Expert issues candle warning after shocking experiment revealed cancer-causing emissions: ‘They’re one of the biggest sources of indoor air pollution’

Lighting a candle at can create a cosy ambience – but it could also be quietly harming your health.

New research suggests that smoke from candles burning indoors, especially in poorly ventilated rooms, can release a cocktail of chemicals linked to cancer.

And with around 64 per cent of UK households regularly lighting scented candles, experts are raising fresh concerns that the synthetic fragrances used to create them may be polluting the air inside our homes.

Some experts have also raised concerns about paraffin wax, the most common material used in mass-produced candles. 

Paraffin is a by-product of petroleum refining, making it inexpensive and effective at holding fragrance and colour. 

Some manufacturers market paraffin under the name ‘mineral wax,’ though it refers to the same petroleum-derived material.

When paraffin candles burn, they can release small amounts of volatile organic compounds (VOCs) such as benzene, toluene and formaldehyde. 

These chemicals are also produced by other forms of combustion and, at high levels, are known to irritate the respiratory system and are classified as carcinogenic.

Another potential source of emissions is the synthetic fragrance added to many scented candles. 

Some fragrance mixtures can release phthalates, chemicals used to help scents last longer, which have been linked in some studies to disruption of hormone systems.

Burning candles also produces hydrocarbons such as alkanes and alkenes, compounds that are created whenever organic material burns. 

These chemicals are also found in sources like vehicle exhaust fumes and other internal combustion processes.

Paraffin candles can generate more soot than many plant-based waxes, particularly if the wick is too long or the candle burns unevenly. 

The effects are generally greatest in poorly ventilated spaces, where combustion by-products can build up in indoor air rather than dispersing. Opening windows or limiting burn time can help reduce exposure.

Writing in The Conversation, a researcher from Aarhus University in Denmark described experiments which showed particles released from burning candles are extremely small, around seven to eight nanometers.

They are much smaller than those produced by cooking, which are around 80 nanometers, making it easier for them to penetrate deep into the lungs and even enter the bloodstream.   

Candle smoke also contains soot and harmful gases, including nitrogen dioxide and polycyclic aromatic hydrocarbons (PAHs), which are linked to inflammation and cancer risk. This soot can leave black marks on walls, ceilings and nearby surfaces. 

Research experiments found candle emissions can cause biological changes, such as airway irritation, inflammation markers, reduced lung function and cardiovascular effects. 

Vulnerable groups, such as people with asthma, chronic respiratory diseases, children and older adults, are especially sensitive to this indoor pollution.

To avoid these risks, experts recommend using fewer candles or LED alternatives, trimming wicks, avoiding drafts to reduce soot, not burning candles near people with respiratory conditions and ventilating the room afterwards by opening windows.

The particles produced are similar in size and composition to a sort of air pollution called PM2.5, which is made up of microscopic particles from sources like car exhaust, power plants, wildfires and fuel burning. 

These particles are so tiny that they can penetrate deep into lung tissue and even enter the bloodstream where they spark inflammation, constrict blood vessels – raising blood pressure and creating artery-narrowing plaque – and trigger oxidative stress, damaging cells, mitochondria and DNA.

Last month, a team at Emory University in Georgia, USA, determined that PM2.5 contributes to a higher risk of Alzheimer’s, the most common form of dementia.

For every small increase in PM2.5, Alzheimer’s risk rose by nearly nine percent. That might sound modest, but spread across millions of older people, it translates into tens of thousands of additional cases.

The pollution-Alzheimer’s link was strongest in people who had already had a stroke. For them, the same pollution bump pushed Alzheimer’s risk almost 11 percent higher.

Around 900,000 people are currently living with dementia in the UK, a figure expected to rise to more than 1.6 million by 2040. Dementia is the leading cause of death, accounting for more than 74,000 deaths a year.

An estimated 6.7 million Americans aged 65 and over are living with dementia, including Alzheimer’s disease.

This is projected to reach nearly 14 million by 2060, with around 120,000 deaths a year attributed to Alzheimer’s alone.