Lindane
Encyclopedia
Lindane, also known as gamma-hexachlorocyclohexane, (γ-HCH), gammaxene, Gammallin and erroneously known as benzene hexachloride (BHC), is an organochlorine chemical variant of hexachlorocyclohexane
that has been used both as an agricultural insecticide
and as a pharmaceutical treatment for lice
and scabies
.
Lindane is a neurotoxin
that interferes with GABA
neurotransmitter
function by interacting with the GABAA receptor-chloride channel complex at the picrotoxin
binding site. In humans, lindane affects the nervous system
, liver
and kidneys, and may be a carcinogen
. It is unclear whether lindane is an endocrine disruptor
.
The World Health Organization
classifies lindane as "Moderately Hazardous," and its international trade is restricted and regulated under the Rotterdam Convention
on Prior Informed Consent. In 2009 the production and agricultural use of lindane was banned under the Stockholm Convention
on persistent organic pollutants. A specific exemption to that ban allows it to continue to be used as a second-line pharmaceutical treatment for lice and scabies.
, but its pesticidal action was discovered only in 1942, after which lindane production, by Imperial Chemical Industries
Ltd (ICI), and use started up in the United Kingdom. It has been used to treat food crops and to forestry products, as a seed treatment
, a soil treatment, and to treat livestock and pets. It has also been used as pharmaceutical treatment for lice and scabies, formulated as a shampoo or lotion. It is estimated that between 1950 and 2000, around 600,000 tonnes of lindane were produced globally, and the vast majority of which was used in agriculture. It has been manufactured by several countries, including the United States
, China
, Brazil
, and several European countries
, but as of 2007 only India
and possibly Russia
are still producing it.
By November 2006, the use of lindane had been banned in 52 countries and restricted in 33 others. Seventeen countries, including the US and Canada, allowed either limited agricultural or pharmaceutical use. In 2009, an international ban on the use of lindane in agriculture was implemented under the Stockholm Convention on Persistent Organic Pollutants
. A specific exemption allows for it to continue to be used in second-line treatments for the head lice and scabies for 5 more years. The production of the lindane isomers α- and β-hexachlorocyclohexane was also banned. Although the US has not ratified the Convention, it has similarly banned agricultural uses while still allowing its use a second-line lice and scabies treatment.
to Morton Grove Pharmaceuticals, the sole U.S. manufacturer of lindane products,Sciele Pharma Completes Acquisition of Alliant Pharmaceuticals. Press Release; June 12, 2007. http://phx.corporate-ir.net/phoenix.zhtml?c=120763&p=irol-newsArticle&ID=1014610&highlight requesting that the company correct misleading information on two of its lindane websites. The letter said, in part, that the materials "are misleading in that they omit and/or minimize the most serious and important risk information associated with the use of Lindane Shampoo, particularly in pediatric patients; include a misleading dosing claim; and overstate the efficacy of Lindane Shampoo."
The State of California
banned the pharmaceutical lindane, effective 2002, and the Michigan House of Representatives passed a bill in 2009 to restrict its use to doctors' offices. A recent analysis of the California ban concluded that a majority of pediatricians had not experienced problems treating lice or scabies since that ban took effect. The study also documented a marked decrease in lindane wastewater contamination and a dramatic decline in lindane poisoning incidents reported to Poison Control Centers. The authors concluded that, "The California experience suggests elimination of pharmaceutical lindane produced environmental benefits, was associated with a reduction in reported unintentional exposures and did not adversely affect head lice and scabies treatment."
Exposure to large amounts of lindane can harm the nervous system
, producing a range of symptoms from headache and dizziness to seizures, convulsions and more rarely death. Lindane has not been shown to affect the immune system
in humans and, it is not considered to be genotoxic. Prenatal exposure to β-HCH, an isomer
of lindane and production byproduct, has been associated with altered thyroid hormone levels and could affect brain development.
(IARC) classified lindane as a group 2B "possible" human carcinogen, and in 2001 the EPA concluded there was “suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential.” The U.S. Department of Health and Human Services determined that all isomers of hexachlorocyclohexane, including lindane, "may reasonably be anticipated to cause cancer in humans," and in 1999, the EPA characterized the evidence carcinogenicity for lindane as "suggestive ... of carcinogenicity, but not sufficient to assess human carcinogenic potential." Lindane and its isomers have also been on California's Proposition 65 list of known carcinogens since 1989. In contrast, the World Health Organization
concluded in 2004 that “lindane is not likely to pose a carcinogenic risk to humans.”
s, and, in rare instances, death. The most common side effects are burning sensations, itching, dryness and rash. While serious effects are rare and have most often resulted from misuse, adverse reactions have occurred when used properly. The FDA therefore requires a so-called black box warning
on lindane products, which explains the risks of lindane products and its proper use.
