PITTSBURGH (AP) — In the Colorado mountains, a spike in air pollution has been linked to a boom in oil and gas drilling. A thousand miles away on the plains of north Texas, there's a drilling boom, too, but some air pollution levels have declined. Opponents of drilling point to Colorado and say it's dangerous. Companies point to Texas and say it's safe.The answer appears to be that drilling can be safe or it can be dangerous. Industry practices, enforcement, geography and even snow cover can minimize or magnify air pollution.The good news is that the technology exists to control methane gas leaks and other air pollution. The bad news is that the industry is booming so rapidly that some companies can't seem to get ahead of the problems.