The holiday season is approaching, when Americans will purchase one third of all candles sold this year. People like candles for the light, aroma, and ambiance they can lend a room. Some people even credit candles with air quality benefits. Beeswax candles are said to produce “negative ions [that] neutralize bad positive ions such as allergens, dust and air borne toxins thus improving air quality.”
But what is the truth about a candle’s impact on air quality in your home? First of all, the claimed benefits of negative ion production haven’t been independently verified. Research has been conducted on the potential health risk of air pollutants produced by candles burned in the home. In 2001, the Environmental Protection Agency’s Office of Research and Development produced a report on candles and incense and their effect on indoor air quality. These products can produce pollutants that may have negative health effects. In general, though, responsible candle purchase and use should not present an unreasonable hazard.
Safety and Health Concerns
All open flames are dangerous, and many house fires are started by candles each year. Between 2007-2011, candles were responsible for an estimated 10, 630 home structure fires in the United States, an average of 29 fires every day. Candle safety requires keeping combustible materials away from burning candles and never leaving burning candles unattended.
Candles also emit air pollution, and while this typically will not reach hazardous levels, it can in some situations. Purchasing the right candles and burning them properly can help you minimize the risk from using candles in your home. (Generally speaking, properly built and maintained fires should burn cleanly, with minimal smoke. The EPA’s Burn Wise program offers guidelines for proper burning.)
The most serious risk of air pollution in candles is from lead, which is sometimes used as a metal core in wicks. Metal wick candles may also contain zinc, tin, or other metals. Although lead use in candles was voluntarily ended in the United States in 1974, and then banned by the Consumer Product Safety Commission in 2003, it is still found in some candles. In a 2000 study by Public Citizen’s Health Research Group, 3% of candles tested contained lead, including candles from the U.S., Mexico, and China.
Burning lead-wick candles can lead to dangerous levels of lead pollution in your home. (Another major source of lead in the home is lead-based paint. In Harris County, the Healthy Homes Initiative seeks to uncover and remediate cases of lead poisoning in homes.) To avoid lead contamination from candles, buy from trustworthy vendors or avoid metal-wick candles in favor of cotton wicks. You can also check to see whether your candles contain lead (scroll to the bottom of this page from Green America Living for the “No-Lead Test”).
Candles emit toxic organic compounds, commonly including acetaldehyde, formaldehyde, acrolein, and naphthalene. Typical candle use will not produce hazardous levels of these pollutants. Only worst-case scenario tests (30 candles burning for 3 hours at a time in a single room) have resulted in organic pollutants exceeding the EPA’s 1 in 1 million excess cancer risk levels.
Some studies suggest that candles also emit polycyclic aromatic hydrocarbons (PAHs), which are found in diesel exhaust and can impact brain development in infants. Again, moderate candle use should not produce dangerous levels of these compounds.
Candles made from petroleum products, especially paraffin, emit more carcinogenic organic compounds than their natural counterparts. Beeswax and vegetable-based wax candles burn cleaner and release fewer toxins.
Candles are also a source of particulate matter, with most of the particles produced between 20 and 800 nanometers in diameter. This is several orders of magnitude larger than the PM10 (particles smaller than 10 micrometers in diameter, or “coarse particulate matter”) and PM2.5 (2.5 microns, “fine particulate matter”) regulated under the Clean Air Act. Still, large amounts of these particulates indoors can present a health hazard.
Scented candles are the major producer of particulate matter. Candles are scented with fragrant oils that are liquid at room temperature. These produce more soot than waxes, such as parrafin, that are solid at room temperature.
Black soot is produced by incomplete combustion of carbon-containing fuels such as candle wax. Black Soot Deposition is variously (and colorfully) known as “ghosting, carbon tracking, carbon tracing, and dirty house syndrome.” Candles are a major source of black soot deposition in households. To minimize soot production, make sure candles burn cleanly and keep them away from drafts.
Incense burning can emit air pollutants that may lead to asthma, cancer, mutagenic effects, and skin irritation. Air pollutants emitted from incense include the volatile organic compounds (VOCs) isoprene and benzene. Skin irritation may be caused by other compounds such as musk xylene, musk ketone, and musk ambrette. Carbon monoxide is emitted by incense burning, although in most circumstances it should not reach hazardous levels. Particulate matter and polycyclic aromatic hyrdocarbons (PAHs) are also emitted by incense. Generally speaking, if incense is regularly used indoors, it will be a source of air pollution in that room.
Alternatives to candles and incense are available. “Flameless” tealight candles with LED bulbs are a nice alternative for lighting. Aromatic benefits are available from essential oils, which can be used in diffusers or room sprays.
In general, though, burning one or a few attended candles in a room should not present health hazards from air pollution. As with any potential hazard, responsible and moderate use is key.