The black box warning emphasizes that lindane should not be used on premature infants and individuals with known uncontrolled seizure disorders, and should be used with caution in infants, children, the elderly, and individuals with other skin conditions (e.g., dermatitis
, psoriasis
) and people who weigh less than 110 lbs (50 kg) as they may be at risk of serious neurotoxicity.
: it is relatively long-lived in the environment, it is transported long distances by natural processes like global distillation
, and it can bioaccumulate in food chain
s, though it is rapidly eliminated when exposure is discontinued.
The production and agricultural use of lindane are the primary causes of environmental contamination, and levels of lindane in the environment have been decreasing in the U.S., consistent with decreasing agricultural usage patterns. 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." Modern manufacturing standards for lindane involve the treatment and conversion of waste isomers to less toxic molecules, a process known as "cracking."
When lindane is used in agriculture, an estimated 12-30% of it volatilizes into the atmosphere, where it is subject to long-range transport
and can be deposited by rainfall. Lindane in soil can leach to surface and even ground water and can bioaccumulate in the food chain. However, biotransformation and elimination are relatively rapid when exposure is discontinued. Most exposure of the general population to lindane has resulted from agricultural uses and the intake of foods, such as produce, meats and milk, produced from treated agricultural commodities. Human exposure has decreased significantly since the cancellation of agricultural uses in 2006. Even so, the CDC published in 2005 its Third National Report on Human Exposures to Environmental Chemicals, which found no detectable amounts of lindane in human blood taken from a random sampling of about 5,000 people in the US as part of the NHANES study (National Health and Nutrition Examination Survey at: http://www.cdc.gov/nchs/nhanes/about_nhanes.htm ). The lack of detection of lindane in this large human "biomonitoring" study likely reflects the increasingly limited agricultural uses of lindane over the last two decades. The cancellation of agricultural uses in the U.S. will further reduce the amount of lindane introduced into the environment by more than 99%.
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. The ecological impact of lindane’s environmental persistence continues to be debated.
The US EPA determined in 2002 that the Agency does not believe that lindane contaminates drinking water in excess of levels considered safe. U.S. Geologic Survey teams concluded the same in 1999 and 2000. With regard to lindane medications, the EPA conducted "down-the-drain" estimates of the amount of lindane reaching public water supplies and concluded that lindane levels from pharmaceutical sources were "extremely low" and not of concern.
Note that the EPA has set the maximum contaminant level or "MCL" for lindane allowed in public water supplies and considered safe for drinking at 200 parts per trillion (ppt). By comparison, the state of California imposes a lower MCL for lindane of 19 ppt. However, the California standard is based on a dated 1988 national water criterion that was subsequently revised by the EPA in 2003 to 980 ppt. The EPA stated that the change resulted from "significant scientific advances made in the last two decades particularly in the areas of cancer and noncancer risk assessments." While the EPA considered raising the MCL standard for lindane to 980 ppt at that time, the change was never implemented because states had little difficultly in maintaining lindane levels below the 200 ppt MCL limit already in place. Today, the legally enforceable MCL standard for lindane is 200 ppt while the national water criterion for lindane is 980 ppt.
("γ-HCH"). In addition to the issue of lindane pollution are concerns related to the other isomers of HCH, namely alpha-HCH and beta-HCH, which are notably more toxic than lindane, lack its insecticidal properties, and are byproducts of lindane production. In the 1940s and 1950s lindane producers stockpiled these isomers in open heaps, which led to ground and water contamination. The International HCH and Pesticide Forum has since been established to bring together experts to address the clean-up and containment of these sites. Modern manufacturing standards for lindane involve the treatment and conversion of waste isomers to less toxic industrial chemicals, a process known as "cracking
." Today, only a few production plants remain active worldwide to accommodate public health uses of lindane and declining agricultural needs. Lindane has not been manufactured in the U.S. since the mid-1970s but continues to be imported.
