Perhaps no single Christmas custom is more ubiquitous than putting up the Christmas tree. …Today, that ancient tradition harvests 25 to 30 million natural Christmas trees annually. Artificial trees have drawn criticism for the chemicals used in their manufacturing. But live trees have drawbacks, too. One in particular — the agricultural chemicals and insecticides, fungicides and herbicides used in tree farming — has drawn remarkably little attention, partly owing to a lack of research on the risk to consumers or farmworkers. …Among the most common chemicals used by the industry are chlorothalonil, atrazine, glyphosate and dimethoate, all of which have known impacts on human health. …According to the Food and Drug Administration, Christmas trees are unlikely to impact the average home. In fact, assuming the tree is not ingested, the risk is considered so low that no testing is even done before trees are sold. Still, without testing, there’s really no way to be sure.