As someone who always loved lighting candles throughout most of my life, I never thought twice about whether those candles could possibly be affecting my health. In fact, I basically associated all candles with wellness, and I often used them as a kind of self-care. Any time I needed to wind down after a hectic day or just wanted to create a calming sanctuary in my home without much effort, I lit a candle or two. Trying to find non-toxic candles never crossed my mind.
As I’ve learned recently, the answer to the question of whether candles are toxic or not is not a simple yes or no. In short, not all candles are created equal.
In this article, I’ll be exploring the research behind candles and air quality and what makes candles toxic. I’ll also be discussing how to find the best mostly non-toxic candles so you can keep your home safe and healthy!
If you want to skip to reading some quick tips when shopping for non-toxic candles and would like examples of mostly non-toxic candle brands, read How to Choose the Best Non-Toxic Candles for a Healthier Home.
A Closer Look at the Chemicals in Candles
Colorful, scented candles can seem fun and harmless. But in reality, they can be problematic when it comes to maintaining indoor air quality. When I sat down to further research whether candles were toxic or not, I came across some interesting information about chemicals and emissions that I am eager to share with you.
Since all candles are by nature a combustion product due to being a burning agent, it is pretty much inevitable that they will contribute to some degree to air pollution. After-all, they do emit smoke and soot as we can easily see. However, as mentioned above, not all candles are created equal, and I wouldn’t necessarily throw out all my candles based on that alone.
Based on what certain candles are made of, they can be more or less harmful. Additionally, where they are burned, how they are burned, and for how long can also make a difference. For the purposes of this article, I want to focus on the chemicals involved with candles.
Combustion byproducts of candles, depending on the specific ingredients used to make them, can include:
- Volatile organic compounds (VOCs)
- Polycyclic aromatic hydrocarbons (PAHs)
- Benzo[a]pyrene (BaP), found in coal tar, tobacco, crude oil, and grilled meats, and a known carcinogen
- BTEX
- Aldehydes
- Formaldehyde (a respiratory irritant and known carcinogen in animal studies)
- Acrolein
- Polycyclic aromatic hydrocarbons (PAHs)
- Particulate matter (fine and ultra-fine particles)
I’m going to break down information about VOCs and particulate matter in more depth so you can understand why they are important.
1. Volatile Organic Compounds (VOCs)
If you have heard of formaldehyde, benzene, and toluene, these are some common examples of volatile organic compounds. I found this really comprehensive list of VOCs on the AQT website if you’re interested in seeing more examples.
What exactly are VOCs? In a nutshell, VOCs are toxic chemicals that are lighter than air and unstable at room temperature. When looking at VOCs from a physical science perspective, they:
- vaporize easily (due to having high vapor pressure)
- can stay in the air for long periods of time
- can travel in the air long distances
- do not dissolve well in water (due to having low water solubility)
- do not break down easily
They are in products we use everyday, ranging from flame retardants and paint thinners to various cosmetics. Unfortunately, despite being so common, research has shown that VOCs can have negative effects on our health.
Major Examples of VOCs in Candles
Some of the VOCs emitted from candles include benzo[a]pyrene (BaP), toulene, benzene, formaldehyde, and acrolein.
Toluene is a BTEX1 VOC used in paint thinners and adhesives. It is known to potentially cause irritation to eyes, nose, throat, and skin as well as headaches, dizziness, anxiety and confusion in low-ventilated spaces as well as neurological harm.
Benzene is a gas that is released from forest fires, burning coal or oil, and volcano eruptions. About 90% of benzene, however, is emitted from smoking. Benzene exposure has been linked to cancers of the blood like leukemia.
Formaldehyde is a respiratory irritant and a known carcinogen in animal studies.
Acrolein is another aldehyde.
One study found that long-term concentrations of acrolein and the benzo[a]pyrene (BaP) from candle emissions exceeded air quality standards set by the WHO and the U.S. EPA (Salthammer, 2021).
For benzo[a]pyrene (BaP), an indicator for incomplete combustion processes, and acrolein, the long-term concentrations set by WHO and US EPA were “exceeded or partly exceeded.”
The amount of candle emissions are considered pretty small. However, the fact that VOCs do not break down easily and can accumulate over long stretches of time is something I find especially concerning.
When it comes to the effects of candles on indoor air pollution, the size of the negative effects depends largely on:
- The concentration of VOCs in the air (this increases with poor ventilation especially in small spaces)
- How long the VOC exposure is
Short-term VOC exposure in high concentrations can result in eye, nose and throat irritation, headaches, nausea or vomiting, dizziness or worsening asthma. Even more troubling, and more relevant to candles, is that frequent exposure to VOCs for many years at even low levels can ultimately lead to damage to the liver and kidney as well as cancer.
On their own, candles are seen as low risk since they emit VOCs in small amounts below indoor air quality regulatory standards. and actually tend to emit fewer VOCs than other common household products. That being said, something to consider is how candles contribute to VOC accumulation in your home, overall. Remember how I mentioned VOCs don’t break down easily and linger for long periods of time? Well, apply this to all the VOCs you are using in your home via everyday products, and something small can potentially end up becoming a big issue.
