They suggested money raised by the tax be put into a new fund to be spent on a scheme to gradually convert the country's conventional farming to organic agriculture, heal the chemical-induced damage done to the environment and ensure food safety.

They are drafting a bill similar to the legislation that constituted the Thai Health Promotion Foundation, which was established to promote public health using excise taxes on "sin products" such as alcoholic beverages and cigarettes.

The highest tax rate of 30 per cent is suggested for the most toxic group of agricultural chemicals including pesticides and insecticides, whereas other les toxic chemicals such as fertilisers should be subjected to lower tax rates.

Unlike the industrial sector, the use of chemicals in the agriculture sector lacks proper control resulting in excessive use that leaves toxic residue in the environment, especially in the ground water, said Assoc Professor Teerana Bhongmakapat of Chulalongkorn University's Faculty of Economics.

The effect of chemical abuse was also shown in the health of farmers, he said, adding the prevalence of toxic poisoning had doubled in less than a decade.

"If you count the cost of damage as a result of chemical use in agriculture we've lost more than the slim profits gained from exports of agricultural products," he said.

The total product-export profit generated was less than 30 per cent of the total value of agricultural chemical imports, not to mention the losses in natural resources and public health, which cost at least 30 per cent of the same import value, Teerana said.

The average tax rate for all types of agricultural chemicals would be about 10 per cent, said Asst Prof Sathitpong Thanaviriyakul also from Chulalongkorn's Faculty of Economics.

Altogether, the total tax revenues to be collected from the maker and distributor of chemicals should be about Bt5 billion per year and this amount of money should be spent to reverse the consequences of chemical abuse, he said.

The organisation to manage the fund should be a new independent body and the money should be used through the budgetary system, Sathitpong said.

Farmers would be forced to use minimal amounts of chemicals because of the higher cost. To reduce the adverse effects of taxation, the fund will subsidise the affected farmers and help them to change from conventional to organic agriculture.

Organic products had become increasingly popular in the world market, said Teerana, adding the market for these products in the United States, Canada, Europe and Japan had grown about 15 to 30 per cent per year.

Yet when compared to the potential export competitors in Indo-China like Cambodia, Vietnam and Laos, Thailand was at a disadvantage because the country had caused more damage to its agricultural structure, such as soil and water, from years of excessive chemical use.

"It's time to do something," he said.

Arthit Khwankhom

The Nation