Small amounts of radioactivity from the Chernobyl nuclear accident turned up in precipitation Friday and Saturday in five U.S. cities, the Environmental Protection Agency said.

The radioactivity appeared in Salt Lake City; Jacksonville, Fla.; Santa Fe, N.M.; Albany, N.Y., and Cheyenne, Wyo., the EPA said. The maximum concentration in the five cities was 360 picocuries of iodine-131 in Santa Fe in rain Friday, the EPA said.

The highest readings were detected late last week in the Pacific Northwest. A rainwater sample in Portland, Ore., on Friday showed 5,250 picocuries of iodine-131 per liter. On Saturday, a Seattle rain sample had 2,400 picocuries. By Sunday, however, rainwater contamination had dropped to 90 picocuries in Portland and 1,400 in Seattle.

Air monitoring also reflected improvement at Northwest stations over the weekend.

A picocurie is a trillionth of a curie, a unit used to measure radioactivity.

The EPA has said that drinking a liter of rainwater contaminated with 500 picocuries of iodine-131 yields about the radiation dose of one-third of a chest X-ray.

In addition, the Food and Drug Administration has detected "very low traces" of radioactivity in a few shipments of food imported from Europe, but the traces present no health hazard, a U.S. government task force studying the April 26 Chernobyl accident said.