The point of factory farming is cheap meat, made possible by confining large numbers of animals in small spaces. Perhaps the greatest hidden cost is its potential effect on human health.

Small doses of antibiotics — too small to kill bacteria — are fed to factory farm animals as part of their regular diet to promote growth and offset the risks of overcrowding. What factory farms are really raising is antibiotic-resistant bacteria, which means that several classes of antibiotics no longer work the way they should in humans. We pay for cheap meat by sacrificing some of the most important drugs ever developed.

Last week, the Natural Resources Defense Council, joined by other advocacy groups, sued the Food and Drug Administration to compel it to end the nontherapeutic use of penicillin and tetracycline in farm animals. Veterinarians would still be able to treat sick animals with these drugs but could not routinely add the drugs to their diets.

For years, the F.D.A. has had the scientific studies and the authority to ban these drugs. But it has always bowed to pressure from the pharmaceutical and farm lobbies, despite the well-founded objections of groups like the American Medical Association and the World Health Organization, which support an antibiotic ban.