Why your scented candle could be harming your health

The atavistic flicker of the flame, the soothing smell; scented candles have gone from celebrity luxury to sitting-room stalwart; a firm favourite for creating an atmosphere of rest and relaxation in our homes.

They are also big business. Between March 2021 and 2022, UK consumers spent £418m on scented candles. Of our European counterparts, only Germany burns more than we do.

Far from baulking at the sometimes exorbitant price tag, we’ve become a nation who gifts them to each other, and buys them to treat ourselves. The cult of scented candle has led to sell-out concoctions such as Gwyneth Paltrow’s Goop “This Smells Like My Vagina” and Aldi’s £3.99 candles, prized by middle-class shoppers for smelling very similar to Tom Ford or Jo Malone versions – but for considerably less.

Apart from being a way to literally burn money, what’s the harm?

Well, many air quality experts are concerned that too few of us are aware of the potential dangers of our love of fragrant candles.

In fact, as we tackle external air pollution with restrictions such as ULEZ, few even think about the air quality in their own homes.

However, according to one Danish study, burning candles is the main indoor source of pollution particles.

“We like to make our homes as cosy as possible and candles give us a feeling of comfort, but I think there is a lack of understanding of what the actual effects are,” says Professor Christian Phrang, Professor of Atmospheric Science at the University of Birmingham.

What happens when we burn a candle?

The key pollutants produced as a result of burning a candle, according to Prof Phrang, are ultra-fine particulates such as PM2.5, which can enter the lungs. There will also be products of incomplete combustion such as carbon monoxide (CO), nitrogen oxides (NO) and sulphur dioxide (SO2), which are all harmful pollutants.

Breathing in unhealthy levels of PM2.5 can increase the risk of health problems such as heart disease, asthma, and low birth weight. Similarly, short-term exposure to SO2 can harm the respiratory system and make breathing difficult.

“People with pre-existing conditions such as asthma or COPD as well as vulnerable groups, such as children and the elderly, are particularly sensitive to these effects,” says Prof Phrang. He adds: “Sulphur oxides can also react with other compounds to form particles, which can penetrate deeply into our lungs and contribute to severe health problems.”

While the link between air pollution and physical health is now well documented, more recently, Professor Francis Pope, also a Professor of Atmospheric Science at the University of Birmingham, has been researching the effect of air pollution on cognitive health and mental health.

His team not only found that burning a non-scented candle resulted in concentrations of particulate matter well above the WHO guideline for PM2.5 but that it was linked to a temporary decline in global cognitive functioning after inhaling the polluted air for just one hour. In the 2019 study, groups carrying out tests were doing significantly worse if there’s candles in the room.

“There’s a growing body of work that suggests that there is a link between air pollution and cognitive health, both short term and also over the long term course of life.”

The field is relatively young at the moment, says Prof Pope. “But other academics have started to link air pollution to long term diseases like dementia and Alzheimer’s.”

The scent factor

On top of the pollutants being emitted from combustion, the inclusion of scent adds another layer of risk.

“Scented candles release aldehydes, such as formaldehyde in particular, and these are quite bad for health,” says Prof Phrang.

Aldehydes are irritants for the skin, throat, lungs and eyes, which can cause headaches, allergies and dizziness. They are also carcinogenic.

Combustion of the fragrance materials present in the candle may also include Volatile Organic Compounds (VOCs) such as benzene and polycyclic aromatic hydrocarbons (PAHs), which have all been linked to cancer.

Synthetic fragrances designed in a laboratory from a cocktail of chemicals should be avoided. But not even ‘natural’ smells made from essential oils are harm-free. “Essential oils consist of combinations of naturally-derived chemicals in concentrations much higher than those found in nature and some can trigger allergic reactions,” says Prof Phrang. “They can also lead to formation of formaldehyde.”

The act of burning a scent is worse than wearing it on your skin, says Prof Phrang: “The aldehydes are products from the burning process in the candle.”

Studies have shown that VOCs are emitted even when a scented candle isn’t burning.

The bad and the ugly

However, some scented candles are worse offenders than others.

“Some have a higher sulphur content and that means they might produce a hundred times more S02 than those with none. The wax or paraffin that they are made from makes a big difference.”

Rising concerns about air quality have propelled the demand for clean-burning candles made from natural materials.

A 2002 study published in the Journal of the American Oil Chemists’ Society found that soy wax, much like beeswax candles, burned at a significantly lower rate and resulted in less soot than paraffin candles

Prof Phrang recommends looking for natural material candles, adding: “Importantly, remember non-scented candles don’t release harmful aldehydes. A cotton wick is also best.”

How to burn them safely

Burning candles has been a quick way to create indoor air pollution for Prof Pope and his team. However if you want to limit particulates, his main tip is to make sure that your candle is burning cleanly.

“A candle that is burning nicely has very little particulate matter air pollution.”

Make sure the wick is always the correct length and the candle isn’t spluttering. “You can see when they’re sooty and creating smoke. And if you can see smoke, there’s air pollution.”

Other advice includes not burning them for prolonged periods of time as this leads to more VOC build up. Prof Phrang advises against ever burning them in the bedroom: “Particulates can stay in the room for many, many hours.”

If you do enjoy a scented candle then keep it as a distance from yourself: “You don’t want them under your nose,” he says.

How to reduce indoor air pollution

How polluted a room will become depends on how many you are burning, for how long and how well-ventilated the room is.

“If you burn one candle in a large room for a short time the pollution will be quite limited, but if you have many candles in a poorly ventilated area, it’s a different situation,” says Prof Phrang.

“Every candle has a certain emission profile and if you have twice as many you double it. It very quickly builds up.”

There are ways of mitigating indoor air pollution. The simplest way is to open the window.

“Unless you live next to a busy road,” says Prof Phrang.

Opening the window is something that’s not really in the DNA of the UK, he says: “In other countries it’s very common in the morning to just open the windows to lower the carbon dioxide in your bedroom.”

You can also use a filtration system such as a Hepa filter to remove particulate matter.

Should we switch to electric candles?

Putting the risk in context, by far the biggest emitter of indoor air pollution is open fireplaces, followed by wood burners.

“I would say wood burners are in nearly all circumstances significantly worse than burning a lot of candles,” says Prof Phrang.

While it would be extreme to ban the sale of scented candles, he thinks more people should be aware of the risks.

“If you’re healthy, having a single candle in your bathroom for two hours a week will not achieve a health impact.”

Still, as they are a non essential item, he recommends switching to electric candles that give the same flicker and cosy feeling.

Prof Pope, however takes a slightly less stringent approach: “If it is giving you joy or giving you pleasure, then that potentially outweighs the disadvantages.”

Overall, make sure you invest in high-quality candles and keep them in well-ventilated areas.

Source: Boudicca Fox-Leonard, Yahoo News UK