Candles and Fragrances: That Cozy Atmosphere Has Some Caveats

The majority of candles sold in the US are made from paraffin wax, which is a byproduct of petroleum refining. When paraffin burns, it releases a range of combustion products including soot particles, carbon monoxide, and VOCs. A study published in the journal Chemosphere analyzed the emissions from paraffin candles and found they released benzene and toluene, both of which are toxic compounds also found in diesel exhaust. The concentrations in a well-ventilated room from occasional candle use are generally low. But regular use of multiple paraffin candles in a smaller, less-ventilated space can contribute meaningfully to indoor air pollutant levels.

Scented candles have additional concerns because of the fragrance. As covered in the personal care section, "fragrance" formulas are not required to disclose their individual chemical components. Fragrance compounds in candles volatilize when heated and become airborne. Some react with ozone in indoor air to form secondary pollutants including formaldehyde and ultrafine particles.

Wicks and Air Fresheners

Some candle wicks historically contained lead cores, which released lead into the air when burned. Lead-core wicks were banned in the US in 2003 but may still be present in older candles or candles manufactured overseas. Even without lead, synthetic fiber wicks can produce more soot than pure cotton wicks.

Plug-in air fresheners and synthetic room sprays are in some ways more concerning than candles because they operate continuously, maintaining a constant level of fragrance chemicals in the air. Many contain acetaldehyde and formaldehyde in addition to their fragrance components. Avoid these entirely if you want to meaningfully improve indoor air quality.

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