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Environmental Engineering Chemistry II: Environmental Organic Chemistry Return to List of Fact SheetsIntroductionOrganochlorine insecticides are hydrocarbon compounds in which various numbers of hydrogen atoms have been replaced by Cl atoms. Commonly used in the 1960’s, application of organochlorine insecticides has been largely phased out because of their toxicities, environmental persistence, and accumulation in food chains. From a production perspective, most organochlorine insecticides have been replaced by less persistent chemicals, however their residues in solids and sediments still contribute to water pollution. These compounds are persistent because of their resistance to biological degradation and propensity to bioaccumulate in fatty tissues of biota (Royal Society of Chemistry, 1991; Smith, 1991; Mannahan, 1994).The following investigation of the environmental fate of three organochlorine insecticides (DDT, chlordane, and lindane) in a pond ecosystem was conducted with the Exposure Analysis Modeling System (EXAMS), Version 2.94, computer simulation model. EXAMS models chemical fate processes in natural environments, based upon physical and chemical properties of selected compounds and other assumed environmental conditions. These physical/chemical properties were obtained from the Illustrated Handbook of Physical/Chemical Properties and Environmental Fate for Organic Chemicals, Volume V, Pesticide Chemicals (MacKay, 1997), and were selected based upon the number of references for a given value and the methods of derivation (i.e., experimental vs. estimated data). Table 1 includes selected values, as well as chemical structures, of DDT, chlordane, and lindane. DDTProduction and UseOf the more notable organochlorine insecticides has been DDT (dichlorodiphenyltrichloroethane), which was used extensively following World War II for controlling mosquito-borne malaria and as an agricultural insecticide. Peak usage in the United States occurred in 1962, when 80 million kg of DDT were used and 82 million kg produced. Because of increasing environmental concern, production had declined to 2 million kg by 1971. The U.S. Environmental Protection Agency (EPA) announced in 1972 that DDT could no longer be used except in cases of public health emergency. In 1985, there were two DDT producers who exported approximately 303,000 kg. Current data on DDT production in the United States could not be obtained (Agency for Toxic Substances and Disease Registry [ATSDR], 1994a). DDT is available in various forms: aerosols, dustable powders, emulsifiable concentrates, granules, and wettable powders (Royal Society of Chemistry, 1991; Meister, 1992). Breakdown products of DDT include DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane), which are also highly persistent and have similar chemical and physical properties (World Health Organization [WHO], 1989; Augustijn-Beckers, et al., 1994).Physical/Chemical PropertiesMolecular weight: 354.5Vapor Pressure: 1.5 x 10-7 torr Henry’s law Constant: 1.3 x 10-5 atm-m3/mol Water Solubility: 0.003 mg/L Octanol/Water Partition Coefficient, Kow: 1.6 x 106 Sorption Partition Coefficient, Koc: 2.5 x 105 Melting Point (oC): 108.5 Boiling Point (oC): 185 Density (g/cm3 at 20oC): 1.55 Entry and Fate in the EnvironmentDDT is very persistent in the environment, with a reported half-life between 2-25 years (U.S. EPA, 1989; Augustijn-Beckers, et al., 1994) and is immobile in most soils. Routine loss and degradation include runoff, volatilization, photolysis, and biodegradation (both aerobic and anaerobic) (ATSDR, 1994a). Degradation processes are generally very slow (WHO, 1989; Augustijn-Beckers, et al., 1994).Due to its extremely low solubility in water, DDT is retained to a greater degree by soils and soil fractions with higher proportions of soil organic matter (WHO, 1989). Generally, DDT is tightly sorbed by soil organic matter, but it (along with its metabolites) has been detected in many locations in soil and groundwater where it may be