Levels of inorganic arsenic found in samples of chicken may be responsible for a slight increase in cancer risk to consumers over their lifetimes, according to a study by researchers at John Hopkins University published this week. That research comes on the heels of a lawsuit filed against the U.S. Food and Drug Administration two weeks ago by the Center for Food Safety and eight other government watchdog organizations which demands that the FDA respond to a three-year-old petition to disallow compounds containing arsenic from food animal feed. The samples of chicken in the John Hopkins study were collected in 2010 and 2011, just before Pfizer, the manufacturer of 3-Nitro (also known as roxarsone), an antibiotic containing arsenic, suspended sales of the product in summer 2011. Roxarsone had been given to feed animals to kill intestinal parasites and promote growth since the 1940s, though only recently did researchers find evidence that the harmless, organic arsenic in the drug could turn into carcinogenic, inorganic arsenic in meat. One other arsenic-containing drug, nitarsone, is still on the market. In 2011, the FDA’s Center for Veterinary Medicine concluded that the safe level of inorganic arsenic in chicken meat stood at 1 part per billion (ppb). The agency later revised that statement to say that any level of inorganic arsenic was concerning. The John Hopkins study analyzed samples of conventionally raised chickens that were fed antibiotics, antibiotic-free chickens, and organically raised chickens. Meat from those chickens raised with antibiotics had more than twice the amount of inorganic arsenic (1.8 ppb) compared with the antibiotic-free (0.7 ppb) and organic (0.6 ppb) chickens. Speaking to the New York Times, a spokeswoman for the National Chicken Council called those arsenic levels “very low” and noted that they reflected levels from before roxarsone was removed from the marketplace. Researchers found roxarsone in 20 out of the 40 samples of antibiotic-raised chickens, 1 out of 13 of the antibiotic free samples, and none of the 25 organic samples. Meat from chickens given roxarsone was found to contain arsenic at 2.3 ppb, while meat from roxarsone-free chickens contained arsenic, on average, at 0.8 ppb. That dosage of inorganic arsenic, the researchers determined, might result in an additional 3.7 cases of bladder and lung cancer for every 100,000 people eating chicken. Though Pfizer voluntarily suspended roxarsone sales, the FDA has not banned the product for use in feed animals. The company told the Times that it had no plans to reintroduce the drug. The coalition of watchdog groups led by the Center for Food Safety still wants FDA to place an outright ban on arsenic-based drugs. “FDA could easily and immediately fix the problem, but instead puts its head in the sand,” said Paige Tomaselli, senior staff attorney with the Center for Food Safety in a press release. “We can only conclude the FDA is catering to the companies that continue to sell products containing arsenic that ends up in our food supply.” In 2012, Maryland became the first state to ban arsenic-based drugs for feed animals. The John Hopkins study on inorganic arsenic levels in chicken meat can be accessed here.