Recently, many jurisdictions have implemented bans or imposed taxes upon plastic grocery bags on environmental grounds. San Francisco County was the first major US jurisdiction to enact such a regulation, implementing a ban in 2007. There is evidence, however, that reusable grocery bags, a common substitute for plastic bags, contain potentially harmful bacteria. We examine emergency room admissions related to these bacteria in the wake of the San Francisco ban. We find that ER visits spiked when the ban went into effect. Relative to other counties, ER admissions increase by at least one fourth, and deaths exhibit a similar increase.