Hexachlorocyclohexane
Hexachlorocyclohexane or 666 is a six chlorine substituted cyclohexane, a polyhalogenated compound. It comes in many forms. Some are pesticides.Common forms are:* α-HCH , or α-BCH, alpha-Hexachlorocyclohexane...
that has been used both as an agricultural insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
and as a pharmaceutical treatment for lice
Pediculosis
Pediculosis is an infestation of lice — blood-feeding ectoparasitic insects of the order Phthiraptera. The condition can occur in almost any species of warm-blooded animal , including humans...
and scabies
Scabies
Scabies , known colloquially as the seven-year itch, is a contagious skin infection that occurs among humans and other animals. It is caused by a tiny and usually not directly visible parasite, the mite Sarcoptes scabiei, which burrows under the host's skin, causing intense allergic itching...
.
Lindane is a neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
that interferes with GABA
Gabâ
Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...
neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
function by interacting with the GABAA receptor-chloride channel complex at the picrotoxin
Picrotoxin
Picrotoxin, also known as cocculin, is a poisonous crystalline plant compound, first isolated by Pierre Boullay in 1812. The name "picrotoxin" is a combination of the Greek words "picros" and "toxicon" ....
binding site. In humans, lindane affects the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and kidneys, and may be a carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
. It is unclear whether lindane is an endocrine disruptor
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...
.
The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
classifies lindane as "Moderately Hazardous," and its international trade is restricted and regulated under the Rotterdam Convention
Rotterdam Convention
The Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade, more commonly known simply as the ', is a multilateral treaty to promote shared responsibilities in relation to importation of hazardous chemicals...
on Prior Informed Consent. In 2009 the production and agricultural use of lindane was banned under the Stockholm Convention
Stockholm Convention
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...
on persistent organic pollutants. A specific exemption to that ban allows it to continue to be used as a second-line pharmaceutical treatment for lice and scabies.
History and use
The chemical was originally synthesised in 1825 by FaradayMichael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
, but its pesticidal action was discovered only in 1942, after which lindane production, by Imperial Chemical Industries
Imperial Chemical Industries
Imperial Chemical Industries was a British chemical company, taken over by AkzoNobel, a Dutch conglomerate, one of the largest chemical producers in the world. In its heyday, ICI was the largest manufacturing company in the British Empire, and commonly regarded as a "bellwether of the British...
Ltd (ICI), and use started up in the United Kingdom. It has been used to treat food crops and to forestry products, as a seed treatment
Seed treatment
In agriculture, a seed treatment or seed dressing is a chemical, typically antimicrobial or fungidal, with which seeds are treated prior to planting...
, a soil treatment, and to treat livestock and pets. It has also been used as pharmaceutical treatment for lice and scabies, formulated as a shampoo or lotion. It is estimated that between 1950 and 2000, around 600,000 tonnes of lindane were produced globally, and the vast majority of which was used in agriculture. It has been manufactured by several countries, including the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, and several European countries
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, but as of 2007 only India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and possibly Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
are still producing it.
By November 2006, the use of lindane had been banned in 52 countries and restricted in 33 others. Seventeen countries, including the US and Canada, allowed either limited agricultural or pharmaceutical use. In 2009, an international ban on the use of lindane in agriculture was implemented under the Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...
. A specific exemption allows for it to continue to be used in second-line treatments for the head lice and scabies for 5 more years. The production of the lindane isomers α- and β-hexachlorocyclohexane was also banned. Although the US has not ratified the Convention, it has similarly banned agricultural uses while still allowing its use a second-line lice and scabies treatment.
United States
In the US, lindane pesticide products were regulated by the U.S. Environmental Protection Agency (EPA), while lindane medications are regulated by the Food and Drug Administration (FDA). It was registered as an agricultural insecticide in the 1940s and as pharmaceutical in 1951. The EPA gradually began restricting its agricultural use in the 1970s due to concerns over its effects on human health and the environment. By 2002, its use was limited to seed treatments for just 6 crops, and in 2007 these last uses were canceled.Pharmaceutical uses
Lindane medications continue to be available in the US, though since 1995 they have been designated "second-line" treatments, meaning they can only be prescribed when other "first-line" treatments have failed or cannot be used. In December 2007, the FDA sent a Warning LetterFDA Warning Letter
The United States Food and Drug Adminstration defines a Warning Letter as "...a correspondence that notifies regulated industry about violations that FDA has documented during its inspections or investigations...
to Morton Grove Pharmaceuticals, the sole U.S. manufacturer of lindane products,Sciele Pharma Completes Acquisition of Alliant Pharmaceuticals. Press Release; June 12, 2007. http://phx.corporate-ir.net/phoenix.zhtml?c=120763&p=irol-newsArticle&ID=1014610&highlight requesting that the company correct misleading information on two of its lindane websites. The letter said, in part, that the materials "are misleading in that they omit and/or minimize the most serious and important risk information associated with the use of Lindane Shampoo, particularly in pediatric patients; include a misleading dosing claim; and overstate the efficacy of Lindane Shampoo."
