Aldrin

Aldrin (SC POPs) is organochlorine pesticide manufactured commercially since 1950s and used throughout the world up to the early 1970s. Aldrin was used as insecticide in agriculture for the control of many soil pests and in the treatment of seed. Insects controlled by these compounds include termites, grasshoppers, wood borers, beetles, and textile pests. Aldrin (and also dieldrin) act as a contact and stomach poison for insects. Since the early 1970s, compound has been severely restricted or banned, in a number of countries, from use, especially in agriculture. Nevertheless, the use for termite control continues in other countries.

Aldrin is a pesticide used to control soil insects such as termites, corn rootworm, wireworms, rice water weevil, and grasshoppers. Aldrin is a highly effective broad-spectrum soil insecticide. It kills insects by contact and ingestion, and possesses slight fumigant action within the soil, which ensures distribution in the top soil where the pests are found. It is used to control soil insects, including termites, corn rootworms, seed corn beetle, seed corn maggot, wireworms, rice water weevil, grasshoppers, and Japanese beetles, etc. Crops protected by aldrin soil treatment include corn and potatoes; it is used as a seed dressing on rice.

Aldrin was used as insecticides in agriculture and also used for the protection of wooden structures against termite attack. It is supplied mainly as an emulsifiable concentrate or wettable powder.

A major use of aldrin is as a soil insecticide. Hence, aldrin-treated soil is an important source of aldrin and its reaction product dieldrin in the environment. Aldrin has a low propensity for movement away from treated areas, either through volatilization or by leaching. It is mainly and rapidly adsorbed on soils with a high organic matter content, but only moderately adsorbed by clay soils. Aldrin and dieldrin rarely penetrate more than 20 cm beneath the top treated layer of soil. Aldrin adheres to soil particles to such an extent that only traces can be removed by water. For this reason, contamination of ground water does not generally occur. The disappearance of aldrin from soil resembles a first-order reaction. Immediately after application, there is a short period of rapid loss due to volatilization and thereafter a second longer exponential period of decline, mainly due to conversion to dieldrin, which is slower to dissipate. However, there is the possibility of migration by way of soil erosion, as wind drift, sediment transport, and surface run-off. From data on residues of aldrin in the environment, it appears that it is mainly retained in the soil and that 97% of the primary residue is not the parent compound but its epoxide, dieldrin. Aldrin applied to soils is lost slowly in temperate areas, three-quarters of the applied aldrin being lost during the firstyear in a typical case. The rate of loss slows later as aldrin is converted to dieldrin. There is some evidence that the rate of lossis greater under the anaerobic conditions of rice paddies than underaerobic conditions. Dieldrin is lost from the soil very rapidly intropical areas, up to 90% disappearing within 1 month, whereas thehalf-life of dieldrin in temperate soils is approximately 5 years. Volatilization appears to be the principal route of loss from the soil, though atmospheric levels of dieldrin and aldrin are generally low. Some dieldrin is washed from the atmosphere by rain, but levels in ground water are very low because of strong adsorption to soil particles. Dieldrin has been detected, in small amounts, in surface water contaminated by run-off from agricultural land.

Experimental log K_oc values for aldrin range from 4.9 to 7.67. Based on a classification scheme, these log K_oc values indicate that aldrin is expected to be immobile in soil. The mobility of Aldrin and Dieldrin in the soil environment, however, can be enhanced at hazardous waste sites where organic solvents may be present. These organic solvents have the ability to increase the water solubility of nonpolar compounds which in turn increases their mobility in soil. Volatilization of Aldrin from soil is more rapid when it is applied to the soil surface rather than incorporated into the soil. A loss of 50% from a surface application was estimated to occur within 12 weeks after application compared to 1015 weeks for soil incorporated aldrin. The relatively rapid loss of both Aldrin and Dieldrin from soil during the first few months after application has been attributed to loss by volatilization. Based upon a Henry's law constant, volatilization of aldrin from water surfaces is expected, however, may be attenuated by adsorption to suspended solids and sediment in the water column. According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere, Aldrin will exist in both the vapour and particulate phases in the ambient atmosphere. Particulate phase Aldrin may be transported through the atmosphere by wind and later removed from air by wet and dry deposition. The preliminary indicator of potential bioaccumulation of a compound, log Kow, for Aldrin ranges from 5.68 to 7.40, indicating a high potential for bioaccumulation. Experimental evidence indicates that aldrin is rapidly metabolized to Dieldrin by some organisms, which then bioconcentrates and biomagnifies.

