Monday, September 14, 2015

Endosulfan: Myths and Facts

I was reading the news on endosulfan victims needing better rehabilitation facilities in The Hindu last week when it dawned on me to write a post on it in a social platform for discussion. In our profession, we have the unique advantage to look at a social problem like this through the expert eyes of a biologist, biochemist and biotechnologist. So I went through many of the past expert analysis and reports for this article, which I believe could throw light on many facts and myths revolving around this issue.

The chemical:
Endosulfan is an organochloride broad spectrum contact insecticide and acaricide. It was initially registered as a pesticide in the USA in 1954 for use against a wide variety of pests affecting field crops. Based on the LD50 in rats, this chemical is Class II (Moderately Hazardous) in World Health Organization Acute Hazard Rankings. This is based on the acute toxic effects as well as developmental and reproductive effects on chronic exposure. The United States Environmental Protection Agency (US EPA) has categorized it as Category I (Highly Toxic) according to US EPA Acute Toxicity Rankings. It is not listed as a known carcinogen by IARC, US EPA or US NTP. But endocrine disruption caused by this chemical is validated in multiple pesticide toxicity lists in the US and Europe. The mechanism of action of this chemical is described to be disrupting the Na+ - K+ kinetics across biomembranes and disturbances in the Ca2+- ATPase and Phosphokinase activities in the Hayes and Laws Handbook of Toxicology (1991). In 1999, in the Casarett & Doull’s Toxicology: The Basic Science of Poisons, Klassen and Watkin explained an added mechanism by the cyclodiene part of this chemical. It partly inhibits GABA, blocking chloride uptake and results in partial repolarisation of neurons. This leads to a state of uncontrolled neuronal excitation. It was considered to be a contact poison without any systemic accumulation till Olea et al reported accumulation of this chemical in adipose tissues of children with dietary exposure. This led to the very important later findings of endocrine disruption leading to delayed reproductive development in exposed children.

In Kerala:
Though various reports on acute poisonings and isolated reports on chronic poisonings of endosulfan had been surfacing from time to time from around the world, it was in mid-late 1990s that increased incidence of certain health issues in Kasargod district of Kerala with a possible association to endosulfan exposure that got media and hence world attention. Kasargod has large areas of cashew plantations spread across many villages. Due to the hilly topography of this region, the plantations are interspersed between inhabited areas. Moreover, this also makes manual spraying of pesticides to these plantations practically difficult. Hence, the Plantation Corporation of Kerala (PCK) had arranged for aerial spraying of endosulfan in helicopters for more than 25 years against the tea mosquito pest affecting cashew plantations. This clearly violated the US EPA regulation of a 300ft spray drift buffer for endosulfan aerial applications. Dr. Mohana Kumar, a physician practicing in the area since 1982 published a report of his observation of increased incidence of certain health issues such as cancers, congenital anomalies, delayed puberty, mental retardation and psychiatric illnesses in the area in Down To Earth magazine in February 2001.

The health reports:
On 17th February 2001, about a month and a half after the last aerial spray of endosulfan in the region, Centre for Science and Environment (CSE) analyzed ground water samples from Padre Village of Kasargod using gas chromatography and reported the concentration of the chemical to be 7 to 51 times more than maximum residue limit (MRL). They also reported increased levels in isolated soil samples and serum of some individuals. As the study was not satisfactorily systematic, Frederick Institute of Plant Protection and Toxicology (FIPPAT) reanalyzed soil, leaf, water and biological samples from the area. They reported very low levels of the chemical in the collected samples contradictory to the previous report. With the controversies brewing intense, National Institute of Occupational Health (NIOH) of the Indian Council for Medical Research (ICMR) set an elaborate study on the chemical and physiological aspects of endosulfan in the population of Padre Village compared to neighboring Meenja Panchayat without any endosulfan exposure as control in 2002, about ten months after the last aerial spraying in the region. The study showed significantly high levels of endosulfan residues in the serum of 85% of female and 78% of male population studied. It was also reported that even though the incidence of health issues reported previously by Dr. Mohana Kumar was comparable to any subset of population, the serum levels of endosulfan in children with delayed puberty and congenital anomalies were significantly high. This corroborated with the previous evidence on endocrine disruption by the chemical. With an average field half life of fifty days, the expected levels in soil was very low. But long term exposure of over two decades had caused significant binding of the chemical to soil particles. Though the chemical is relatively insoluble in water, ground water sources showed significant levels of residue as the surface runoff collected over many years was high in endosulfan.

The legal battles:
There was a huge hue and cry over the health hazards of endosulfan in local and international media with Padre Village as reference. After nearly decade-long legal battles, The Stockholm Convention’s Persistent Organic Pollutants Review Committee (POPRC) in 2009 declared endosulfan as a Persistent Organic Pollutant (POP) setting the first step warranting global ban. In June 2010, US EPA finally terminated all uses of this insecticide to protect human and wildlife as its hazardous effects outweighed the limited benefits. Following this, the Pollution Control Board of the State Government of Kerala banned the use of endosulfan in November 2010. The production, distribution and use of endosulfan are completely prohibited by The Supreme Court of India from May 2011.

Two sides to the story:
The aerial spraying for over two decades was definitely unscrupulous and thoughtless when every pesticide control organization strictly advocates changing the chemical of use over two-three years to reduce risks to the ecology as well as resistance of pests. Moreover, with rivulets Panathur and Karicheri, the major source of drinking water to Kasargod district flowing through endosulfan exposed areas, the effect of chronic exposure to this chemical can affect the humans, cattle and fish of faraway areas too. Even after terminating the use, unused stocks of hundreds of gallons of endosulfan still remain in these areas awaiting detoxification and safe disposal. An accidental spill can pollute soil and water reserves to unfathomable scales.
The other side of this story was shared to RGCB Blog by one of the pediatricians in the medical team assigned by the state government to assess the health hazards in Kasargod. Many cases of cerebral palsy, hydrocephalus and growth restrictions have various antenatal and perinatal contributing factors. As the social and economic support for endosulfan victims is high, many unrelated cases may have been also included in the list just to avail the benefits. But, on the downside, this portrays a huge unrealistic health hazard picture to the outside world.

Though there is no absolute scientific proof of the actual genetic changes brought about by this chemical, an evidence of absence cannot be regarded as absence of evidence in this case. Re-registration appeal for this chemical is under consideration of US EPA. And government appeals for use of this pesticide in states other than Kerala and Karnataka are also under consideration in the Supreme Court. At this juncture, a systematic scientific analysis of the actual impact of endosulfan on human beings can, in fact, rescue the future generations from suffering.

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