Candles add light and beauty and sense of ritual to almost any occasion. For many of us they are the ultimate statement of holistic living.
For these reasons it’s hard to imagine that there could be anything inherently unhealthy about burning candles and yet mounting evidence suggests that their bright beauty can sometimes hide several toxic secrets.
As the candle burns, it releases largely invisible but dirty soot containing microscopic particles light enough to remain suspended on the air for a long time, and small enough to be easily absorbed into the body once inhaled. If your candle contains heavy metals it will most certainly add to the amount of these pollutants in your home.
In one 2000 study researchers from the University of Michigan School of Public Health purchased a range of candles made in the United States, Mexico and China and examined the amount of lead they emitted on burning as well as the amounts that lingered in the air in an enclosed space, such as a room measuring 12 feet by 12 feet and 10 feet high, after one hour and then again for five hours.
Scary results showed that lead emission rates for the candles ranged between 0.5 and 327 micrograms (mcg) per hour.
After burning the candle for one hour, the lead levels in the air of an enclosed space were estimated to range from 0.04 to 13.1 mcg per cubic meter (‘safe’ levels, as defined by the US Environmental Protection Agency are 1.5 mcg per cubic meter); after five hours they were 0.21 to 65.3 mcg per cubic meter.
Research by the Environmental Protection Agency in 2001 found that burning a candle with multiple wicks or multiple candles can lead to high levels of pollutants indoors. Scented candles, so popular for the romantic ambience they lend to a room, are more likely to give off more of this soot than unscented ones.
The core of the problem
The greatest danger lurks at the heart of the candle. The purpose of a wick is to draw wax to fuel the flame. In candle making, different types of wick are used for different purposes and these can be divided into two general categories: cored and non-cored wicks.
Non-cored wicks are generally made of a braided or twisted fibre (usually cotton), and are considered to be the safest to burn. Cored wicks also use cotton but it is wrapped around a paper or metal core that gives it support in candles that melt easily (for instance, some container candles).
Wicks with a metal core also burn at a higher temperature, useful when the candle is made of a wax that requires a high temperature to melt. Among the metals used in candle wicking are lead and cadmium, as well as zinc and tin.
Lead and cadmium
The first two are particularly worrying since both lead and cadmium build up slowly in the body and can remain there for decades, even after sources of exposure have been eliminated. Lead, can adversely affect the central nervous system (brain and spinal cord), the heart, red blood cells, and kidneys. Chronic exposure in adults is associated with endocrine and reproductive problems. High body loads can cause deficiency in calcium, iron, and zinc.
Children are particularly at risk since compared to adults, more of the lead they ingest stays in their bodies. Lead exposure has also been linked depressed intelligence and cause behavioural problems in children.
Both the EPA and the International Agency for Research on Cancer (IARC) say that inhaled cadmium is carcinogenic to humans. Over time it can also have a debilitating effect on the liver and kidneys, bones and testes as well as the immune and cardiovascular systems.
Cadmium is also considered an endocrine disrupter. It has been shown to cause birth defects in mammals and has been linked with both stillbirth and low birth weight. Men exposed to high levels of cadmium in their work are at greater risk of prostate cancer. (Here’s more on the adverse health effects of heavy metals)
More than 40 years ago, the US candle making industry vowed to remove lead from their products. Nevertheless it took until April 2003 for the US Consumer Product Safety Commission to finally ban the sale and import of candles with lead wicks in the US. Other countries, including the UK, have yet to follow suit. There is no way to distinguish lead-containing wicks from safe ones nor are candle manufacturers obliged to state of product labels what their wicks contain.
Other risky ingredients
The release of toxic metals, in any quantity, into the air is worrying. But candles contain a complex mix of other unseen and unlabelled ingredients and these also add to the atmospheric pollution they create.
One of these is paraffin. Made from petroleum wastes this is the most common type of candle wax. From the manufacturers’ point of view it is cheap and easy to work, has an appealing translucence and is slow burning. Gel waxes have recently become popular because of their crystal clarity and ability to hold colour and fragrance. These are basically petroleum oil turned to jelly, and need to be used in a container (and often with a reinforced wick) because the wax is very soft. Both are made from petroleum, a non-renewable resource. Both also produce smoke and soot.
In 2005 the American Lung Association issued a warning that paraffin candles can emit a frightening range of known carcinogens including acetaldehyde, formaldehyde, acrolein, acetone, benzene, 2-butanone, carbon disulfide, carbon tetrachloride, creosol, chlorobenzene carbon monoxide, cyclopentene, ethylbenzene, phenol, styrene tetrachloroethene, toluene, trichloroethene and xylene as among the other toxins.
In 2009 a study by the American Chemical Society concluded that paraffin based candles were an unrecognised source of carcinogens such as toluene and benzene in the air at home. Soya-based candles did not emit these poisons.
And of course cotton wicks, unless they are certified organic, are likely to be made from GMO cotton.
Catching the scent
The fragrance oils added to candle wax are generally synthetic and based on petroleum products. These are the same synthetic fragrances added to you cosmetics, soaps, detergents and air fresheners. In addition to the fragrance oil itself, the candle will contain ‘fixatives’ that allow the oils to blend with wax and give off an aroma when heated.
There is nothing vaguely romantic about synthetic perfumes. Their ingredients include industrial solvent such as benzene derivatives, aldehydes, and many other known toxins and sensitisers capable of causing cancer, birth defects, and central nervous system disorders (see the report by the US Committee on Science and Technology, Neurotoxins: At Home and the Workplace, US House of Representatives, Report No. 99-827, Sept. 16, 1986). Some like acetone, ethanol and ethyl acetate and methylene chloride are classified by the EPA as “hazardous waste”.
Perfumes, including perfume strips included in magazines, can also induce a range of other toxic effects. These can include asthma and skin disorders.
Unfortunately, it can be difficult – but not impossible – to produce a candle using natural essential oils. Good quality essential oils are usually more expensive than synthetic fragrances and so not suitable for cheap production line candles, and may not blend well with conventional candle wax.
In addition to synthetic fragrances many types of candles contain synthetic colours. Oil-soluble aniline (coal tar) dyes give colour to a candle throughout. Pigments are usually used on the exterior of candles to give a deeper colour than can be achieved with dyes. The safety of colours used in candles depends largely on the ingredients of the dye however most synthetic dyes will give of some unsafe particles on burning.
While many consumers would presume that candles bought from big name stores might be less likely to contain traces of toxic metals this is not necessarily the case.
Choosing and using candles safely
How ‘cleanly’ a candle burns, depends on many things including the type of wax it is made of, and whether it is perfumed and coloured. A wick that is too large will flare and burn less cleanly than a properly trimmed wick. A flaring, smoky flame will be emitting undesirable particulate matter into the air no matter what the wick is made from.
It is almost impossible for most consumers to tell the difference between candles with metal containing wicks and those which are free from toxic metals and there is currently no legislation in the UK to stop such candles being sold.
If you want the glow of candlelight in your home with a minimum of toxic emissions consider the following measures:
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