Burning a scented candle to fill the room with smells of gingerbread, cinnamon and pine may put you in the Christmas spirit, but it could be detrimental to your health.
A study has revealed burning candles has a significant effect on indoor air quality — and it could be worse for your lungs than inhaling passive smoke.
That’s because as candles burn, they produce a complex mix of chemicals and particulate matter, including toxic gases like carbon monoxide, sulfur dioxide, and oxides of nitrogen.
Products like scented candles and incense sticks can also produce volatile organic compounds (VOCs).
Together, inhaling these substances can cause coughing, sneezing and eye irritation and worsen asthma symptoms.
But in the long-term, this indoor pollution can also increase the risk of heart disease, lung cancer and chronic bronchitis, Dr Asit Kumar Mishra, at the University College Cork and Dr Marie Coggins at the University of Galway wrote in The Conversation.
Burning scented candles could cause fine particle concentrations — which can trigger lung damage when inhaled — to increase to 15 times the limits prescribed by the World Health Organisation.
The study, published in the journal Indoor Environments, measured the air quality of 14 homes in Galway in Ireland, both 24 hours before and 24 hours after making changes to improve the house’s energy efficiency.
Burning scented candles produces a complex mix of chemicals and particulate matter, including toxic gases like carbon monoxide, sulfur dioxide, and oxides of nitrogen
In each house, researchers measured the concentrations of five pollutants including CO2 and pollutant particles smaller than 2.5 micrometers, also known as PM2.5, which can easily enter into the lungs, as well as the temperature and the humidity in two rooms.
PM2.5 are soot particles in the air invisible to the human eye that can enter into blood and penetrate deep into the lung. They can be emitted by vehicle engines, wood burning and smoking.
In each room scientists placed pollution-measuring devices a metre away from the floor and sources of pollution and ventilation (such as windows and vents).
During this time occupants were asked to document typical household activities and their heating and ventilation methods such as, when they were cooking, opening windows, burning candles, and cleaning.
The results revealed activities like burning candles, smoking and blocking wall vents can be detrimental to indoor air quality with levels of PM2.5 and CO2 increasing.
PM2.5 particles are thought to cause inflammation in the lungs that can activate dormant, harmfu l cells, leading to cancer-causing genetic mutations.
The International Agency for Research on Cancer (IARC) noted particulate matter PM 2.5 as a Group 1 carcinogen in 2013, due to evidence linking the pollutant to lung cancer.
The study also revealed that if equal weights of cigarettes and incense sticks are burned, the incense sticks produce about four times as much particulate matter as the cigarettes.
In non-smoking households, a candle can be the major source of pollution and introduce ultra-fine particles into the air, with a flickering flame producing more larger particles and increasing the emission of black carbon.
Burning scented candles in small bathrooms or bedrooms exposes occupants to a higher concentration of pollutants, the study found.
In poorly ventilated rooms, researchers found there were higher concentrations of pollutants like formaldehyde — a colorless strong smelling chemical — at levels that can cause upper airway irritation.
In fact, scented candles can be even worse for our health and may produce more fine particles than unscented ones.
But it’s almost impossible to know which chemicals you are releasing into your home when burning a scented candle, with just 10 per cent of ingredients disclosed on the packaging, according to Dr Mishra and Dr Coggins.
That’s because manufactures of scented candles in the US and EU are not obligated to disclose all the substances used in their products.
Nitrogen oxides — which is also emitted from cars — are the main pollutant produced from scented candles and can damage the lungs and airways.
Even some of the organic compounds emitted by home fragrance products, such as benzene, phthalates and formaldehyde may cause cancer, according to the American Lung Association.
In the short term, exposure to these pollutants has been shown to reduce cognitive function, while chronic exposure to incense smoke has also been linked to decline in cognitive function, according to a 2020 study published in the journal Nature.
Researchers also warn that opting for candles made with natural ingredients might not protect you from harmful effects.
Some of the natural chemicals emitted can react with ozone in room air, producing potentially toxic byproducts.
Burning candles in a larger room with open windows may help reduce the harmful effects, the experts advised — but they added more research is needed to understand the full health risks.
