How Your Cosy Candle Could Be Damaging Your Health
New research has uncovered that burning candles, a common practice for creating a warm and inviting atmosphere, produces a group of chemicals associated with cancer. This finding highlights potential hidden dangers in our homes, particularly during the winter months when candle use peaks.
The Prevalence of Candle Burning
In Denmark, for instance, around 75 per cent of the population burns candles two or more times a week, with 34 per cent using them daily in winter. Denmark is often cited as having the highest per-capita candle consumption in Europe, with Danes burning approximately 5.8kg of candle wax per person annually—equivalent to about six bags of sugar.
Despite their aesthetic appeal, studies indicate that burning candles is one of the most significant sources of indoor air pollution. This is due to the emission of a large number of ultrafine particles during combustion. These particles are invisible to the human eye, over a thousand times thinner than a human hair, and can remain airborne for extended periods. When candles are extinguished, the concentration of these particles, including soot, increases even further.
Candles Versus Cooking: A Comparative Analysis
Experiments conducted in controlled climate chambers at Aarhus University examined how indoor air is affected by both burning candles and cooking pork in an oven. While cooking, especially frying, is known to emit high concentrations of particles from combustion processes—which are among the most harmful to human health—less was understood about the impact of candle emissions.
The research revealed that both candles and cooking emit high levels of particles, but the number from candles was much higher. More notably, there was a stark difference in particle size: cooking produced particles about 80 nanometers wide, whereas candles generated particles around seven to eight nanometers in size. These smaller particles are much easier for our lungs to inhale.
Additionally, chemical compounds in the air were measured, showing that burning candles release not only soot particles but also gases such as nitrogen dioxide and polycyclic aromatic hydrocarbons (PAHs). PAHs are a group of chemicals linked to inflammation and even cancer.
Health Implications of Ultrafine Particles
Ultrafine particles are a major health concern because they are easily inhaled into the lungs but excreted from the body very slowly. Due to their minuscule size, particles from candles can penetrate deep into the alveoli—the smallest airways—and may even enter the bloodstream, potentially reaching organs like the heart and brain.
Remarkably, the particles formed during candle burning are similar in size and composition to those found in diesel exhausts, which have been associated with increased mortality rates from lung and cardiovascular diseases.
The study also investigated effects on young adults with mild asthma, finding subtle but measurable biological changes after exposure to candle emissions. Markers of airway and blood inflammation were altered, and participants reported irritation and discomfort. Other research among healthy adults has observed small decreases in lung function, changes in arterial stiffness and heart rate, and reduced cognitive function following exposure.
Vulnerable Populations and Indoor Air Quality
Individuals with chronic conditions such as asthma or chronic obstructive pulmonary disease are far more sensitive to particulate air pollution. Since they already have chronically inflamed airways, even relatively low levels of pollution—including particles from burning candles—can trigger symptoms.
Children, older adults, and people with chronic illnesses are also particularly vulnerable due to immature lungs or weakened immune systems. For anyone with respiratory conditions, indoor air quality is not a minor detail but a crucial factor in managing day-to-day symptoms and long-term health.
Practical Steps for a Healthier Indoor Environment
While burning candles can affect everyone's health, not just those with lung diseases, there are simple measures to mitigate risks. Consider using LED candles or limiting the number of candles lit at once. Place candles away from drafts to prevent flickering flames, which produce more soot and smoke, and trim wicks to reduce soot formation. Importantly, never burn candles near individuals with respiratory diseases.
Most crucially, air out the room by opening windows after candle use. These steps can significantly reduce particle levels, helping to maintain a healthy indoor climate while still enjoying cosy moments.