The State of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
banned the pharmaceutical lindane, effective 2002, and the Michigan House of Representatives passed a bill in 2009 to restrict its use to doctors' offices. A recent analysis of the California ban concluded that a majority of pediatricians had not experienced problems treating lice or scabies since that ban took effect. The study also documented a marked decrease in lindane wastewater contamination and a dramatic decline in lindane poisoning incidents reported to Poison Control Centers. The authors concluded that, "The California experience suggests elimination of pharmaceutical lindane produced environmental benefits, was associated with a reduction in reported unintentional exposures and did not adversely affect head lice and scabies treatment."
Morton Grove lawsuit
In 2006 Morton Grove Pharmaceuticals, the sole US manufacturer of lindane pharmaceuticals, sued the National Pediculosis Association, the Michigan Ecology Center, and two physicians, alleging that they disseminated defamatory materials regarding lindane and other charges. Morton Grove alleged more than $9.3 million in damages. The defendants considered the legal action to be SLAPP suit and settled in 2008. The settlement did not require them to admit liability or make any payments to Morton Grove, but the Ecology Center did agree to clarify 7 of the statements it had published in its lindane factsheet.Human health effects
The EPA and WHO both classify lindane as "moderately" acutely toxic. It has an oral of 88 mg/kg in rats and a dermal LD50 of 1000 mg/kg. Most of the adverse human health effects reported for lindane have been related to agricultural uses and chronic, occupational exposure of seed treatment workers.Exposure to large amounts of lindane can harm the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
, producing a range of symptoms from headache and dizziness to seizures, convulsions and more rarely death. Lindane has not been shown to affect the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
in humans and, it is not considered to be genotoxic. Prenatal exposure to β-HCH, an isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
of lindane and production byproduct, has been associated with altered thyroid hormone levels and could affect brain development.
Cancer risk
Based primarily on evidence from animal studies, most evaluations of lindane have concluded that it may possibly cause cancer. In 1987, the International Agency for Research on CancerInternational Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....
(IARC) classified lindane as a group 2B "possible" human carcinogen, and in 2001 the EPA concluded there was “suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential.” The U.S. Department of Health and Human Services determined that all isomers of hexachlorocyclohexane, including lindane, "may reasonably be anticipated to cause cancer in humans," and in 1999, the EPA characterized the evidence carcinogenicity for lindane as "suggestive ... of carcinogenicity, but not sufficient to assess human carcinogenic potential." Lindane and its isomers have also been on California's Proposition 65 list of known carcinogens since 1989. In contrast, the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
concluded in 2004 that “lindane is not likely to pose a carcinogenic risk to humans.”
Adverse reactions to lindane pharmaceuticals
A variety of adverse reactions to lindane pharmaceuticals have been reported, ranging from skin irritation to seizureSeizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s, and, in rare instances, death. The most common side effects are burning sensations, itching, dryness and rash. While serious effects are rare and have most often resulted from misuse, adverse reactions have occurred when used properly. The FDA therefore requires a so-called black box warning
Black box warning
In the United States, a black box warning is a type of warning that appears on the package insert for prescription drugs that may cause serious adverse effects...
on lindane products, which explains the risks of lindane products and its proper use.
The black box warning emphasizes that lindane should not be used on premature infants and individuals with known uncontrolled seizure disorders, and should be used with caution in infants, children, the elderly, and individuals with other skin conditions (e.g., dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
, psoriasis
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
) and people who weigh less than 110 lbs (50 kg) as they may be at risk of serious neurotoxicity.
Environmental contamination
Lindane is a persistent organic pollutantPersistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...
: it is relatively long-lived in the environment, it is transported long distances by natural processes like global distillation
Global distillation
Global distillation or the grasshopper effect is the geochemical process by which certain chemicals, most notably persistent organic pollutants , are transported from warmer to colder regions of the Earth, particularly the Poles and mountain tops...
, and it can bioaccumulate in food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
s, though it is rapidly eliminated when exposure is discontinued.
The production and agricultural use of lindane are the primary causes of environmental contamination, and levels of lindane in the environment have been decreasing in the U.S., consistent with decreasing agricultural usage patterns. 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." Modern manufacturing standards for lindane involve the treatment and conversion of waste isomers to less toxic molecules, a process known as "cracking."
