Chemical Structure Of Lindane Biology Essay

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Lindane is an organochlorine chemical that is widely used as agricultural insecticide and also as pharmaceutical second-line1 treatment for scabies and lice. It is also known by names; gamma-Hexachlorocyclehexane(γ-HCH), Benzene haxachloride (BHC)2, Gammaxene and Gammalin. Agricultural-grade lindane products have accounted for more than 99% of all lindane uses. Less than 1% of lindane has been used in the form of medications pharmaceutical-grade for the treatment of human disease like scabies, head lice, crab lice. [1]

Chemical Structure of Lindane

Lindane is made up of at least 99% of gamma isomer of HCH, hence the name γ-HCH. Technical HCH can include varying proportions of alpha, betha, delta and epsilon HCH isomers which have been shown to have serious short and long term health effects. Virtually all the insecticidal properties resided in γ-HCH. 

Agricultural-grade lindane products have accounted for more than 99% of all lindane uses. Less than 1% of lindane has been used in the form of medications pharmaceutical-grade for the treatment of human disease like scabies, head lice, crab lice.[1]

Lindane is classified as moderately hazardous by World Health Organization and its trade is restricted and regulated. Presently its use is banned in more than 50 countries worldwide. Its use is still persistent in big countries like United States, Canada for medical treatment though its use in agriculture is completely banned except for the treatment of pre-planting seeds for 6 crops- barley, corn, oats, rye, sorghum and wheat[1].

Lindane is prescribed only when first-line are failed or cannot be tolerated

According to IUPAC rules, the designation "benzene hexachloride" is incorrect. But it is still widely used in the name of BHC and it is approved by the ISO [3].

Lindane is found in air, water and soil throughout the world. It is highly persistent and travels long distances via atmosphere and oceanic currents. In fact, lindane with its isomers is the most abundant pesticide in Arctic air and water [2].

Physical and Chemical Properties:

Lindane is a white solid that may evaporate into the air as a colorless vapor with a slightly musty odor.

The characteristic smell of technical HCH is attributed to the impurities, particularly heptachlorocyclohexane

It is stable to air, light, heat, carbon dioxide, and strong acids.

Dehydrochlorination of the compound may occur in the presence of alkali, or on prolonged heating forming trichlorobenzens and hydrochloric acid.

Rapid degradation (dechlorination) of lindane occurs on exposure to Ultraviolet radiation forming gamma pentachlorocyclohexenes (PCCH) and tetrachlorocyclohexens.

The half-life for the environmental degradation of lindane under humid or submerged conditions, and field conditions varies from few days to 3 years depending on the factors such as soil type, climate, and depth of application.

Lindane is incompatible with strong bases and powdered metals such as iron, zinc, and aluminum. It is also incompatible with oxidizing agents and can undergo oxidation when in contact with ozone [3].

Other properties of the compound are summarized below:

Common Name



CAS Chemical Name


1 alpha, 2 alpha, 3 beta, 4 alpha, 5 alpha, 6 beta, hexachloro Cyclohexane

Chemical Family


Organochlorine Insecticide

Empirical Formula



Relative molecular mass



C.A.S. No.





1.85 g/ml at 20oC

Melting Point


112 to 113oC

Vapor Pressure


5.6 mPa at 20oC

Explosion Hazard



Flash Point



Solubility in water


7.3 mg/l at 25oC


Since early 1950s, lindane has been used as an agricultural insecticide. It has been used in seed treatment, soil treatment, foliar applications, treatment of forests, timber, stored materials or products, and against ectoparasites on animals and in public health.

It has been used as popular household fumigant, effective against flies and cockroaches until it was found to be hazardous to people and pets. The mode of action of lindane on insects is generally as a stomach poison with some fumigant action that it kills insects that ingest it or inhale its vapor.

Lindane was introduced as a pediculicide3 and scabicide4 in 1952 by Reed and Carnrick. Other commonly used brand names are Thionex (in US) and Hexit, PMS Lindane (in Canada).

It is also available as a prescription to treat scabies infestation(available as lotion cream), and to treat head and body lice (available in the form of shampoo). Because of the potential risks associated with lindane, its use is no longer recommended as the first-line drug therapy for treating scabies and body lice.

It is available as a suspension, emulsifiable concentrate, fumigant, seed treatment, wettable and dustable powder, and ultra-low-volume (ULV) liquid.

Though lindane has many applications it has been banned in many countries due to its adverse effects.


Environmental Effects: It contaminates drinking water sources. Lindane in water can be determined by extraction with petroleum ether followed by gas chromatography.

3 Pediculicide- Medication to treat lice and Scabies

4 Scabicide- Medication to treat Scabies

The limit of detection is 0.01 μg/litre. Lindane is also leached into surface waters and even into ground water.Lindane is highly volatile, and when applied to field crops in particular, a high proportion (up to 90%) of the pesticide enters the atmosphere and is later deposited by rain. In common with other organochlorine pesticides lindane is fat soluble and this contributes to its tendency to bioaccumulate through food chains. Residues have been detected in the kidneys, livers and adipose tissue of a wide variety of wild animals and birds. It is highly toxic to aquatic invertebrates and fish.The production of lindane generates large amounts of waste hexachlorocyclohexane isomers, and it is estimated that every ton of lindane manufactured produces about 9 tons of toxic waste. Lindane in soil can leach to surface and even ground water and can bioaccumulate in the food chain. Over time, lindane is broken down in soil, sediment and water into less harmful substances by algae, fungi and bacteria; however, the process is relatively slow and dependent on ambient environmental conditions.

