People buy fake Christmas trees for all sorts of reasons: allergies to tree pollen, an easier cleanup, a firefighter in the family who’s scared you away from the real ones.

But are you just as safe with an artificial fir as you are with a real-life tree? You have to be, right? After all, in 2014 alone we spent $1.19 billon on the damn things.

Unfortunately, that’s a complicated question.

To understand the answer, you first have to know what these trees are made of, and usually, that’s a synthetic plastic called polyvinyl chloride (PVC)—which is also used in construction pipes, toys, medical devices, and car interiors.

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The American Christmas Tree Association—a non-profit that educates people about Christmas trees both real and fake—says that PVC is “not harmful” or “dangerous.” But many experts disagree. 

That’s in part because PVC is a fire-resistant compound that can use metals like lead, tin, or barium as stabilizers, said Dr. Glenn Harnett, chief medical officer of American Family Care, the nation’s leading urgent care provider. As a result, a study from 2004 even found traceable amounts of lead in artificial trees.

“PVC also releases gases known as volatile organic compounds, which are gases that can irritate the eyes, nose, and lungs,” Harnett said.

In some cases, PVC may also contain phthalates—recognized endocrine disrupting chemicals shown to lower testosterone in lab animals and humans, said Dr. Bruce Lanphear, a professor of health sciences at Simon Fraser University.

The bigger issue: It’s hard to tell what’s really in your tree.

Why? As Lanphear puts it: “Over three quarters of chemicals found in consumer products have not been sufficiently tested for reproductive toxicity or for the ability to cause behavioral or cognitive issues, so they’re assumed to be safe.”

Because we do a relatively poor job of regulating the chemicals, he adds, some slip through the cracks as unintended contaminants. This is why—every now and then—we see reports about excessive levels of lead in products like makeup or toys.

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But do you really need to worry about the possibility of small amounts of chemicals lurking around? 

Lanphear said it’s tough to quantify the result of being exposed to your fake tree six hours a day, one month a year, for 10 years. But he says we’re all exposed to a variety of products all the time that can contain things like lead and phthalates, and that even at environmentally acceptable levels, this can potentially cause toxic effects on fertility and diminished testosterone levels in blood. 

“Lead exposure is an established risk factor for hypertension, infertility, and in kids, a diminished IQ,” he added. And in fact, the Centers for Disease Control and Prevention (CDC) says there is no safe level of lead exposure.

But there are some ways to protect yourself. Products made from PVC tend to release more harmful gases when first exposed to air and as they start to degrade, said Harnett.

So take the tree out of the box and put it outdoors when you first buy it.

“The longer you’re able to let the tree air outside of your home, the better,” he says. “And then don’t hold onto it forever. PVC plastic begins to weaken after nine years, Harnett said. So replace your tree before then, as you could be more exposed to metals when this happens.

Also: Look for a PVC-free trees made from polyethylene— a stronger plastic generally considered safer and not known to leach harmful chemicals, Harnett said. Companies like Balsam Hill have begun using polyethylene. 

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And no matter your tree, double-check your lights. 

One report from Cornell found detectable levels of lead in Christmas tree light cords that exceed the limits set by the U.S. Environmental Protection Agency and the Department of Housing and Urban Development. 

They recommend that children don’t handle lights, and that anyone who does should wash their hands immediately afterward.

This article orginally appeared on MensHealth.com.