It is important to note that VOCs are also naturally produced by animals, plants and microorganisms. But the issues we are seeing on the rise are likely due to the explosion of man-made creations that emit VOCs in modern society. This paired with the general issue of increasing toxicity around us and the added problem of indoor air pollution make even the small amount of VOCs from candles cause for concern.
2. Particulate Matter (Fine and Ultrafine Particles)
I’ll be honest with you. Until I actually dove in and did research on candle chemicals, I had never heard of particulate matter, better yet fine (PM2.5) and ultrafine (UFP) particles. But here is what I discovered when I looked into it and read various articles and research about it.
Particulate matter (PM) is a mixture of various chemicals and other natural components (e.g., dust, microogranisms) that are a big component of air pollution. They can range in size, including coarse (PM10), fine (PM2.5), and ultrafine (PM0.1 or UFP) and can contribute to severe negative health effects regardless of size. Not only do they make existing diseases worse, but they also increase the occurrence and mortality of many diseases, including respiratory and cardiovascular diseases. It is important to note that the toxicity of UFP increases as their size decreases and surface area increases (Pope et al., 2002). Given that PM2.5 fine particles can cause so much damage, ultrafine particles (UFP) are even more dangerous due to their smaller size.
Interestingly, indoor activities like cooking, vacuuming, burning candles, and smoking inside are the biggest contributors of UFP (Marval & Tronville, 2022). Although UFPs usually enter the body via the lungs, they can translocate to other organs in the body via the alveoli and parenchyma and make their way to the bloodstream and heart. Ultimately, they can cause damage to various parts of the body including the respiratory system, cardiovascular system, and all organs. UFPs can predispose people to ischemic cardiovascular disease and hypertension. UFPs are also linked to diabetes and cancer. Not only that, they can cause autonomic and cerebral dysfunction if they make their way up the olfactory nerves to the brain (Hong & Gee, 2020; Brook et al., 2010).
Needless to say, UFPs are just really bad news. And given that they are already occurring as a result of everyday activities like cooking and vacuuming, I personally wouldn’t really want to add fuel to the fire.
Bringing this back to candles specifically, one study found that within the first 30-60 minutes, there was a significant increase in the concentration of UFPs in a candle emission test chamber. Even so, the concentrations of various emissions including UFPs (both short-term and long-term) were at or below indoor air safety standards (Salthammer et al., 2021).
Again, you want to consider these conclusions in context. Sure, the results in a controlled study confirm they meet safety standards. That is good news. But you’d want to ask further relevant questions such as:
- How long are the candles typically burned?
- How often are candles used in a given space?
- How many candles are used in that space?
- How big is the space in which the candles are burning?
- What happens to those candle emissions over time? For example, do the emissions dissolve? Do they accumulate?
- What other emissions are in the space? What is the total day-to-day emission release from everything in that space (e.g., from vacuuming, cooking, aerosol use, etc.)?
- Are there mechanisms in place that help ventilate the space adequately?
- What pre-existing health issues do the people and pets experience already or are prone to?
Once you start asking all of these questions, it becomes clear that “safety standards” are almost subjective in a way. To me, the fact that there are VOC and UFP emissions at all are cause for concern.
In any case, the different ingredients of a candle influence its toxicity. Next, I’ll be going through some key components of a candle and discussing what makes it more or less toxic.
What Parts of a Candle Can Be Toxic?
When trying to determine the toxicity of a candle, you’ll want to look at 4 main components:
- Wax
- Fragrance
- Coloring
- Wick
1. Wax
The Problem with Paraffin Wax
When looking at a candle to decide if it is more or less toxic, you’ll want to examine the wax. The general rule is that you want to avoid paraffin wax! Unfortunately, the majority of mass-produced, conventional candles are made from paraffin wax, which is a petroleum byproduct.
One study by Rezaei et al. (2002) found that compared to soy wax candles, paraffin candles produced much more soot. The soy wax candles, however, produced little or no soot. They also burned at a slower rate and required less air. Rezaei also found formaldehyde emissions were higher in paraffin candles compared to soy and beeswax.
Be Aware of Hidden Blends
One thing to note about soy and other natural wax candles is that manufacturers oftentimes say they are selling soy or coconut candles when they are in fact soy blends with paraffin. You’ll want to make sure that the candle you are purchasing is 100% soy or 100% coconut.
The other thing to keep in mind is that pesticides may be in soy products based on how the plants are grown. If you can somehow verify that it is organic, that would be helpful to avoid this issue.
Wax Recommendations
Ultimately, my recommendation for candle wax is to try to find 100% beeswax candles. Locally harvested beeswax is even better. Beeswax is great because it releases fewer emissions.
Some claim that beeswax also has air purification properties from the negative ions it releases that neutralize pollutants. But I wasn’t able to confirm that with any research. If this does turn out to be true, that would be a plus!
I do want to re-emphasize that although some sources say that formaldehyde emissions of paraffin candles are “low and below regulatory concerns”, you want to keep in mind the big picture. How are these emissions contributing to the overall concentration of VOCs and particulate matter in your home when combined with everything else? You’ll also want to keep in mind your own toxic load and health susceptibilities.