Effects on Human beings: Daily intake of HCH isomers in adult diets in the USA in 1981-1982 was reported to be 10 ng/kg of body weight for total HCH (8 ng of α-HCH and 2 ng of γ-HCH per kg of body weight) (ATSDR, 1989). In the Netherlands, the daily intake from food has been calculated to be 1 μg for the α-, β- and γ-isomers, or approximately 15 ng/kg of body weight (Slooff & Matthijsen, 1988; IPCS, 1991). Intake from air may be considerable for people living in houses treated for pest control purposes. Symptomatology included: nausea, restlessness, headache, vomiting, tremor, ataxia, tonic-clonic convulsions, and/or changes in the EEG pattern. These effects were reversible following cessation of exposure and/or symptomatic treatment. In spite of the extensive use of lindane over 40 years, only very few cases of occupational poisoning have been reported. Even in workers exposed for long periods in both the manufacture and application of lindane, only an increase in the activity of drug-metabolizing enzymes of the liver has been occasionally found [3]. It was concluded from a few acute and short-term studies on humans that a dose level of approximately 1.0 mg/Kg body weight does not induce poisoning, but a dose level of 15-17 mg/Kg body weight will result in severe toxic symptoms. Approximately 10% of a dermally applied dose is absorbed through the human skin, but more is absorbed when the skin is damaged.

Lindane is distributed all over the world and can be detected in the air, water, soil/sediment, aquatic and terrestrial organisms, and in food. The concentrations in these different compartments are usually low and are gradually decreasing. Thus, though human exposure occurs via the daily food intake and lindane has been found in human blood, adipose tissue, and breast milk, the figures are gradually decreasing.

Current Regulations:

The International Agency for Research on Cancer (IARC) evaluated the hexachlorocyclohexanes in 1987 and concluded that, for the technical grade and the alpha-isomer, there is sufficient evidence for carcinogenicity for animals; evidence is limited for the beta- and gamma-isomers.

WHO (1990) classified technical lindane as "moderately hazardous" in normal use (on the basis of an LD50 of 88 mg/kg).

WHO/FAO (1975) issued a data sheet on lindane (No. 12), dealing with labeling, safe handling, transport, storage, disposal, decontamination, training, and medical supervision of workers,

first-aid, and medical treatment.

Maximum residue limits (MRLs) have been recommended by the FAO/ WHO Codex Committee for more than 35 commodities, ranging from 0.05 mg/kg on potatoes to 3 mg/kg on strawberries. A level of 0.5 mg/kg was recommended for most fruit and vegetables.

The International Agency for Research in Cancer (IARC) and the U.S. EPA classify lindane as a possible human carcinogen.

In Japan, all uses of HCH and lindane were prohibited in 1971. The main reason was the environmental pollution with alpha-HCH and ß-HCH that resulted from the previous extensive use of technical HCH. Agricultural uses of technical HCH have been prohibited in most countries, because of environmental pollution with alpha-HCH and ß-HCH.

Several techniques have been proposed for the destruction of lindane, including thermal treatment, molecular distillation and biocatalysis approaches. But since the costs involved in these processes are very high, these methods are not economically feasible for destruction of lindane. The present work focuses on the development of an economical method for destruction of Lindane (g-HCH) into products which are non toxic in nature. The selected method catalytically converts Lindane into non toxic products using nano iron oxide (Fe2O3) as a catalyst. To test this technology an experimental system was designed and preliminary conditions were chosen based on results of study where different catalyst and experimental conditions were investigated.

In the present study three set of experiments were conducted for destruction of lindane. In the first set, experiments were conducted using micro iron oxide particles loaded catalyst and second set of experiments were conducted using nano iron oxide particles loaded catalyst. In this two set of experiments lindane is mixed with acetone in proportion of 25 gm/ml and fed into reactor tube with the help of syringe infusion pump as micro droplets. In the third set of experiments lindane in vapor form fed into the reactor. Iron nano particles were chosen because they have already been used successfully to dechlorinate many chlorinated organic pollutants such as chloroform, carbon tetra chloride and PCBs.

In this process lindane was passed over nano iron oxide catalyst and it gets adsorbed on the surface of the metal. Iron oxide then reduces chlorinated compound to its dechlorinated form. The usage of nano iron oxide catalyst and maintaining low temperature (3000 C) for the destruction of lindane makes the process economically viable. The effectiveness of nano iron oxide catalyst decreases as more amount of lindane was fed over the catalyst. In the current work different tests were performed for restoration of nano iron oxide catalyst and a technique was found to restore the catalyst which is economically feasible.