The Food and Drug Administration responded Monday to a four-year-old petition from the Center for Food Safety and the Institute for Agriculture and Trade Policy, stating that the agency was in the process of formally withdrawing approval for the use of arsenic-based drugs in animal feed. The letter states that sponsors of three of the four FDA-approved arsenic-containing compounds added to chicken, turkey and hog feed have withdrawn their products from the market and have requested that the FDA withdraw their approval. The agency is doing just that, but has denied the withdrawal of drugs associated with the fourth compound, choosing to pursue scientific research and evaluation. Of the 101 drug approvals for arsenic-based animal drugs, 98 will be withdrawn. First approved as animal feed additives in the 1940s, arsenic-containing compounds have been fed to poultry to induce weight gain. A 2006 IATP report estimated that more than 70 percent of all U.S. chickens raised for food were fed arsenic and tests of the chicken in our grocery stores indicated that half of it contained detectable arsenic. CFS and IATP’s 2009 petition called on FDA to withdraw its approval of the compounds, arguing that they are not necessary in animal feed and could pose a public health risk. Organic arsenic compounds, they argued, are not only toxic, but can also convert to cancer-causing inorganic arsenic inside of chickens, in manure-treated soil, and in humans. FDA’s response comes after CFS filed a lawsuit compelling the agency to do so.