With bacteria-shaped pom-poms attached to their hats and shirts, activists marched outside a pharmaceutical convention Wednesday in Philadelphia, warning that industry dumping of antibiotic residues could cause microbes to become resistant to the life-saving drugs.

"Hey, hey! Ho, ho! Pharma pollution has got to go," cried the 14 representatives of Mighty, an environmental advocacy group.

Some pharma firms based in India have improperly disposed leftover antibiotics and related chemicals used to make them, leading to the growth of drug-resistant microbes in the groundwater, they said.

People can then be exposed to the bacteria via drinking and swimming, said Casey Farrington, one of the marchers from the Washington, D.C.-based group.

Among the onlookers was Basava Bhaaskara, the chief executive officer of Roerich Healthcare, a pharma firm in Hyderabad, India.

Bhaaskara, who was attending the CPhI North America conference at the Convention Center, said his firm was not among the offenders, but he agreed that improper dumping was an issue.

"It is a problem for antibiotics to get into nature," he said. "After some time, the antibiotic doesn't work."