Close your eyes, and with a simple breath, relax and travel. Thanks to the sole power of a scented candle, with a sweet and spicy, gourmet or floral scent. Let yourself be soothed by the little dance of its flame and its delicate fragrance.
At the local supermarket or in luxury boutiques, there are scented candles for all tastes, all flavors, and for all budgets. A perfect little cocooning gift to offer or treat yourself to during the winter and as the end of the year festivities approach. But is it safe for health? Do their scent and their combustion make them an ally of indoor air or an additional factor of pollution? What if they were to be lit in moderation?
A source of ultrafine particle emissions
When you don’t know too much about it, a scented candle is wax, a wick and a fragrance. In short, nothing too bad. Lighting one would be a harmless, even purifying gesture. This is what 68% of consumers think, who believe that scented candles have no effect on indoor air quality. And nearly a quarter of these users of scented candles (23%) light them in the belief that it improves the quality of the air in their interior, according to a TNS Sofres survey quoted by Ademethe ecological transition agency.
We are quickly undeceived by putting our nose in the studies carried out on the subject. “As they burn, scented candles emit ultrafine particles,” says 20 minutes Isabella Annesi-Maesano, research director at Inserm and epidemiologist of allergic and respiratory diseases. “Fine particles, generated in particular by road traffic with the combustion of hydrocarbons, or by domestic heating, measure 2.5 microns [soit 2,5 millièmes de millimètres], and are harmful to respiratory health. The ultrafine, they measure 0.1 micron, even a few nanometers, explains the epidemiologist. And according to the data we have, we know that the finer the particles, the more they penetrate to the bottom of the bronchial tree to reach the pulmonary alveoli, which allow oxygen to go into the blood. There, because of their size, they manage to cross the alveolar barrier, a kind of net with very tight meshes, and to pass into the blood. This makes them very harmful to cardiovascular health”.
Is there any sign that a candle is emitting ultrafine particles? “It’s when it generates black smoke during its combustion,” replies Isabella Annesi-Maesano. If there is soot on the wax or the glass wall of the candle, it is not good”.
A source of volatile organic compound emissions
And that’s not all. “These candles also release pollutants, emitted by their fragrance, whether synthetic, natural or based on essential oils,” adds the epidemiologist. Products which, on combustion, are the source of volatile organic compounds (VOCs) which are dangerous to health. “The main volatile pollutants emitted by candles are toluene, formaldehyde and acetaldehyde”, as well as “low emissions of benzene”, confirms Ademe in a report on “exposure to pollutants emitted by candles and incense in indoor environments”.
Admittedly, “the levels of volatile pollutants emitted are significantly lower than those recorded for incense”, tempers Ademe, but “formaldehyde, acetaldehyde and toluene are measured at concentration levels of several micrograms per cubic meter “. And the pollution doesn’t stop when you blow out your candle. The agency observes “a slight decrease in formaldehyde concentrations after the end of combustion, or even an increase in post-combustion concentrations for several candles tested, which probably indicates secondary emissions of these products”.
Clearly, “scented candles emit some of the most dangerous VOCs for health, in particular formaldehyde and benzene, classified as proven carcinogens for humans by the International Agency for Research on Cancer (IARC)”, insists Isabella Annesi-Maesano. VOCs which can also have “toxic effects on reproduction. But in the first place, all these pollutants emitted can cause respiratory diseases such as asthma, eye conditions, skin conditions and cardiovascular disorders,” she adds.
Tips for improving indoor air quality
Of course, the worst evils do not occur simply by lighting a scented candle for a few minutes from time to time. What is problematic, “is the very high level of indoor pollution: in the measurement work carried out by the Indoor Air Quality Observatory, we found a lot of formaldehyde in many homes, explains the epidemiologist. There is this widespread but erroneous belief that outdoor air is more polluted, but indoor air is more polluted: there are a huge number of pollutants in homes, more than 5,000 minimum, especially since there are It’s not just in the air, but also in the ground, in water, in a lot of new furniture or in cleaning products. And scented candles. However, we do not have complete data on the cocktail effect of all these pollutants”.
Hence the importance of reducing indoor pollution generated by candles. First gesture valid both against the pollutants of the candles and against the viruses which are currently rampant – Covid-19 and flu in mind –, “you must ventilate your accommodation, every day, and several minutes when you extinguish your candle”, prescribes Isabella Annesi-Maesano. And before that, it is better to choose well what to light it with. “The use of matches represents an additional source of particles at the very beginning of combustion, warns Ademe. The use of a lighter makes it possible to limit these particulate emissions”.
And for the air to be as free of pollutants as possible, it is recommended not to light several candles, not to place them too close to each other, nor near a window or an air vent, to avoid that the flame does not stir and generate smoke, therefore ultrafine particles.