LA PAZ, BOLIVIA, NOV. 19 -- Tons of toxic chemicals dumped from thousands of tiny cocaine laboratories in the Bolivian tropics are creating ecological disaster zones affecting the entire Amazon basin, according to ecologists and a new environmental report.

"The irresponsible dumping of precursor chemicals is causing untold damage," said Gonzalo Torrico, undersecretary for social development, whose office is studying the problem. "The chemicals are being dumped into rivers and seeping into the soil in great quantities, and we are facing a disaster."

A report released this week by the League for the Defense of the Environment, the nation's most respected environmental group, estimated that up to 38,000 tons of toxic waste are dumped each year in the Chapare and Beni regions, where most of the labs used to turn the coca leaf into cocaine are located.

The report, using the official government figure of 136,413 acres of coca leaf produced for cocaine, calculated the quantities of 41 chemicals used to transform the leaf through three phases of production to obtain cocaine.

Bolivia is second in coca production to Peru, which cultivates an estimated 306,000 acres of it. Bolivia is the second-largest producer of refined cocaine, after Colombia, which processes much of the coca grown in Peru, according to police statistics.

Because large quantities of water are needed in each stage of the production, the labs are almost always built beside streams, and the expended chemicals are then dumped into these branches -- which become rivers of the Amazon system.

The problem has been further exacerbated by the fact that until a month ago, when police seized chemicals in raids, they too dumped the substances into the streams.

"In the past month, we have given orders to stop that," Torrico said. "We are trying to set an example."

Carlos Arze, a coauthor of the report, which was funded by the U.S. Agency for International Develpment, said hard data on the effects of the dumping were not available because it was impossible for technicians to visit the area, largely populated by small coca farmers who have at times been violent with outsiders.

There are an estimated 10,000 small labs in the Chapare region, most of which produce only two to three pounds of paste at a time.

"We know we have a big mess" but cannot be much more specific, Arze said. The report said the most damaging substance was the estimated 3 million gallons of kerosene that are discarded each year, because it does not break down chemically.

"Kerosene has the property of extending across the surface of the water, greatly diminishing the capacity to oxygenate," the report said. "This could induce massive asphyxiation of aquatic life. While it is only mildly toxic, it severely affects all flora and fauna encountered, especially plankton."

The report estimates that 309 metric tons of sulphuric acid and 7,000 metric tons of calcium sulphate also are discarded each year.

"Each of these, by themselves, modify soil and water acidity, severely affecting soil productivity and aquatic life," the report said. "Similar contaminating effects are to be expected from the rest of the chemical waste. The magnitude of the ecological damage being caused is multiplied even further when this water is being used for irrigation."

Most of the coca leaf, which grows on three-foot shrubs, is in the Chapare region, a once-lush zone between Cochabamba and Santa Cruz in the eastern region of the country, now being cleared by migrants seeking a better living through growing of the plant.

Torrico said the government was doing all it could to stop import of precursor chemicals through new controls and by working for international agreements. But he said much of the chemicals was smuggled in.

"Of all the chemicals necessary to produce cocaine, Bolivia only produces two: the coca leaf and small amounts of sulphuric acid," said Javier Dips, the national director of the recently formed Office for the Control and Registration of Controlled Substances and Precursors.

Most of the chemicals are said to come from Europe, especially Germany, and Brazil, which shares a long jungle border with Bolivia that is virtually impossible to patrol.

"In another five years, if the same pace is continued, the Chapare could look like a desert," said one international ecologist. "The ecosystem simply cannot absorb the quantities of poison being dumped into it."