available to organisms (U.S. EPA, 1989; WHO, 1989). This is probably due to its high persistence; although it is immobile or only very slightly mobile. Over very long periods of time DDT may be able to eventually leach into groundwater, especially through soils with little soil organic matter. Residues at the surface of the soil are much more likely to be broken down or otherwise dissipated than those below several inches (Matsumura, 1985). Studies in Arizona have shown that volatilization losses may be significant and rapid in soils with very low organic matter content (desert soils) and high irradiance of sunlight, with volatilization losses reported as high as 50% in 5 months (Jorgensen, et al., 1991). In other soils, this rate may be very low (<20% over 5 years) (Jorgensen, et al., 1991). Volatilization loss will vary with the amount of DDT applied, proportion of soil organic matter, proximity to soil-air interface and the amount of sunlight (WHO, 1989). DDT may reach surface waters primarily by runoff, atmospheric transport, drift, or by direct application (e.g. to control mosquito-borne malaria) (ATSDR, 1994a). The reported half-life for DDT in the water environment is 56 days in lake water and approximately 28 days in river water (U.S. EPA, 1989). The main pathways for loss is volatilization, photodegradation, adsorption to water-borne particulates and sedimentation (ATSDR, 1994a). Aquatic organisms, as noted above, also readily take up and store DDT and its metabolites. Field and laboratory studies in the United Kingdom demonstrated that very little breakdown of DDT occurred in estuary sediments over the course of 46 days (WHO, 1989). DDT has been widely detected in ambient surface water sampling in the United States at a median level of 1 ng/L (Van Ert and Sullivan, 1992, ATSDR, 1994a). Environmental Risk and ToxicityThe U.S. EPA has classified DDT as a Class II, moderately toxic chemical. Humans can be exposed to DDT primarily by eating food that contains small amounts of the compound. Even though DDT has not been used in the United States since 1972, small amounts of DDT are found in soils and can potentially be transferred to crops. Imported foods may have been directly exposed to DDT. In addition to soil residues, DDT and its breakdown products may still be found in water and air (ATSDR, 1994a).Short-term exposure to high doses of DDT affects primarily the central nervous system. Accidental ingestion by humans has caused excitability, tremors, and seizures. Exposure has also caused rashes or irritation to the eyes, nose, and throat. Long-term exposure of humans to low doses of DDT has produced changes in liver enzyme activity. Studies in laboratory animals have confirmed effects on the nervous system, and have also resulted in increased occurrence of liver tumors and reproductive impairment (ATSDR, 1994a). DDT is highly toxic to many aquatic invertebrate species. Reported 96-hour LC50s (concentration which causes mortality in 50% of test animals) in various aquatic invertebrates (e.g., stoneflies, midges, crayfish, sow bugs) range from 0.18 ug/L to 7.0 ug/L. Forty-eight-hour LC50s are 4.7 ug/L for daphnids and 15 ug/L for sea shrimp (Johnson and Finley, 1980). DDT is also highly toxic to fish species. Reported 96-hour LC50s are less than 10 ug/L in coho salmon (4.0 ug/L), rainbow trout (8.7 ug/L), bluegill sunfish (8.6 ug/L), largemouth bass (1.5 ug/L), and fathead minnow and channel catfish are 21.5 ug/L and 12.2 ug/L respectively (Johnson and Finley, 1980). DDT is also moderately toxic to some amphibian species and larval stages appear to be more susceptible than adults (Hudson et al. 1984; WHO, 1989). In addition to acute toxic effects, DDT may bioaccumulate significantly in fish and other aquatic species, leading to long-term exposure. This occurs mainly through uptake from sediment and water into aquatic flora and fauna. A half-time for elimination of DDT from rainbow trout was estimated to be 160 days (WHO, 1989). ChlordaneProduction and UseChlordane (1,2,4,5,6,7,8,8a-octachlor-2,3,3a,4,7,7a-hexahydro-4,7-methanoindane) was