PITTSBURGH (AP) — Public health advocates and doctors on the front lines of Pennsylvania's natural gas-drilling boom are attacking the state's new Marcellus Shale law, likening one of its provisions to a gag order and complaining that vital research money into health effects was stripped at the last minute.Doctors say they don't know what to tell patients who suspect their ailments are related to nearby gas industry activity because of a lack of research on whether the drilling of thousands of new wells — many near houses and drinking-water supplies — has made some people sick.Health professionals around the country also say more research is needed.The industry says gas drilling is safe, and has provided a huge economic boom to consumers and workers..