When lindane is used in agriculture, an estimated 12-30% of it volatilizes into the atmosphere, where it is subject to long-range transport
Global distillation
Global distillation or the grasshopper effect is the geochemical process by which certain chemicals, most notably persistent organic pollutants , are transported from warmer to colder regions of the Earth, particularly the Poles and mountain tops...
and can be deposited by rainfall. Lindane in soil can leach to surface and even ground water and can bioaccumulate in the food chain. However, biotransformation and elimination are relatively rapid when exposure is discontinued. Most exposure of the general population to lindane has resulted from agricultural uses and the intake of foods, such as produce, meats and milk, produced from treated agricultural commodities. Human exposure has decreased significantly since the cancellation of agricultural uses in 2006. Even so, the CDC published in 2005 its Third National Report on Human Exposures to Environmental Chemicals, which found no detectable amounts of lindane in human blood taken from a random sampling of about 5,000 people in the US as part of the NHANES study (National Health and Nutrition Examination Survey at: http://www.cdc.gov/nchs/nhanes/about_nhanes.htm ). The lack of detection of lindane in this large human "biomonitoring" study likely reflects the increasingly limited agricultural uses of lindane over the last two decades. The cancellation of agricultural uses in the U.S. will further reduce the amount of lindane introduced into the environment by more than 99%.
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. The ecological impact of lindane’s environmental persistence continues to be debated.
The US EPA determined in 2002 that the Agency does not believe that lindane contaminates drinking water in excess of levels considered safe. U.S. Geologic Survey teams concluded the same in 1999 and 2000. With regard to lindane medications, the EPA conducted "down-the-drain" estimates of the amount of lindane reaching public water supplies and concluded that lindane levels from pharmaceutical sources were "extremely low" and not of concern.
Note that the EPA has set the maximum contaminant level or "MCL" for lindane allowed in public water supplies and considered safe for drinking at 200 parts per trillion (ppt). By comparison, the state of California imposes a lower MCL for lindane of 19 ppt. However, the California standard is based on a dated 1988 national water criterion that was subsequently revised by the EPA in 2003 to 980 ppt. The EPA stated that the change resulted from "significant scientific advances made in the last two decades particularly in the areas of cancer and noncancer risk assessments." While the EPA considered raising the MCL standard for lindane to 980 ppt at that time, the change was never implemented because states had little difficultly in maintaining lindane levels below the 200 ppt MCL limit already in place. Today, the legally enforceable MCL standard for lindane is 200 ppt while the national water criterion for lindane is 980 ppt.
Isomers
Lindane is the gamma isomer of hexachlorocyclohexaneHexachlorocyclohexane
Hexachlorocyclohexane or 666 is a six chlorine substituted cyclohexane, a polyhalogenated compound. It comes in many forms. Some are pesticides.Common forms are:* α-HCH , or α-BCH, alpha-Hexachlorocyclohexane...
("γ-HCH"). In addition to the issue of lindane pollution are concerns related to the other isomers of HCH, namely alpha-HCH and beta-HCH, which are notably more toxic than lindane, lack its insecticidal properties, and are byproducts of lindane production. In the 1940s and 1950s lindane producers stockpiled these isomers in open heaps, which led to ground and water contamination. The International HCH and Pesticide Forum has since been established to bring together experts to address the clean-up and containment of these sites. Modern manufacturing standards for lindane involve the treatment and conversion of waste isomers to less toxic industrial chemicals, a process known as "cracking
Cracking (chemistry)
In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products...
." Today, only a few production plants remain active worldwide to accommodate public health uses of lindane and declining agricultural needs. Lindane has not been manufactured in the U.S. since the mid-1970s but continues to be imported.
Government and organizations
- FDA Information on Lindane
- EPA Information on Lindane
- Gamma Hexachlorocyclohexane Fact Sheet
- Agency for Toxics and Disease Registry: Toxicological Profile for Hexachlorocyclohexane
- World Health Organization Background Document on Lindane for Drinking-Water Quality Guidelines
- PAN Pesticides Database: Lindane
- Lindane Chemistry and Uses
- World Health Organization: Lindane (EHC 124)
- "Lindane Facts" - Website run by Morton Grove Pharmaceuticals
- headlice.org - Website of the National Pediculosis Association
- Michigan Ecology Center website
- Morton Grove Pharmaceuticals homepage - US producer of Lindane Medications
- U.S. National Library of Medicine: Hazardous Substances Databank – Lindane
News stories and opinion articles
- "Mom and Pros Tackle Lice" - NPR story from 2006
- Pepsi and Coca-Cola - Lindane in drinks in India - news story from 2004
- India - Pesticides in Coke & Pepsi drinks - news story from 2003