Maybe you like a little festive pine scent in winter. Or a calming vanilla smell helps you relax after a hectic day. Perhaps it's just what you use when a kitchen mishap or the wet-dog stink needs disguising.

But you may want to think twice before lighting your next candle.

Some scented candles could be as harmful — maybe even worse — than smoking a cigarette.

That's according to Andrew Sledd, M.D., a Missouri pediatrician who specializes in environmental toxicology. Sledd told KFVS-TV that it only takes an hour of burning a candle to produce the same harmful effects as smoking just one cigarette.

He said soot from candles can pose a threat to our respiratory systems. That soot can contain particles of zinc, tin and lead. Because candles don't have filters, which typically remove microparticles, he said those soot particles are released into the room and can penetrate your lungs.

According to the EPA, the amount of soot produced can vary greatly from candle to candle.

A study on candle emissions by environmental and health researchers from the University of South Florida found that candle soot may include phthalates, lead, toulene and benzene. Scented candles, according to the EPA, are the major source of candle soot. Other factors that can increase the amount of soot include longer wicks and burning a candle in a draft, according to an EPA report on candles and indoor pollution.

A 1997 study from researchers at the University of Bayreuth in Germany found that burning candles emit trace amounts of organic chemicals, including acetaldehyde, formaldehyde, acrolein and naphthalene.

Getting the lead out

candle wick in melted waxSome candle wicks used to have lead wires to keep them from drooping and falling into the melted wax. (Photo: Brendan DeBrincat/flickr)

Metal wire is sometimes put in candle wick cores to keep them from drooping into the melting wax.

According to the EPA, lead was often used in the wicks. There was concern that the lead in the candle wicks led to increased emissions in the air. The National Candle Association voluntarily agreed to stop using lead wicks in 1974 and they have been banned in the U.S. since 2003.

There's still a chance imported candles might have lead wicks. To be 100 percent sure, look for the "lead-free" label.

The difference in candle types

A candle chemical study by researchers at South Carolina State University found that petroleum-based paraffin candles "released unwanted chemicals into the air," said lead researcher chemistry professor Ruhullah Massoudi.

"For a person who lights a candle every day for years or just uses them frequently, inhalation of these dangerous pollutants drifting in the air could contribute to the development of health risks like cancer, common allergies and even asthma,” said Massoudi.

None of the vegetable-based candles tested for the study produced any toxic chemicals.

The National Candle Association refutes the study's claims, telling The Huffington Post: "The safety of scented candles is backed by decades of research, fragrance testing and a history of safe use. The fragrances approved for candle usage — whether synthesized or 'natural' — do not release toxic chemicals. Health and safety studies are conducted for fragrance materials used in candles, including toxicological and dermatological tests."

Choosing safer candles

beeswax candlesBeeswax candles are typically safer and have the extra advantage of supporting the beekeeping community. (Photo: maxstockphoto/Shutterstock)

If you like the look of a flickering flame but worry about possible safety concerns, you have options.

Choose candles made from soy wax or beeswax. Their smoke poses less of a health threat than paraffin candles.

Some people prefer beeswax because they support the beekeeping business, burn longer than traditional candles, and give a faint honey-like scent.

Soy candles are also long-burning and as MNN's Matt Hickman points out, companies that make soy candles (and typically beeswax) typically use recycled packaging and lead-free wicks.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.