discovered in 1945 as a mixture of over 140 different compounds (Kirk-Othmer, 1995). It is synthesized first by Diel-Alder fusion between cyclopentadiene and hexachlorocyclopentadiene, forming chlordene. Chlordane is then produced by addition of two Cl-atoms across the double bond of chlordene at high temperature and pressure (Kirk-Othmer, 1995). This results in formation of two isomers of chlordane-a-trans and b-cis. The b-isomer has significantly greater insecticidal activity.At the height of production, chlordane was the second-most widely used organochlorine insecticide in the United States, with the annual production about 11 million kg per year. Its primary uses included soil and household insecticide (ATSDR, 1994b), preservative for wood and underground cables, and fire ant control in power transformers (ASTDR, 1989). Formulations previously available or available outside of the United States include dusts, emulsifiable concentrates, granules, oil solutions, and wettable powders (Meister, 1992). Over 70,000 tons of chlordane have been manufactured since 1946 (Dearth, 1990). Because of concern about the risk of cancer, all use of chlordane was cancelled in April 1988 (ATSDR, 1989). Physical/Chemical PropertiesMolecular weight: 409.8Physical Description: Viscous amber liquid with a chlorine like odor Vapor Pressure: 0.0000098 torr Henry’s law Constant: 0.000083 atm-m3/mol Water Solubility: 0.1 mg/L Octanol/Water Partition Coefficient: 1x106 Sorption Partition Coefficient: 2x104 Melting Point (oC): 103-105 (trans-isomer), 106-108 (cis-isomer) Boiling Point (oC): 175 Density (g/cm3 at 20oC): 1.59-1.63 Entry and Fate in the EnvironmentEnvironmental fate of chlordane is summarized below:
Chlordane enters the environment through the direct application to crops, lawns, and to control termites. It is very persistent in soil, sorbing strongly to organic particles. The half-life in soil is 4-20 years (ATSDR, 1994). Volatilization soil may be the only major route of chlordane entering air. Because it is insoluble in water and very rapid bind to soil, potential for surface and groundwater contamination is very low. However, in areas where chlordane was heavily used, low levels (0.01 to 0.001 ug/L) have been observed (U.S. EPA, 1990). Environmental Risk and ToxicityChlordane can enter the body via the gastrointestinal tract, skin, and respiratory system. Acute exposure to chlordane can result in headaches, confusion, vision problems, hypertension, ataxia, hyperactive, vomiting, diarrhea, convulsions and death (ASTDR, 1994a). Chronic exposure in mice caused a 50% decline in fertility and caused the development of liver cancer in rats. At cellular level, chlordane acts as an energy transfer inhibitor and an electron transport inhibitor (Review of Chlordane, 1988). Chlordane is also toxic to aquatic organisms. A 96-hour LC50 for mayflies is 4.3 ug/L, and for trout is 42-90 ug/L (Johnson and Finley, 1980).LindaneProduction and UseLindane, the gamma-isomer of hexachlorocyclohexane (HCH), is a colorless, crystalline solid, which is soluble in water. Commercial lindane is 99% gamma HCH. Technical- grade HCH is a mixture of isomers containing 64% alpha-, 10% beta-, 13% gamma-, 9% delta-, and 1% epsilon-HCH. It is produced by the chlorination of benzene under ultraviolet light. Commercial production of lindane began in the United States in 1945 and peaked in the 1950s, when 8 million kg of the compound were manufactured. Lindane has not been produced in the United States since 1977. However, it is still imported to and formulated in the United States. Its use is restricted by the U.S. EPA and can be applied only by certified applicator (Smith, 1991).Lindane is used primarily as an insecticidal treatment for hardwood logs and lumber, seed grains, and livestock. Other major uses are as an insecticide for several dozen fruit and vegetable crops, and for personal hygiene as a scabicide and pediculicide in the form of a lotion, cream, or shampoo. Agricultural uses accounted for about 95% of the lindane and