Eco-friendly fumigant

by Emily Wilson
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The first new type of phosphine application to be approved since the mid-1980s for use in U.S. flour mills and grain silos should be welcome news for an industry faced with phasing out methyl bromide use over the next four years.

Eco2Fume, a cylinderized phosphine and carbon dioxide-based fumigant, was granted full food registration last August by the U.S. Environmental Protection Agency. The environmentally friendly, non-flammable fumigant can be used in place of methyl bromide in flour mills, grain and food processing plants.

Phosphine and methyl bromide are the only major fumigants labeled for food use in the United States, and the use of methyl bromide is being phased out by the year 2005.

Eco2Fume was invented in the early 1980s by BOC Gases, an industrial gas company in Australia, and the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO). In 1999, Cytec Industries, Inc., West Paterson, New Jersey, U.S., purchased BOC's fumigant business.

The cylinderized mixture of 2% phosphine and 98% carbon dioxide is a highly effective fumigant in both sealed and unsealed facilities, according to Brian McSwigan, global business director for phosphine gases at Cytec, which is the registrant for Eco2Fume in the U.S.

The ready-to-use cylinders directly dispense the gas into structures from the outside, preventing any worker contact with the gas. Operators can easily control concentration levels.

McSwigan said Eco2Fume has tremendous possibilities for growth in the U.S. "We had our first Eco2Fume sale within days of receiving approval," he said. "Users are pleased with the results so far. The market has known about the product since 1996; people are relieved to actually see the product available."

The product is used on over 50% of the wheat stored in Australia and also is registered for use in South Africa, New Zealand, Cyprus and the U.S., while experimental trials are taking place in Denmark, China and Egypt. Cytec also has begun the registration process in the Caribbean island of Trinidad and Tobago, is finalizing registration preparations for Canada and is considering how to address the European market.

It has been predicted that the global target market for Eco2Fume is worth an estimated U.S.$40 million.

BETTER THAN METHYL BROMIDE? Although some experts say cylinderized phosphine is not a full replacement for methyl bromide, since it does not provide an "instant" kill, phosphine is generally considered to be a better penetrating fumigant than methyl bromide and diffuses more evenly over a structure.

As opposed to contact insecticides, which work only on the surface of grain, fumigants such as phosphine and methyl bromide are the only known pesticides that can penetrate a grain kernel or grain mass.

"Phosphine is a much slower-acting poison and it needs time to do its job properly," said Chris Newman, managing director of Grain Tech Systems Pty. Ltd., a fumigation company in Beijing. Newman has been working with Cytec to register cylinderized phosphine in China.

Newman said the reason phosphine is so important to the world's grain stocks is that there are so few alternatives. With the demise of methyl bromide, he said, phosphine will be the only fumigant that is both commercially available and effective for killing insects in grain.

"The search is on for new fumigants, but few people expect that any will be on the market in the foreseeable future," he added. "And if and when they are, it is unlikely that they will be as cheap and easy to use as phosphine."

CYLINDERS VS. PELLETS. Phosphine gas is released when aluminum or magnesium phosphide pellets react with moisture in the air. Cylinderized phosphine is produced with an acid process to combine phosphorus and steam to make a gaseous phosphine, which is liquified and filled into cylinders. The phosphine mixture is dispensed as a liquid from the cylinders, but immediately changes to a gas state when released into the atmosphere.

The largest producer of phosphine in the world, Cytec produces phosphine in Niagara Falls, Canada. The company also blends phosphine and carbon dioxide and fills cylinders at this location to supply North America. Cytec ships phosphine in cylinders to Australia to be blended into Eco2Fume for that market.

The only known competitor is one Chinese manufacturer believed to be producing cylinderized phosphine for domestic use, according to Newman.

Newman said cylinderized phosphine is "pure" phosphine gas — the same chemical that is generated by phosphide pellets but without the aluminum hydroxide and toxic phosphide residues left over from tablets.

"By its very nature, cylinderized phosphine can be turned on and off like water from a tap, and as a result the fumigant dosage can be very accurately controlled and maintained," Newman said. "This means that grain can be exposed to low concentrations of phosphine for prolonged periods of time, which gives the best results when it comes to killing insects."

Pellets generate phosphine in an uncontrolled manner, he said, within a few hours or days of being exposed to the grain. "In order to get a lethal dosage, it is necessary to release a lot of phosphine at the start of a fumigation in the hope that there might still be some gas left after a week," Newman said. "As a result, the total amount of phosphine released into the grain, and to the atmosphere, is much higher, resulting in higher residues in the grain and higher releases to the atmosphere.

David Mueller, president of Fumigation Service and Supply, Westfield, Indiana, U.S., which is providing training and technical support to Eco2Fume users in the U.S., said phosphide pellets usually follow a slow curve to reach a peak of phosphine release after about 10 to 20 hours, after which the phosphine concentration begins to fall. Cylinderized phosphine offers the ability to achieve the required concentration levels for a "kill" within one to two hours, he said, regardless of moisture level or ambient temperature.

Newman added that because of the uncontrolled nature of pellet fumigations, pockets of low concentration almost invariably exist in a silo fumigated with pellets, with the result that some insects are bound to survive.

"Like bacteria that is exposed to inadequate dosages of antibiotics, it has been discovered that insects gradually develop resistance to phosphine over time if they are allowed to survive," he added. "Therefore, widespread use of poor fumigation practices create the risk that phosphine will become ineffective as a fumigant in the future."

The importance of this has only been recognized by a few countries — Australia in particular, said Newman, who is an Australian. "Which is one reason why cylinderized phosphine has been so well accepted there," he added. "The other reasons are that it is much easier and much safer to use, since fumigators have only to turn on a tap to fumigate a grain mass without exposing themselves to the gas itself."

There also is no danger of spontaneous combustion, as there is with pellets, Newman said. He surmises that if an application for registration of pellets was made today, it would probably be rejected not just because of their toxic hazards, but from the risk of fire or dust explosion that exists when they are used in a silo.

ENSURING EFFICACY. In the U.S., Cytec is requiring that all potential users of Eco2Fume attend a free product stewardship training. The one-day session highlights product and safety information, case studies, dosage and exposure times, fumigation technique and includes an on-site demonstration.

"Product stewardship is the responsible and ethical management of the health, safety and environmental aspects of a product such as Eco2Fume," said Roger Cavasin, Cytec product manager, at a stewardship session in November.

Fumigation Service and Supply will provide technical support to Eco2Fume users. David Mueller and his brother, John Mueller, have been researching and testing Eco2Fume since 1996.

Cytec and Fumigation Service and Supply have already held four Eco2Fume stewardship meetings, attended by about 125 people. There are no specific plans for future stewardship dates. "We will wait for people to approach us now, and then we will either arrange a training session for interested parties, or we will meet and train people on an individual basis," David Mueller said.

"Everyone needs to go through this stewardship program — it is the right way to introduce a new fumigant."