Chemical warfare agents in pesticides used in Sri Lanka?

December 26, 2011, 8:42 pm , The Island.

By Dr.Channa Jayasumana
jayasumanalk@yahoo.com

The controversy regarding the presence of Arsenic (a heavy metal which is toxic to living beings) in pesticides available in Sri Lanka has now almost come to an end. It has been proved beyond any doubt that many pesticides available in the Sri Lankan market contain this toxic heavy metal. After debates, arguments, and investigations, almost all the relevant parties now have declared and accepted that Arsenic is present in insecticides, herbicides, and fungicides used in this country.

Representatives of multinational companies importing these pesticides, public officials and some academics now attempt to mislead the public by declaring that presence of arsenic in small quantities does not have adverse health impacts. However, contrary to such claims, the scientific and medical community has established that arsenic is a non-threshold Carcinogen, which in other words means that the presence of Arsenic even in microgram levels is harmful to the living beings.

In the case of Sri Lanka, Arsenic is present even in organic pesticides. It is rather unusual for a heavy metal like Arsenic to be present in an organic product even as an impurity. Therefore, its presence in these pesticides raises serious concerns regarding its original source.

A pesticide consists of two main components, namely, active ingredients and inert ingredients. The active ingredient is the specific compound designed either to kill or debilitate the pest. In general, the active ingredient forms a certain percentage of the pesticide mixture and the rest of the mixture comprises the inert ingredients that helps with their storage, handling and application and enhances their effectiveness or safety. In addition to these two main components, there may be some chemical compounds that are present as impurities.

Although inert compounds play a key role in increasing effectiveness of the pesticide formulations, such compounds are strictly regulated due to their adverse health consequences. In the US, the current list of approved inert ingredients of pesticides for agricultural use is listed in Electronic Code of Federal Registrations (e-CFR) of US Environment Protection Agency (EPA-USA 2011), and clearly states that Arsenic or Arsenic-related compounds should not be used as inert ingredients in pesticides. In addition, the International Union for Pure and Applied Chemistry’s (IUPAC’s) Technical Report on pesticide impurities published in 2003 has stated that arsenic cannot be present in any of the organic pesticides used in the world.

Arsenic-based pesticides are banned in Sri Lanka. The presence of Arsenic as an active ingredient in the pesticides sold to the farmers, therefore, is a direct violation of these regulations. Further, if arsenic is present in imported pesticides as an inert ingredient, these regulations require importers of pesticides to declare such presence to the Registrar of Pesticides. In addition, according to the same regulations, the impurities in pesticide formulations, too, should be reported to the Registrar of Pesticides, irrespective of whether they are present in the raw/starting material or formed during synthesis, storage or handling.

If arsenic is not an active ingredient, inert ingredient or an impurity, how has it come to be present in pesticides available in Sri Lanka? One important hypothesis which emerged after lengthy discussions with local and foreign experts is the possibility of intentional or unintentional contamination of pesticides by Chemical Warfare Agents (CWA). A CWA is a chemical substance, the toxic properties of which are used to kill, injure, or incapacitate humans. About 70 different chemicals have been used or stockpiled as CWAs during the 20th century by a number of countries, especially the West. During the time of World War II, USA, UK, Germany, China, and Japan have produced thousands of tons of CWA. These agents may be in liquid, gaseous or solid forms.

Admisite (10-chloro-9-10-dihydrophenarsazine), Clark-1 (Diphenyl arsine chloride), Clark-2 (Diphenyl arsine cyanide), and Lewisite (2-chloro-ethenyl dichloro arsine) are some of the most toxic chemical compounds ever produced by mankind and those have been used as CWAs. All these four contain arsenic as the key element. The additional presence of significant amounts of cyanide in almost all the arsenic-containing pesticides in Sri Lanka further strengthens the hypothesis of CWAs, especially Clark-2, contaminating these pesticides. If someone added few millilitres of CWA to a barrel of pesticides, toxicity of that pesticide would be enhanced remarkably and lethal dose (amount of chemical compound required to kill) would be reduced drastically. Nevertheless, the analysis of such a contaminated pesticide for arsenic will show only a small amount (ppb – parts per billion) of arsenic due to dilution.

Interestingly, after World War II, some countries did run experiments to use Arsenic-containing CWAs as insecticides and herbicides. The tested CWAs were very successful as pesticides but were not used in those countries as a result of increased awareness of their detrimental effects on humans and environment. However, the possibility of multinational companies based there, using CWAs to enhance the pesticides in this part of the world, cannot be ruled out.

Recently, the CWAs became the focus of a discussion by the global medical professionals due to an incident which in Kizaki area of Kamisu town, Japan. Hundreds of people in that area were taken to hospital with unusual symptoms related to central nervous system, and it was subsequently found that this condition was due to a leakage of arsenic-containing CWAs to the wells in the area, thus contaminating drinking-water. Scientists used a graphite furnace atomic absorption spectrophotometer to analyze the contaminated well-water and found small amounts of arsenic. Unlike in the case of Sri Lanka, these scientists did not disregard the significance of the presence of small amounts of arsenic in water but proceeded to further analyze its chemical structures. This far-sighted action of the Japanese scientists led the authorities to take remedial measures and save their people!

Therefore, it is imperative that the issue of arsenic-containing pesticides be addressed as a national priority. Scientists and relevant state authorities should focus their attention on proper identification of chemical structures in pesticides in Sri Lanka and plan and implement strategies to contain environmental pollution, particularly the contamination of ground water, soil and edible plants, with the arsenic in agrochemicals.