WASHINGTON — The North American Millers’ Association (NAMA) said it was disappointed with the Environmental Protection Agency’s (E.P.A.) proposal to revoke residue tolerances of sulfuryl fluoride on foods, which would eliminate “the only practical effective alternative to methyl bromide for controlling pests in mills.”

“The action E.P.A. proposes will strain already precarious food safety resources, with negligible benefits to public health,” NAMA said in response to the Jan. 19 E.P.A. proposal of a three-year phase out of the use of sulfuryl fluoride.

The phase-out of sulfuryl fluoride is critical to the grain milling industry because it was the primary replacement for fumigations to the pesticide methyl bromide, which currently is in the final stages of being phased out for broader environmental concerns as part of the United State’s ratification of the Montreal Protocol in 2009.

“The milling industry has complied by cutting its use of that compound (methyl bromide) by about 90% over the last six years,” NAMA said. “This difficult achievement was accomplished by cutting use wherever possible and filling in with sulfuryl fluoride only when absolutely necessary.”

Jim Bair, vice-president of NAMA, said, “Given the phase-out schedule of methyl bromide which is still in place, most mills had at least tried to utilize sulfuryl fluoride and some had switched over completely.”

But several changes to the sulfuryl fluoride label, which defines its legal use, and ongoing review created uncertainty and slowed mills’ testing and adoption of sulfuryl fluoride, he noted. Technical issues, such as increased sulfuryl fluoride gas needed in cold weather and to get complete pest control compared with methyl bromide, also impeded the switchover to sulfuryl fluoride, he said.

Because sulfuryl fluoride breaks down to fluoride after it is applied, the E.P.A.’s proposal to phase out the use of sulfuryl fluoride is part of its overall effort to reduce the amount of fluoride to which humans are exposed, according to the agency’s web site.

“Residues of fluoride due to fumigating commodities, mills and bakeries with sulfuryl fluoride constitute less than 3% of the total exposure to fluoride,” the E.P.A. said. “Since sulfuryl fluoride is an important alternative to methyl bromide, and because sulfuryl fluoride use is a very small contributor to overall exposure, E.P.A. has proposed a three-year phase out of use of sulfuryl fluoride.”

NAMA said acknowledgement by the E.P.A. that use of sulfuryl fluoride results in a “tiny” contribution to fluoride exposure, “elimination of sulfuryl fluoride will not significantly decrease the fluoride exposure problems identified by the agency.”

NAMA said a mill needs to be fumigated only once or twice a year. The process involves emptying grain and milled products from a facility to the extent possible, resulting in little if any wheat, corn or oats being directly treated with sulfuryl fluoride.

“We’ve known for some time this was a possibility,” Mr. Bair said. “The Fluoride Action Network, Environmental Working Group and Beyond Pesticides challenged tolerances for residues of sulfuryl fluoride on food back in 2005, shortly after E.P.A. registered it for structural and commodity fumigation uses. Those groups had vastly overestimated the amount of sulfuryl fluoride that was in use and possible residues on food.”

Remedial action against sulfuryl fluoride under the Safe Drinking Water Act was ultimately triggered by a 2006 report by the National Academy of Sciences urging the E.P.A. to conduct a new assessment of the risk of fluorosis, which concluded the risk an “adverse health effect” rather than a “cosmetic effect” as previously considered.

“The petitioners notified E.P.A. in the spring of 2010 that they were dissatisfied with inaction by the agency, were therefore withdrawing their petition and would be seeking a legal remedy,” Mr. Bair said. “Unfortunately, E.P.A. was not able to dissuade them of their concerns.”

According to the E.P.A., sulfuryl fluoride is a registered fumigant for insect pest control in closed structures and their contents. It was approved for additional direct treatment on additional harvested and processed food commodities such as coffee and cocoa beans, and for fumigation of food handling and processing facilities in July 2005.

In addition to use by grain millers, sulfuryl fluoride is used by the nut and dried fruit industries and for control of dry wood termites in homes, among other uses. NAMA said it was working closely with other industry groups such as the rice milling and pasta manufacturing associations, with sulfuryl fluoride’s manufacturer, Dow AgroSciences, and with technical experts in the milling industry.

The milling industry, as well as other industries that use sulfuryl fluoride, will have difficulty finding an adequate, effective and cost effective replacement.

“We expect the Integrated Pest Management techniques pioneered by the milling industry and still in place would be augmented by high heat, or possibly high heat in conjunction with low levels of phosphine or carbon dioxide,” Mr. Bair said. But he acknowledged there were significant “technical hurdles” to clear.

Phosphine is corrosive to electrical systems, computers and motors and mills don’t have heating capacity to bring temperatures up to the needed 135F to 140F and hold it for 12 hours or more to be effective, Mr. Bair said. Heat also may damage electrical systems, milling machinery and even mill structures, he added, and auxiliary heating equipment was very expensive.

Mr. Bair said NAMA’s technical committee will be reviewing the E.P.A.’s 109-page document on sulfuryl fluoride and will seek answers to identified questions. The public comment period ends April 19.

“NAMA will be aggressive in advocating the industry’s case to ease the transition should the agency act as it has proposed,” Mr. Bair said.