other HCH isomers used in 1974; the remaining uses were industrial. Physical/Chemical PropertiesMolecular weight: 290.85Vapor Pressure: 3x10-5 torr @ 25 C Henry's Law Coefficient: 3x10-6 atm-m3/mol Water Solubility: 7.3 mg/L of water at 25 C; Slightly soluble in water Octanol/Water Partition (Kow): 5012 Soil sorption coefficient: average Koc = 1081; low soil mobility Melting Point (oC): 112.5 Boiling Point (oC): 323.4 Density/Spec. Grav.: 1.85 gr/cm3 @20 oC Entry and Fate in the EnvironmentLike other organochlorine insecticides, lindane can enter the environment through numerous pathways. Its half-life is 1.2 years in soil and can last up to 6.5 years, depending on soil type. Roughly 20% of the amount of lindane applied to soil is volatilized within 40 days (Brown, 1978; International Organization of Consumers Unions, 1986).In air, Lindane is thought to travel as small crystals in the atmosphere adhered to dust particles or water droplets. These crystals spend about 30 days in the atmosphere before they are washed out by rainfall. Lindane vapors on the other hand stay in the atmosphere for 2 to 4 months (Brown, 1978). When an air mass containing lindane comes in contact with a water body, air-water surface interactions occur. Once lindane enters the thin water surface layer it can either be evaporated or volatilized back out into the atmosphere or it can go into bulk concentration with the water. Once in the water, lindane can be taken up by aquatic life or be deposited into the sediment layer. In the sediment layer microorganisms can degrade lindane both aerobically and anaerobically. Microorganisms within the lake sediments convert lindane (Y-HCH) to mostly a-HCH and some d-HCH. The alpha isomer is about one quarter less toxic than lindane (Brown, 1978). Environmental Risk and ToxicityBecause lindane is internationally used, concentrations have been measured in the air and water around the world. Therefore, exposure occurs on a daily basis to humans and organisms on land or in aquatic environments. Since lindane is used extensively for agricultural purposes, residues are often found in fruits, vegetables, milk, and meat. It has been reported that the average daily lindane intake an adult receives from food is 0.14 µg. Drinking water contaminated with lindane is another common exposure pathway (U.S. Army, 1997). Although lindane concentrations in drinking water are generally low (0.05-0.1 ug/L), high concentrations may be a problem in localized areas. Breathing contaminated air near treated agricultural lands, industrial plants that manufacture lindane, and workplace air are other common ways humans are exposed to lindane. Because humans and animals can be exposed to lindane through various pathways, studies have been conducted to determine its toxicity (Smith, 1991).Short-term exposure of humans to lindane may interfere with transmission of nerve impulses, disrupting the function of the central nervous system. Acute effects of lindane exposure include nausea, vomiting, gastroenteritis, weakness, numbness, respiratory problems, behavioral disturbances, chloracne, hepatic damage, and renal injury. Excessive dermal or oral intake causes functional alterations in the nervous system in the form of seizures and uncontrollable eye movements. Lindane also appears to have a definite inhibitory effect on white blood cells in vitro. Chronic exposure may result in liver and kidney damage, hormonal disturbances, mental changes, weight loss joint pain, visual disturbances (Smith, 1991). Lindane is very toxic to fish, aquatic invertebrates, and amphibians. The 96-hour LC50 ranges from 1.7 to 32 ug/L for trout and salmon to 44 to 131 ug/L for catfish, perch and goldfish. Lindane is believed to cause birth defects in amphibians (Johnson and Finley, 1980). Treatment and Remediation of Organochlorine InsecticidesThree general techniques for treatment and remediation of organochlorine insecticides include:
Removal efficiency: >98%
Removal efficiency: 99% Removal efficiency (chlordane): 75-96%
