Candles make great decoration pieces and are a must-have for every self-care relaxing evening at home. Calming scents and flickering light is the perfect antidote to a hard day’s work. But what is the real impact of all this soothing mood-lighting? What is being released into the air, and can it affect our health?
Unfortunately, most mass-produced candles can have a negative effect on air quality. The wax and fragrance can release harmful compounds into the air, when lit or even when just sitting on your table. It all depends on the amount of petroleum-based ingredients in your candle.
Paraffin wax is derived from petroleum or coal - fossil fuels. It is mostly created as a by-product of processing and refining fuel. This wax would be extracted even if there were no commercial use for it. This means that it is abundant and can therefore be bought very cheaply. Paraffin has some favourable properties for use in candle-making - it burns slowly, and holds colours and fragrances well.
Two areas of concern when burning candles are toxins and soot. While there has been research linking burning paraffin wax to the release of benzene and toluene - known carcinogens - it must also be noted that the science has been muddied due to biassed funding of research. Some studies which found paraffin to release toxins may have been funded by interested parties in the soy industry, with the goal of sowing fear about paraffin in order to benefit the soy market, while other studies have found paraffin to not released any or very few toxins, but have been linked to the paraffin lobby or candle associations. Candle associations want to reduce fear surrounding candles in general. Unfortunately it is currently not possible to find an unbiased peer-reviewed study concerning toxins released while burning candles, regardless of which wax is used.
It is therefore more insightful to concentrate on the amount of soot and fine particles that each wax type releases when burning. Soot is made of the particles of carbon from the wax which was not completely burnt in the flame, combined with some steam. Out of all possible waxes used in candle making, paraffin releases the most amount of soot. While research into candles seems to be generally biassed, all research shows that paraffin candles release significantly more soot than other wax types (1)
Fine Particulate Matter
Soot is of particular concern because of its ability to reach deep into the lungs and build up, or even enter the bloodstream, causing health issues. Particles of soot, or particulate matter, which are 10 micrometres in diameter, also called PM10, can easily pass your nose and throat and enter your lungs. Even smaller particles, called fine particulate matter, which are 2.5 micrometres in diameter, PM2.5, can enter even deeper into your lungs. PM2.5 is of particular concern. Paraffin wax has been found to release 50 to 60 times more fine particulate matter, PM2.5, than soy candles. (2)
The European air quality target is 20 µg/m3 (3, 4) of PM2.5. The amount of PM2.5 released from paraffin wax after 45 minutes of burning was found to be 5.42 µg/m3. While this is around a quarter of the air quality target, it shows that burning multiple paraffin candles indoors can easily reach hazardous air quality levels. In comparison, a soy candle released 0.09 µg/m3 of PM2.5 under the same test conditions - a relatively insignificant amount. It is assumed that the amount of fine particulate matter released by other plant-based waxes such as rapeseed and stearin will be comparable to soy. In another study (5) it was found that beeswax releases around half the amount of fine particulate matter compared to paraffin.
The study (5) also found that the majority of fine particulate matter, PM2.5, was released when blowing out the paraffin and beeswax candles, which raised the level to around 30-40 µg/m3. It was found that using a snuffer to extinguish the candle kept the PM2.5 under 10 µg/m3 per candle. While it is assumed that plant-based waxes will release much less particulate matter when blown out, it is useful to know that using a snuffer can minimise the release of soot.
The aroma from a candle containing fragrance comes either from evaporation of oils from the cold wax when not burning, also called the ‘cold throw’, or it comes from the evaporation of oils from the melted wax pool below the flame, also called the ‘hot throw’. Concerning the production of soot, or fine particulate matter, fragrance can contribute to the creation of soot if too much was used in the candle. This excess fragrance in the wax can collect on the top of the melted wax pool and interfere with the wax reaching the flame, which can increase soot. Even if the correct amount of fragrance is used, there will inevitably be some fragrance which is burned, which also contributes to soot.
Another concern with fragrance is what compounds are being released into the air. There are two ways to give candles a smell - by using an essential oil, which is extracted from plants, or a fragrance oil, which can either be a natural or synthetic aroma. There is an open debate within the candle and fragrance community about which is more acceptable.
While essential oils are completely natural and plant-based, they are very volatile and evaporate from the cold candle wax over time, eventually leaving the candle without a scent. Essential oils can also be modified by heat, and change to an undesired scent when heated by the flame. Essential oils are highly purified plant components which can have an effect on the body, positively or even negatively. Essential oils can promote calm and relieve stress, and can help with ailments when used topically or ingested within safe amounts. However, essential oils can also produce unwanted physical reactions, such as skin rashes, inflammation, or an allergic reaction when inhaled. (6)
Fragrance oil is any aroma oil that is not an essential oil. Fragrance oils can be natural, such as a mixture of essential oils and plant-based carrier oils, or they can be lab-engineered aromas, often petroleum-based. Fragrance oil producers are not required to disclose the ingredients that they use. While safety data and precautions are provided with both fragrance oils and essential oils, it is often impossible to really know what is contained in a fragrance oil, because this is often not provided. It is therefore very hard for the public to make their own assessment of whether the fragrance oil fits to their values and intended safety level of their product - such as whether the oil is petroleum-free, natural or lab-engineered. If you are concerned about the effect that burning fragrance could have on your health, it would be safer to avoid fragranced candles, especially where the specific ingredients are not listed.
Here are some top tips to avoid possible health impacts from candles in your home:
- Use a plant wax such as rapeseed, soy, or stearin.
- Use a snuffer to extinguish the flame instead of blowing it out.
- Cut the wick to 0.5cm before lighting the candle.
- Avoid fragranced candles, especially where the exact fragrance ingredients are not listed.
made of unscented rapeseed wax