"If we were following the treaty's rules, we wouldn't be producing any new material until the stockpile was drawn down. But for three years, the EPA has kept authorizing new production and adding to the stockpile," said David D. Doniger, a policy director of the Natural Resources Defense Council, a national environmental group.
But Drusilla Hufford, director of the EPA's stratospheric protection division, said an ample inventory was needed to provide a "cushion" to protect U.S. food growers from a "shock to the system" if production was interrupted.
The stock of methyl bromide, which has dropped 75% since 1991, continues to decline about 20% per year, which Hufford said allowed an "orderly reduction" as farmers and federal officials collaborated to find safer pest-killing alternatives.
"We need to have enough in the pipeline to ensure we don't have a sudden shortage," she said.
The EPA data also show for the first time that growers other than U.N.-designated "critical users" -- those whose market would be disrupted and that have no viable pest-killing alternatives -- are drawing from the U.S. stock.
U.S. tomato and strawberry growers and others deemed critical used 21 million pounds last year, but the total used exceeded 23 million pounds.
It is unknown which farms are using the 2.5 million pounds or what crops they grow. Because the stockpile was produced before the 2005 U.N. ban, EPA officials say, farmers can legally buy methyl bromide from chemical companies without seeking U.N. and EPA authority.
Chemtura Corp. of Middlebury, Conn., is the only U.S. methyl bromide producer. Its manager of fumigant product issues, David McAllister, said Wednesday that the stockpile was being "managed very responsibly" by the EPA and had dropped by nearly half in three years.
He said maintaining at least a year's reserve was critical for agriculture in case "there were a catastrophic interruption in supply or some sort of pest infestation that was unanticipated."
"Clearly if economically and technically viable alternatives were available, growers would be using them instead," McAllister said.
The EPA's Hufford said that unlike most countries, the U.S. agricultural sector was huge and diverse and faced a variety of pests, making its crops more vulnerable than those in the European Union and consequently more dependent on methyl bromide.