Removal efficiency (DDT): >99% Discussion of EXAMS ResultsOrganochlorine insecticides were chosen for this investigation because of their environmental persistence and potency as toxins. As depicted in Table 1, each compound is physically and chemically unique, although they are equally representative of organochlorine chemicals. Characteristic of most organochlorines is a propensity for sorption to organic matter, and low water solubility, and high persistence (i.e., low reactivity) in nature when compared to other environmental contaminants. Despite their similarities as members of this class of compounds, their specific chemical and physical differences from one another produce notable variations with respect to environmental fate. These differences were readily observed using the EXAMS model and are discussed below. The modeled system was a freshwater pond, which received a stream load of DDT, chlordane, and lindane in aqueous phase at a rate of 0.0001 kg/hr. Other basic assumptions (e.g., water depth, surface area, sediment character) were built into the model. Environmental fate values for DDT, chlordane, and lindane as determined by the EXAMS model are included in the Appendix.Percent distribution of the chemicals in the pond environment indicated that lindane had greater affinity for dissolution in water (13% water/87% benthos) than DDT or chlordane (<1% water/>99% benthos) (Fig. 1). Nearly all of the DDT and chlordane partitioned to the benthos and biota. These differences can be attributed to very low water solubility of DDT (0.003 mg/L) and chlordane (0.1 mg/L) relative to lindane (7.3 mg/L). Noteworthy of this observation is lindane’s low molecular weight and smaller size compared to DDT and chlordane (Table 1). When considering chemical distribution in terms of concentration, the same trends were observed. DDT and chlordane partitioned primarily, and somewhat comparably, to organic matter, both in the form of benthic sediment (>30 mg/kg) and biota (³ 89 mg/kg). By contrast, lindane concentrations associated with organic matter were less (<1 mg/kg). Again, these observations can be attributed to the fact that Kow values for DDT and chlordane are three orders of magnitude greater than that of lindane (Table 1). If the three compounds are compared with respect to persistence in the environment, DDT was the most recalcitrant compound studied. Lindane was the least persistent and chlordane was intermediate. According to the EXAMS model, >70% of DDT would be lost from sediment in 196 yr. and from the water column in 72 yr. By comparison, lindane would be lost in only 33 mo. and 312 d from the respective compartments. Chlordane would persist similarly to DDT: 104 yr. in sediment and 39 yr. in water before 70% loss. Processes by which these organochlorine compounds are removed from the pond environment are primarily through surface water-borne export and volatilization (Fig. 2). Chlordane had the greatest volatilization rate (0.4 kg/yr.) with nearly proportional volumes exiting the system through volatilization and surface water-borne export (43% and 57%, respectively). By contrast, lindane and DDT were an order of magnitude less volatile, with loss from the pond system primarily through surface water-borne export (³ 90%) (Fig. 2). The EXAMS model effectively depicted the environmental fate of DDT, chlordane, and lindane in the pond ecosystem. Based upon fundamental principles regarding chemical/physical properties of the compounds, the model supported the expectations of environmental fate. For example, DDT, with the lowest water solubility and greatest Kow of the three compounds, partitioned the most to the sediment and biota. By contrast, lindane, with the greatest water solubility, possessed the greatest rate of surface water-borne export. In addition to providing general trends of environmental fate, the EXAMS model is useful for quantifying fate mechanisms with reasonable approximation. ReferencesAgency for Toxic Substances and Diseases Registry (ATSDR). 