrocytes coated with dieldrin in those cases.[24] Direct dose-response relations being a cause for death are yet to be examined.
TheNOAEL that was derived from rat studies:[6]
In addition to these studies, breast cancer risk studies were performed demonstrating a significant increased breast cancer risk. After comparing blood concentrations to number of lymph nodes and tumor size a 5-fold higher risk of death was determined, comparing the highest quartile range in the research to the lower quartile range.[25]
Most of the animal studies done with aldrin and dieldrin used rats. High doses of aldrin and dieldrin demonstratedneurotoxicity, but in multiple rat studies also showed a unique sensitivity of the mouse liver to dieldrin inducedhepatocarcinogenicity.[26] Furthermore, aldrin treated rats demonstrated an increasedpost-natal mortality, in which adults showed an increased susceptibility to the compounds compared to children in rats.[27]
Like related polychlorinated pesticides, aldrin is highly lipophilic. Its solubility in water is only 0.027 mg/L, which exacerbates its persistence in the environment. It was banned by theStockholm Convention on Persistent Organic Pollutants. In the U.S., aldrin was cancelled in 1974. The substance is banned from use for plant protection by theEU.[28]
Aldrin has ratLD50 of 39 to 60 mg/kg (oral in rats). For fish however, it is extremely toxic, with anLC50 of 0.006–0.01 fortrout andbluegill.[4]
In the US, aldrin is considered a potential occupational carcinogen by theOccupational Safety and Health Administration and theNational Institute for Occupational Safety and Health; these agencies have set an occupational exposure limit for dermal exposures at 0.25 mg/m3 over an eight-hour time-weighted average.[29]Further, anIDLH limit has been set at 25 mg/m3, based on acute toxicity data in humans to which subjects reacted with convulsions within 20 minutes of exposure.[30]
It is classified as anextremely hazardous substance in the United States as defined in Section 302 of the U.S.Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[31]
