In recent years, the popularity of aromatherapy--the use of scent to induce certain moods or states of mind--has increased dramatically. Common ways to release fragrance into the environment include burning scented candles or incense or using potpourri in either a sachet or a ceramic pot with a candle beneath to heat it.
Like other fragrance products, candles, incense and potpourri can release many chemicals and are little regulated. (See Fragrances: What Your Nose Needs to Know for more on fragrance regulation issues.) When burned, candles emit small amounts of organic chemicals such as acetaldehyde, formaldehyde and naphthalene, according to one U.S. Environmental Protection Agency (EPA) report.
Candles Blow Smoke
Candles are also a source of indoor air pollution, according to the EPA, leaving black soot deposit (BSD) on floors and surfaces. Scented candles create the most soot.
BSD is primarily made up of elemental carbon, but may also contain phthalates and volatile organic compounds like benzene and toluene, which can cause cancer and neurological damage. BSD can be inhaled while airborne, but may also settle on surfaces like floors. BSD is especially attracted to electrically charged surfaces such as freezers, plastic blinds, TVs and computers.
Children may ingest BSD, after touching the floor or other surfaces and then putting their hands in their mouths. BSD, when inhaled, can lodge deep in the lungs, the lower respiratory tract or alveoli (very tiny tissue inside the lungs).
Lead can also be found in BSD, which is sometimes used in metal candlewicks, particularly those made in foreign countries. When burned, these wicks release lead dust in the air, which children can inhale or ingest, along with the soot. The dangers to children from lead poisoning are well known, including impaired learning and brain damage.
Though a voluntary industry ban on lead in candlewicks was instituted in 1974, many candles on the market today still contain lead. Public Citizen, a consumer group, petitioned the U.S. Consumer Product Safety Commission (CPSC) to ban and recall all candles with lead-containing wicks in 2000, and the agency is moving forward with the rule-making procedure on this issue. In the meantime, look for reassurances of lead-free wicks on labels before you buy a candle and avoid candles with stiff, metal wicks, opting for those that are made of cotton.
Incense is another source of indoor air pollution. When burned, incense sticks release particulate matter into the air. The tiny particles are easily inhaled into the lungs and can irritate airways. Several studies have linked exposure to incense smoke with cancer, asthma and contact dermatitis (skin irritation). One study reported that children whose parents burned incense during pregnancy or while nursing had a higher risk for leukemia. Carbon monoxide and benzene are also released when incense burns, as well as fragrance chemicals like musk compounds, for which there is little toxicity or health data, though they are persistent in the environment.
The burning of candles or incense also releases polycyclic aromatic hydrocarbons, or PAHs, are released, according to a study reported in the New Scientist. PAHs are common outdoor air pollutants (they also result from gas and diesel fuel burning) that may cause cancer and low birth weight. One Taiwanese study collected air samples from inside a temple where incense is burned regularly and compared them with samples taken outside and from a busy intersection nearby. The PAH levels from the temple were 19 times higher than the outdoor samples, and slightly higher than at the intersection.
Potpourri or Mothballs?
Potpourri is usually a mixture of dried leaves, flowers, spices and other organic materials bundled in a cloth sachet. It's also sold loose for use in baskets or small ceramic pots. While potpourri is often a safer option for scenting a room, some commercial sachets may contain paradichlorobenzene, a pesticide used in mothballs and a possible human carcinogen. Be sure to read labels!