I've read this too. The study was done on pre-cut trees. We cut our own real trees, from tree farms. We've never had a problem with mold! We have noticed a very musty smell, when we bought a tree from home depot, or a grocery store. They are wrapped in plastic wrapping when delieverd and hold all the moisture in. A tree in the open air, should not have that problem. Lead, is actually the least of my worries in artificial trees. The chemicals in those, are horrendous. My husband wanted a fake tree one year and we just about gagged, at the chemical smells. We get our live tree about 2 weeks before Christmas and keep very little water in the stand. My husband has very sensitive sinuses and respiratory issues and we've never noticed a problem with the tree, from the farm. The pre-cut trees really gave him a hard time.