The telephone survey was conducted earlier this month, prior to the release of a much-discussed Associated Press investigative story reporting that drinking water in several major American cities contained trace elements of pharmaceutical drugs.
Americans' top three concerns, Gallup found, were the pollution of drinking water; the pollution of rivers, lakes, and streams; and the contamination of soil and water by toxic waste.
However, for all 10 of the environmental questions asked both this year and last, the percentage who said they worried a "great deal" about the problem is lower in 2008; in fact, concerns about drinking water actually declined by the largest amount.
Still, since the inception of the poll in 1989, polluted drinking water has topped the list of concerns every year the question has been asked - and even when it wasn't, a water-related worry finished first.
As for global warming, Gallup pollsters speculate that "the greenhouse effect" is a somewhat remote issue to Americans, whereas water quality is an immediate concern.