Chronic toxicity of bromoxynil upsets transgenic cotton setup

The United States Environmental Protection Agency (EPA) will not allow growers to apply the herbicide bromoxynil to transgenic cotton during the 1998 growing season. What now for US farmers trapped in this 'genetics fix'?

In a letter to growers dated 24 December 1997 about the use of bromoxynil, EPA Assistant Administrator Lynn Goldman said the agency has "serious concerns about developmental risks to infants and children. In particular, we are concerned that the data show significant and irreversible human health effects."
    EPA had allowed time-limited tolerances for bromoxynil use on genetically-engineered cotton for more than two years; in a controversial 2 May 1997 decision, EPA extended the tolerance again.
    But time appears to have run out for growers of bromoxynil-resistant transgenic cotton. In her letter, Ms Goldman warned growers that applications of bromoxynil after 1 January 1998 "will likely result in illegal residues in cotton commodities, and would be subject to seizure if moved in interstate commerce."
    Rebecca Goldburg, head of the Environmental Defense Fund's Biotechnology Program, said the bromoxynil decision is the first time that EPA has "clearly stated that use of herbicide-tolerant crops to promote particularly hazardous herbicides is not acceptable."
    Jane Rissler of the Union of Concerned Scientists also welcomed EPA's decision. "Bromoxynil is a particularly bad herbicide," Ms Rissler said. "We'd like to see it off the market altogether."
    Bromoxynil is manufactured by Rhône-Poulenc. It is an integral component of Monsanto's 'Buctril BXN System' of transgenic cotton, which is genetically engineered for resistance to bromoxynil. In 1997, Buctril cotton was planted on 400,000 acres (160,000 ha) in the US, Rhône-Poulenc spokesman Rick Rountree said.
    Mr Rountree said Rhône-Poulenc was surprised by EPA's "sudden and abrupt reversal" which ignored safety assessments submitted by the company showing "even lower risks." Company officials met with EPA representatives on 23 January in Washington, and are hopeful that the decision might be reversed by 1 March in time for 1998 growing season.
    However, EPA's attorneys noted that such a decision might require a 90-day public comment period; a reversal by EPA would certainly cause an uproar in the environmental community.
    EPA is also re-evaluating all uses of bromoxynil and its metabolite DBHA as part of the re-registration process required by the Food Quality Protection Act (FQPA), a sweeping law passed in 1996 which requires the agency to review about 9,700 pesticide tolerances by 2006.
    Before FQPA was passed, EPA relied on a 10-fold uncertainty factor for both intra- and inter-species differences in its risk assessments, which added up to a 100-fold margin of safety; FQPA added another 10-fold uncertainty factor for risks to children and infants.
    EPA's Scientific Advisory Panel is scheduled to review the risk assessment for bromoxynil in March; the agency is expected to issue a Re-registration Eligibility Decision (RED) in April or May.
    FQPA established a "one-in-a-million" safety standard for cancer-causing pesticides. According to EPA's assessment, the risk from bromoxynil is 2.3 x 10 (-6) or 2.3 cases of cancer in a million. EPA is concerned that bromoxynil in cotton meal used for animal feed could work its way into the food chain and, in turn, humans.
    "EPA is retaining the extra 10-fold uncertainty factor mandated by the Food Quality Protection Act and cannot at this time make the safety finding required" to renew the tolerance for cotton, Goldman wrote.

Janet Byron, California, US, 16 February 1998.

[This article first appeared in Pesticides News No. 39, March 1998, page 16 ]