To prepare for the "most wonderful time of the year," my family went to pick up our new Christmas tree that came equipped with built-in lights.

What we didn't expect when we unboxed it was this giant warning: "Cancer and reproductive harm."

We visited the link printed on the package and learned that the warning was for the holiday lights — which according to the site — can cause increased risk of cancer and reproductive harm.

It seems that some of the holiday lights we all buy at our local big-box store or pull out of storage every year are coated in harmful chemicals like lead.

If you look carefully on the packaging for products like furniture, vases and even certain foods, you're likely to see a Proposition 65 warning. That's thanks to the state of California, whose law "requires businesses to provide warnings to Californians about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm."

My family returned our tree and replaced it with one that doesn't have built-in lights. We're looking forward to decorating for the holidays and feeling safe while we do it.

Here's how you can make sure you're protected against any health risks as you shop for holiday decorations this year.

3 tips for decorating safely with holiday lights

Compared to other exposures during this time of the year, holiday lights are a mild concern, according to Dr. Fred Henretig, senior toxicologist at the Children's Hospital of Philadelphia.

During the holidays, poison control centers are far more concerned about young children getting into medications that belong to house guests, Henretig notes. 

Still, there are some things you can do if exposure to harmful chemicals from holiday lights concerns you. 

The Proposition 65 warning suggests:

• Washing your hands, and your children's hands, after setting up or removing holiday lights, especially if you're planning to prepare food or eat immediately after
• Ensuring that young children aren't playing with the lights or putting them in their mouths
• Aiming to use holiday lights that are labeled "lead-free"

"Some people [also] recommend that you wear gloves when hanging holiday lights," Henretig adds.

Why certain holiday lights pose risks of cancer, reproductive harm

When handling certain kinds of holiday lights, people can come in contact with chemicals like lead and phthalates – which is prevalent in many plastics, Henretig says.

"It seems to be predominantly in the wiring," he adds.

And the risk of cancer is likely associated with phthalates, based on studies that examine exposure to the chemicals and development of certain childhood cancers, he says. Though, there isn't much data in humans.

Still, phthalates have been linked to effects on hormonal balance and "may negatively impact childhood development cognitively," Henretig says.

As for lead exposure, the biggest concern is for pregnant women and children under the age of five or six, he says.

"I don't think this is a severe concern where people have to immediately throw out all of the lights in their home," he says. "I think that you should keep holiday lights out of the reach of young children."

Simply touching the lights isn't the issue, but touching your mouth after handling them before washing your hands can transfer the chemicals from the wiring into your body, according to Proposition 65's warning.

And for pregnant women, "these chemicals can pass from mother to baby," the warning states.

Low-level lead exposure can have adverse effects on children's cognitive abilities, says Henretig, including developmental delays. 

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