After tests showed a rise in the number of homes with elevated levels of lead, New York City health and environmental officials are advising residents to run their tap water for at least 30 seconds before using water to drink or cook. But officials say there’s no cause for widespread panic, merely caution. The tests, which were done in older homes known to have lead plumbing, showed 14 percent of samples exceeding allowable levels. Last year it was only 5.4 percent, and the EPA requires public notification above 10 percent. The last time the city issued a public advisory was in 2005. Since hot water absorbs lead more easily, authorities advise running it until it’s cold. Besides, you wouldn’t want to accidentally cook those tiny invisible shrimp.