Endosulfan is a pesticide belonging to the organochlorine group of pesticides, under the Cyclodiene subgroup. Introduced in the 1950's, it emerged as a leading chemical used against a broad spectrum of insects and mites in agriculture and allied sectors. It acts as contact and stomach poison and has a slight fumigant action1. It is used in vegetables, fruits, paddy, cotton, cashew, tea, coffee, and tobacco and timber crops. It is also used as a wood preservative and to control tse-tse flies and termites. It is not recommended for household use. Intentional misuse of endosulfan for killing fish, and snails has also been reported. Endosulfan was also reported as used deliberately as a method of removing unwanted fish from lakes before restoring.
Endosulfan was introduced at a time when environmental awareness and knowledge about the environmental fate and toxicology of such chemicals were low and not mandatory as per national laws. But now it is being detected as an important cause of pesticide poisoning in many countries.
In pure form endosulfan exists as colourless crystals. But the technical product is brownish crystals with slight odour of sulphur dioxide. Technically endosulfan is a mixture of two isomers – alphaendosulfan and beta-endosulfan in the ratio 7:3. Technical grade endosulfan contains 94% alphaendosulfan and beta-endosulfan and other related compounds like endosulfan alcohol, endosulfan ether and endosulfan sulfate. Endosulfan is only very slightly soluble in water, but it dissolves readily in xylene, chloroform, kerosene and most organic solvents and is a noncombustible solid. It is mixable with most fungicides and compatible with most pesticides.
What do international treaties say about endosulfan?
Endosulfan is widely considered to be a Persistent Organic Pollutant (POP) but was not included in the initial list targeted for phase out under the Stockholm Convention. Endosulfan was in the initial list of POPs being considered for world-wide elimination at the first meeting of experts in Vancouver, Canada (1994) jointly convened by governments of Canada and Philippines but was later removed from the list. However, endosulfan is listed as a POP in the Convention on Long-range Transboundary Air Pollution (LRTAP). Endosulfan is recognized as a Persistent Toxic Substance (PTS) by the UNEP.
What is the regulatory status of endosulfan in world nations?
Endosulfan has been in world-wide use since its introduction in the 1950's. It was considered a safer alternative to other organochlorine pesticides in many countries in all regions since the 1970's. But in the last two decades many countries have recognized the hazards of wide application of this pesticide and have banned or restricted its use. Countries which have banned include Singapore, Belize, Tonga, Syria, Germany, Sweden, Philippines, Netherlands, St. Lucia, Columbia, Cambodia, Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates, Sri Lanka and Pakistan. Restricted use is allowed in Australia, Bangladesh, Indonesia, Iran, japan, Korea, Kazakhstan, Lithuania, Thailand, Taiwan, Denmark, Serbia & Montenegro, Norway, Finland, Russia, Venezuela, Dominican Republic, Honduras, Panama, Iceland, Canada, the United States and the United Kingdom. It is one among the twenty one priority compounds identified by the UNEP-GEF in the Regional Based Assessment of Persistent Toxic Substances (PTS),2002. These reports have taken into account the magnitude of use, environmental levels and human and ecological effects of these compounds. In the Indian Ocean Region endosulfan is banned in 8 nations.
India is one of the major Indian Ocean rim nations, which has imposed no ban or restrictions on endosulfan. A ban on endosulfan exists in the South Indian state of Kerala (imposed through a Court Order), which came as a result of a public pressure following the poisoning of many villages due to aerial spraying of the chemical. Colombia and Cambodia are two countries where endosulfan is banned from use recently. In the Reports of the Regional Based Assessment of PTS of the UNEP- GEF, endosulfan has been rated depending on the level of concern in the respective region countries.
How might I be exposed to endosulfan ?
• By breathing air near where it has been sprayed.
• Drinking water contaminated directly or through run-offs.
• Being in contact with contaminated soil.
• Eating contaminated food.
• Smoking cigarettes made from endosulfan contaminated tobacco.
• Working at endosulfan production centers.
• Direct ingestion.
How does endosulfan affect human beings ?
Worldwide use of endosulfan increased with the ban/restriction in use of the more persistent organochlorine pesticides like DDT and endrin. Endosulfan is acutely toxic and has been implicated in many cases of poisoning and fatalities. It has been identified with a range of chronic effects, including cancer and impacts on hormonal systems, exhibiting similarities with its predecessors in the organochlorine class.
There is experimental evidence of adverse effects of endosulfan on the male reproductive system, delaying sexual maturity and interfering with the sex-hormone synthesis118. Endosulfan is a proven endocrine disruptor. It has potential to induce hypo thyroidism66. Long term health effects are not properly studied experimented or documented world wide.
Endosulfan exhibits estrogenic properties9, comparable to that of DDT. It competes for estradiol for binding to estrogen receptors, thereby inhibiting hormonal function. The estrogenic potential of endosulfan increases in the presence of other estrogenic organochlorines 110 .It induces proliferation of human breast estrogen sensitive MCF7 cells, (invitro) thereby increasing breast cancer risk. It harms the reproductive system by affecting semen quality, sperm count, spermatogonial cells, sperm morphology and other defects in male sex hormones.Endosulfan [is having] have the capacity to alter the genetic material particularly chromosomes in mammalian cultures. It is found to inhibit testicular androgen biosynthesis in lab animal experiments and exhibits significant risk in renal and testicular damage.