Aldrin and dieldrin are highly toxic for human beings. Severe cases of both accidental and occupational poisoning have occurred but only rarely have fatalities been reported. The lowest dose with a fatal outcome has been estimated to be 10 mg.kg^-1 body weight. Survivors of acute or subacute intoxications recovered completely. Irreversible effects or residual pathology have not been reported. Adverse effects from aldrin and dieldrin are related to the level of dieldrin in the blood. Determination of the level of dieldrin in the blood provides a specific diagnostic test of aldrin/dieldrin exposure. The level of dieldrin in the blood of male workers below which adverse effects do not occur, (the threshold no-observed-adverse-effect level) is 105 µg/litre blood. This corresponds to a daily intake of 0.02 mg dieldrin/kg body weight per day. Environmental exposure (mainly dietary though also, to a small extent, respiratory) leads to the presence of dieldrin at very low levels in organs, adipose tissue, blood, and mother's milk. As far as can be judged from the extensive clinical and epidemiological studies, there is no reason to believe that these prevailing body burdens constitute a health hazard for the general population. In a continuing study lasting more than 20 years, involving more than 1000 industrial workers in an aldrin/dieldrin insecticide-manufacturing plant, no increase in cancer incidence occurred among workers who had been exposed to high levels of aldrin and dieldrin. More significantly, there were no signs of any premonitory change in liver function in these workers. An epidemiological mortality study was carried out at a manufacturing plant in the USA on a cohort of 870 workers exposed to aldrin, dieldrin, and endrin. With almost 25 000 man-years of observation, no specific cancer risk associated with employment at this plant could be identified. Epidemiological studies examining cancer mortality in two series of workers exposed to aldrin provide no conclusive evidence of carcinogenicity in humans. Possible increases in liver, biliary, and rectal cancer were suggested in some of the later studies. Several studies in mice have shown that oral exposure to aldrin caused an increase in the incidence of malignant liver tumours. However, studies in rats have been either equivocal or flawed. Toxicokinetic data do not indicate that any different response would be expected following exposures by these routes. Accumulating evidence indicates that aldrin is nongenotoxic tumour promoter acting through species specific susceptibility of the mouse to induction of oxidative stress and inhibition of gap junctional communication. The Department of Health and Human Services (DHHS) has not listed aldrin in the U.S. National Toxicology Program Carcinogen List. The International Agency for Research on Cancer (IARC) determined that aldrin is unclassifiable because the carcinogenicity data are incomplete or ambiguous. According to the U.S. EPA Carcinogen List there is a sufficient evidence of aldrin carcinogenicity from animal studies with inadequate or no data from epidemiologic studies in humans, there for it is classified as a Category B2, Probable human carcinogen.

Since the introduction of the method of gas-liquid chromatography with electron capture detection (GLC/EC), old methods, based on, for instance, total organicchlorine or the colorimetric phenyl azide procedure, have been abandoned. The great majority of analytical data relating to the occurrence of residues of aldrin or dieldrin since that time have been based on GLC/EC procedures. There has been considerable evolution of various aspects (especially extraction and clean up procedures) of the methodology.

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[6] ATSDR: Agency for toxic substances and disease registery, http://www.atsdr.cdc.gov/

[7] TOXNET: TOXikology Data NETwork TOXNET - http://toxnet.nlm.nih.gov/

[8] IRZ: Integrovaný registr znečišťování životního prostředí (IRZ) : http://www.irz.cz/