Tawatchai Hongtrakul, Pinya Chulintorn,
Wipa Thangnipon
and Sivaporn Sakulthiengtrong
Ministry of Agriculture, Thailand
Of twelve chemicals on the initial
list of the POPs Convention, nine are pesticides, including aldrin,
chlordane, DDT, dieldrin, endrin,
heptachlor, mirex, toxaphene,
and hexachlorobenzene (HCB). All POPs pesticides used historically in
Thailand were imported. These
pesticides were applied to crops, ornamental plants and lawns, and buildings.
Agricultural uses include field applications on cotton, corn, soybean,
rice, pineapple, sugarcane, citrus, and vegetables.
For structure pest control, these chemicals were applied to soils to
kill termites. DDT was used
heavily both in agricultural production and for malaria control. Two compounds, Mirex
and HCB, were never imported and used as pesticides in this country.
Because of their persistent nature and widespread used, analysis of pesticide residues in agricultural commodities has found POPs pesticides to consistently contaminate test samples. Awareness of the problems associated with pesticides has been gradually increasing. The first regulatory measure, the Poisonous Act B.E. 2510 (A.D. 1967), was issued more than 30 years ago. To date, the Hazardous Substances Act. B.E. 2535 (A.D. 1992) has been used to regulate the importation, distribution, registration and use of pesticides. Endrin was the first POP pesticide to be banned in 1981. Presently, all POPS pesticides, and some highly toxic organophosphorus and carbamate pesticides are banned. However, the widespread use of these pesticides for a long period of time inevitably resulted in the distribution of chemicals into the environment. Findings from nationwide pesticide monitoring programs conducted by the Pesticide Research Division, Department of Agriculture, during the past decade, have shown that the main rivers of Thailand have been contaminated with pesticide residues. POPs pesticides were the major contaminants detected. More than 50 % of water and sediment samples collected from the major rivers in agricultural areas were contaminated with DDT & derivatives, endosulfan & derivatives, dieldrin, aldrin, heptachlor & epoxide, dicofol, BHC, endrin, and chlordane. Residue levels in water and sediments ranged from 0.01 – 1.20 ug/L, and from 0.01 - 7.43 mg/kg, respectively. However, none of the residues detected in water exceeded the maximum allowable concentration (MAC) for drinking water.