(Beyond Pesticides, August 14, 2007) In an August 8, 2007 Federal Register Notice (72 FR 44510-44511), the Environmental Protection Agency (EPA) announced its decision to not initiate a Special Review for the commonly used herbicide 2,4-D, as well as the related herbicides 2,4-DB and 2,4-DP (dichlorprop). Despite evidence to the contrary, according to the FR notice, “Based on extensive scientific review of many epidemiology and animal studies, EPA find that the weight of the evidence does not support a conclusion that 2,4-D, 2,4-DB and 2,4-DP are likely human carcinogens.”
Although a mounting body of evidence links 2,4-D to various cancers, particularly non-Hodgkin’s lymphoma, EPA has been reluctant to classify it as a carcinogen in the face of industry pressure. EPA lists the herbicide in class D for carcinogenicity. Chemicals in this class are considered to have inadequate evidence for carcinogenicity, or not enough data is available. However, the link between 2,4-D and non-Hodgkin’s lymphoma has been demonstrated in the United States, Italy, Canada, Denmark, and Sweden.
A 1986 National Cancer Institute (NCI) study found that farmers in Kansas exposed to 2,4-D for 20 or more days per year had a six-fold higher risk of developing non-Hodgkin’s lymphoma than non-farmers. The risk of cancer was higher for farmers who mixed or applied the pesticide themselves. A 1990 study published in the journal Epidemiology (Vol. 1, No. 5) found a 50% increase in non-Hodgkin’s lymphoma in farmers who handle 2,4-D. Even a manufacturer’s study submitted to EPA in 1986 linked 2,4-D to rare brain tumors.
In 1991, an NCI study found that dogs were more likely to contract canine malignant lymphoma if their owners use 2,4-D on their lawns than if owners did not use the herbicide. When 2,4-D was applied four or more times per year, dogs were twice as likely to contract lymphoma. In addition to these epidemiological studies, a laboratory study conducted by the Food and Drug Administration (FDA) found a 4% incidence of lymphoma in rats exposed to 2,4-D and no lymphoma in unexposed rats.
EPA first proposed 2,4-D for Special Review in 1986. Two years later, EPA proposed not to initiate Special Review (53 FR 9590; FRL-3353-3), because it said the literature did not support a cancer link. EPA deferred a final decision until the completion of the 2,4-D reregistration eligibility decision (RED), which occurred in 2005.
EPA uses the Pesticide Special Review process when it has reason to believe that the use of a pesticide may result in unreasonable adverse effects on people or the environment. The Special Review process usually involves intensive review of only a few or just one potential risk. The review involves evaluating existing data, acquiring new information and/or studies, assessing the identified risk and determining appropriate risk reduction measures.
Known formerly as the Rebuttable Presumption Against Registration (RPAR) process, Special Review provides a mechanism for public input into EPA’s deliberations before the Agency issues a Notice of Final Determination describing its selected regulatory action. The Special Review process determines whether some or all registrations of a particular active ingredient or ingredients meet the federal standard for registration, or whether amendment or cancellation of portions or all of the registrations is appropriate.
TAKE ACTION: Let the Bush Administration know that politics should not trump sound science. Tell EPA what you think about its decision to not initiate a Special Review for 2,4-D, despite overwhelming evidence of its carcinogenicity. Contact EPA Administrator Stephen Johnson by email or call 202-564-4700.