1994a. Toxicological Profile for 4,4'-DDT, 4,4'-DDE, 4, 4'-DDD (Update), U.S. Department of Human and Health Services, Public Health Service, Atlanta, GA. Agency for Toxic Substances and Disease Registry (ASTDR). 1994b. Toxicological Profile for Chlordane (Update). U.S. Department of Human and Health Services, Public Health Service, Atlanta, GA. Augustijn-Beckers, P.W.M., Hornsby, A.G. and Wauchope, R.D. 1994. SCS/ARS/CES Pesticide Properties Database for Environmental Decisionmaking II, Additional Properties Reviews of Environmental Contamination and Toxicology, Vol. 137. Brown, A.W.A. 1978. Ecology of Pesticides, John Wiley and Sons, New York, NY. Dearth, M.A. and Hites, R.A. 1990. Highly Chlorinated Dimethanofluorenes in Technical Chlordane and in Human Adipose Tissue. J.Am. Soc. Mass. Spectrum. 1:99-103. Hudson, R.H., Tucker, R.K. and Haegele, K. 1984. Handbook of Acute Toxicity of Pesticides to Wildlife. Resource Publication 153. U.S. Dept. of Interior, Fish and Wildlife Service, Washington, DC. International Organization of Consumers Unions. 1986. The Pesticide Handbook, Profiles for Action. Johnson, W.W. and Finley, M.T. 1980. Handbook of Acute Toxicity of Chemicals to Fish and Aquatic Invertebrates, Resource Publication 137. U.S. Dept. of Interior, Fish and Wildlife Service. Washington, DC. Jorgensen, S.E., Jorgensen, L.A. and Nielsen, S.N. 1991. Handbook of Ecological Parameters and Ecotoxicology. Elsevier. Amsterdam, Netherlands. Kirk-Othmer. 1995. Insect Control Technology. In: Encyclopedia of Chemical Technology. Ed.: J.I. Kroschwitz . A Wiley-Interscience Publication. New York. Matsumura, F. 1985. Toxicology of Insecticides. Second Edition. Plenum Press, New York, NY. Matsunaga, K., Imanaka, M., Kenonotsu, K., Oda, J., Hino, S., Kadota, M., Fujuwara, H., and Mori, T.. 1991. Superoxide-Radical- Induced Degradation of PCBs and Chlordanes at Low Temperature. Bulletin of Environmental Contamination and Toxicology. 46:292-299. Mackay, D., Shiu, W., and Ma, K. 1997. Illustrated Handbook of Physical –Chemical Properties and Environmental Fate for Organic Chemicals, Volume V, Pesticide Chemicals. Lewis Publishers, Boca Raton, FL. Meister, R.T. (ed.) 1992. Farm Chemicals Handbook '92, Meister Publishing Co., Willoughby, OH. Modell, M. 1985. Processing Methods for the Oxidation of Organics in Supercritical Water, U.S. Patent 4,543,190. In: LaGrega, M., Buckingham, P. and Evans, J. (eds.) Hazardous Waste Management, McGraw-Hill, New York, NY. Review of Chlordane. 1988. Reviews of Environmental Contamination and Toxicology. 104:48-62. Royal Society of Chemistry. 1991 (as updated). The Agrochemicals Handbook, Royal Society of Chemistry Information Services, Cambridge, UK. Sabatini, D.A., Smith, J.W., and Moore, L.W. 1990. Treatment of Chlordane-contaminated Water by the Activated Rotating Biological Contractor. Journal of Environmental Quality. 19:334-338. Smith, A.G. 1991. Chlorinated hydrocarbon insecticides. In: Handbook of Pesticide Toxicology, Volume 2, Classes of Pesticides. Hayes, W.J. and Laws, E.R. (eds.), Academic Press, San Diego, CA. Troxler, W.L., Goh, S.K., and Dick, L.W.R. 1993. Treatment of Pesticide-contaminated Soil with Thermal Desorption Technologies. Air and Waste 43:1610-1619. U.S. Environmental Protection Agency (EPA). 1990. National Pesticide Survey: Chlordane. Offices of Water and Of Pesticides and Toxic Substances, U.S. EPA, Washington, DC. U.S. Environmental Protection Agency. 1989. Environmental Fate and Effects Division, Pesticide Environmental Fate One Line Summary: DDT (p, p'). Washington, DC. United States Army Center for Health Promotion and Preventive Medicine Entomological Sciences Program (U.S. Army). 1997. Pest Management Manual, December, 1997. Van Ert, M. and Sullivan, J.B. 1992. Organochlorine Pesticides. In: Sullivan, J.B. and Krieger, G.R. (eds.) Hazardous Materials Toxicology, Clinical Principles of Environmental Health. Williams & Wilkins, Baltimore, MD. World Health Organization (WHO). 1989. Environmental health Criteria 83, DDT and its DerivativesÑEnvironmental Effects. World Health Organization, Geneva. 
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