Some insects are pests and their control is desirable or necessary. Some methods of insect control create more environmental and health problems than others. This week in Geneva, Switzerland, The Stockholm Convention on Persistent Organic Pollutants is meeting. Topping the list of controversies is a proposed decision regarding the insecticide endosulfan.
Persistent Organic Pollutants (POPs) are organic chemicals that degrade in the environment at slow rates (persistent). These chemicals can volatilize and enter the atmosphere. The rate at which these chemicals are transported and deposited in other places is greater than the rate of degradation. POPs used in one location (or country) can become environmental contaminants in other countries. International treaties banning the use of the worst offenders is the only means that countries have of preventing contaminants from reaching their home soils. Numerous chemicals have been banned from use by international treaty. Banned chemicals include some familiar pesticides such as DDT and a number of the less familiar cyclodienes (a type of insecticide) such as aldrin, dieldrin, endrin and chlordane. The only remaining cyclodiene still in use, endosulfan, is under consideration for addition to the POP list.
Endosulfan was not included with the other cyclodienes initially because endosulfan is more readily metabolized and excreted by many organisms. It bioaccumulates (concentrates in tissues) to a lesser extent. However, newer information on endosulfan indicates that endosulfan and toxic metabolites do bioaccumulate in some organisms. Persistence data indicate that endosulfan and its toxic metabolite, endosulfan sulfate, can persist in the environment from 2 to 600 days depending on conditions. Endosulfan is transported globally and can be measured in arctic air in areas where no endosulfan is used.
The health effects due to low-level endosulfan contamination have not been clearly established. However, any chemical that accumulates in our tissues is cause for some concern. Alternative insecticides (to replace endosulfan) are available that do not persist as long in the environment.
The acute effects of endosulfan due to high level accidental exposure are well known. Endosulfan is one of the most toxic insecticides in use and its misuse has contributed to deaths and pesticide poisonings in many poor countries. Some groups in India wish to ban endosulfan as a means to protect poor farmers and rural residents from endosulfan poisoning. Poor farmers often are unable to read the directions for use, or may lack the appropriate equipment to use an insecticide safely.
Why is there a controversy? Northern European countries have already banned endosulfan use in Europe. They would like other countries to impose the same ban. Additionally, the manufacturers of the alternatives to endosulfan are located in Europe and could profit from a ban on endosulfan. The US has been slow to ban endosulfan from use. The US EPA continued the registration of endosulfan in 2002 but was sued by environmental groups to reconsider in 2007. Currently, registrations for use of endosulfan in the US are being phased out. This means that endosulfan will no longer be available or in use in the US in the near future.
The majority of endosulfan is used in India and China. Endosulfan is cheap- much cheaper than alternatives. Endosulfan has been off-patent for years so its price is subject to competition. The alternatives to endosulfan are all more expensive. They are under patent protection which restricts market competition and inflates their price. Poor farmers in many locations either use very cheap insecticides or none at all. They cannot afford to buy more expensive products. India is currently opposing the addition of endosulfan to the POP list for economic reasons.
Thus the protection of the environment from a persistent insecticide is embroiled in a controversy pitting wealthy corporations against poor farmers. Untangling the pieces to produce an outcome that is fair will require negotiation and compromise.