It may have adverse effects on central nervous system by inhibiting brain acetyl cholinesterase, causing uncontrolled discharge of acetyl choline. Endosulfan ingestion is known to affect the kidneys and liver. It inhibits leucocyte and macrophage migration (this is the inhibition of the natural immune system by disrupting anti-body protection) causing adverse effects on humoral and cell-mediated immune system. It is also a potential tumor promoter.
Many studies related to its acute and chronic toxicity in laboratory animals are available. Endosulfan is highly toxic to rats and mice.Some studies suggest its teratogenic and carcinogenic properties on rats and mice. It directly affects the central nervous system, causes liver and kidney (chronic glumerulonephrosis) damage6 in rats and mice. It also impairs the reproductory system of rats. Behavioural and neurological changes have also been noticed. Thyroid follicular damage in mouse has been reported. Endosulfan is known to damage the endocrine system, nervous system, circulatory, reproductory, respiratory and excretory systems and developing foetus.
The National Institute of Occupational Health (India) have linked the higher prevalence of neurobehavioral disorders, congenital malformations in female children and abnormalities related to male reproductive systems to the continuous exposure to endosulfan spray. The study was conducted among children in one of the villages in Kasaragod District (in the South Indian State of Kerala) where endosulfan was aerially sprayed. Endosulfan is implicated in the occurrence of adverse health effects particularly in rural communities in South East Asia, Southern Pacific and Sub-Saharan Africa.
In Sudan in1988, endosulfan barrels washed in irrigation canals caused fish kills and three people died after drinking water from the canal. In the Philippines, endosulfan accounted for the largest number of deaths due to pesticide poisoning reported in 1991. In Sulawesi, Indonesia, 32 cases of poisoning due to endosulfan have been reported from 1990 to 1993. In Columbia, 155 cases of poisoning (in 1994) and 60 cases (1993) of poisoning due to endosulfan were reported. In Northern India, 18 cases of endosulfan poisoning have been reported in 1995-97 by accidental over-exposure during spray. Endosulfan caused a rise in death numbers due to poisoning in Srilanka from 1994 to 1998.
The misuse of endosulfan to kill snails has resulted in the largest number of poisoning cases with fatalities in Philippines in 1996. Poisoning due to consumption of endosulfan-contaminated food is also reported from Turkey (2003).
Many cases of poisoningdeath in Guatemala, Costa Rica and other Central American countries have also been reported. In Feb 2002, two South African boys living near Ntabamhlophe, Kwa-Zulu Natal died following exposure to endosulfan. A police officer and 3 journalists were hospitalized after visiting the place several hours later. In 2000, a case of 44 individuals who consumed food accidentally contaminated by endosulfan was reported in rural India. One individual died in the incident. In 2004, 36 persons of all age groups in a rural area of Jabalpur, India were poisoned after consuming wheat-grains or flour contaminated with endosulfan.
The worst of all the cases so far reported are from three nations--- Cuba, Benin and India.
Can endosulfan cause cancer ?
Endosulfan is found to damage human red blood cells (RBC) at concentrations of 1ppb-1ppm10. Both alpha-endosulfan and beta- endosulfan are genotoxic to HepG2 cells8. Endosulfan is hepatotoxic, mutagenic, clastogenic and induce effects on cell cycle kinetics. Endosulfan [is known] has been shown to cause chromosomal aberrations in hamster and mouse and sex linked mutations in Drosophila. Endosulfan has caused mutations in bacterial and yeast cell. It is also known to cause mutations in mammals. A re-analysis data from a 1978 NCI (National Cancer Institute, US) study in Osborne-Mendel rats has revealed that endosulfan induced malignant neoplasms at all sites in male and female rats and endocrine organs in male rats.
Both sexes developed lymphosarcomas and female rats had neoplasms of the reproductive system21. Endosulfan is also carcinogenic for the liver of female mice. No accurate data related to the carcinogenicity of endosulfan in human is available but from field level reports, endosulfan can be highly suspected for having carcinogenic properties in human beings, especially in cases of chronic exposure. In some reports it is referred to as having possible carcinogenic effects, effects in human immune and reproductive system. Studies have also shown that it induces proliferation of human breast estrogen sensitive MCF7 cells in vitro9, which may lead to greater breast cancer risk. Studies also indicate the contribution of endosulfan in the combined effect of environmental estrogens in inducing breast cancer
The Conference of Parties to the Stockholm Convention in Geneva on Friday approved the recommendation for elimination of production and use of Endosulfan and its isomers worldwide, subject to certain exemptions.
The decision will not be binding on India unless specifically ratified by the country. However, the Indian delegation to the Convention concurred with the decision after its concerns about exemptions and financial assistance were addressed, according to information reaching here.