2. Fragrance
If I were to tell you the No. 1 thing to avoid in candles if you wanted to eliminate a big chunk of toxicity, I’d tell you to eliminate fragrances.
I know. Fragrances are one of the best things about candles! But here’s why.
Salthammer et al. (2021) found that unscented candles hands down showed the fewest emissions. Compared to scented candles, only traces of combustion byproducts like benzene, toluene, and acetophenone were detected in unscented candles. The researchers found that the majority of individual VOCs detected in scented candles were actually evaporated fragrance materials from the molten wax in addition to fragrance molecules drawn up into the wick.
What’s more is that Ahn et al. (2015) found that even when scented candles were unlit, they still release VOCs into the air! As mentioned before, VOCs can cause many issues including headaches, dizziness, and can even be carcinogens. But something else to be aware of is that synthetic fragrances contain VOCs called phthalates. Phthalates are endocrine-disrupting chemicals linked to a variety of health issues (Wang & Qian, 2021).
Some people say that replacing synthetic fragrances with essential oils like lavender and peppermint is better. However, I was not able to find research to confirm this. It’s unclear if combustion also has a negative effect on essential oils. I would imagine that the quality of the essential oils used would also make a difference.
3. Coloring
You know how candles can be so beautifully colorful and eye-catching? Well those bright, bold, and beautiful colors are oftentimes synthetic dyes that may release toxins when burned.
You’ll want to make sure your candles either use no coloring or natural coloring. Even then, I honestly have unanswered questions about how natural coloring may interact with combustion.
4. Wick
Although most companies have phased out lead-core wicks, some imported candles may still use them. It’s always a good idea to double check! Burning candles with lead wicks can release lead particles into the air. These particles settle onto surfaces, and people and pets can inhale them. Prolonged exposure to lead can affect nearly every organ system in the body
You will want to opt for 100% cotton or wood wicks for a cleaner burn.
Candle Chemistry Conclusion
I hope you found this article helpful! My goal in sharing everything here is to inform readers so that they can make the best decisions for themselves. I like for people to have all of the real, research-based information, not just one biased perspective.
After reading this article, perhaps you will choose not to use candles at all or choose different kinds of candles. Or maybe you’ll even continue buying conventional fragranced, paraffin candles. At the end of the day, what matters most is having the power to make informed decisions for you and those around you.
Ready to Find Non-toxic Candles?
If you are ready to start looking for the best non-toxic candles, read How to Choose the Best Non-Toxic Candles for a Healthier Home for easy tips and recommended brands!
Footnotes
- The BTEX group of VOCs are in their own group since research has shown sufficient evidence that they are cancer-causing. BTEX VOCs include benzene, toluene, ethylbenzene and xylene. ↩︎
Sources
Ahn, J., Kim, K., Kim, Y., & Kim, B. (2015). Characterization of hazardous and odorous volatiles emitted from scented candles before lighting and when lit. Journal of Hazardous Materials, 286, 242–251.
Are Candles Toxic to Indoor Air Quality? (2020, April 28). Minnesota Department of Health.
Benzene and cancer risk. (n.d.). American Cancer Society.
Brazier, Y. (2024, May 13). Health effects of volatile organic compounds.
Brook, R. D., Rajagopalan, S., Pope, C. A., Brook, J. R., Bhatnagar, A., Diez-Roux, A. V., Holguin, F., Hong, Y., Luepker, R. V., Mittleman, M. A., Peters, A., Siscovick, D., Smith, S. C., Whitsel, L., & Kaufman, J. D. (2010). Particulate matter air pollution and cardiovascular disease. Circulation, 121(21), 2331–2378.
Complete list of VOC’s – AQT. (n.d.). AQT.
David, E., & Niculescu, V. (2021). Volatile Organic compounds (VOCs) as environmental pollutants: Occurrence and mitigation using nanomaterials. International Journal of Environmental Research and Public Health, 18(24), 13147.
Hickok, K. (2022, January 27). What is VOC? Facts about volatile organic compounds. livescience.com.
Hong, G., & Jee, Y. (2020). Special issue on ultrafine particles: where are they from and how do they affect us? Experimental & Molecular Medicine, 52(3), 309–310.
The inside story: A guide to indoor air quality | US EPA. (2024, October 22). US EPA. https://www.epa.gov/indoor-air-quality-iaq/inside-story-guide-indoor-air-quality
Marval, J., & Tronville, P. (2022). Ultrafine Particles: A review about their health effects, presence, generation, and measurement in indoor environments. Building & Environment, 216.
Rezaei, K., Wang, T., & Johnson, L. A. (2002). Combustion characteristics of candles made from hydrogenated soybean oil. Journal of the American Oil Chemists Society, 79(8), 803–808.
Salthammer, T., Gu, J., Wientzek, S., Harrington, R., & Thomann, S. (2021). Measurement and evaluation of gaseous and particulate emissions from burning scented and unscented candles. Environment International, 155.
Volatile Organic Compounds in Your Home – MN Dept. of Health. (n.d.).
Wang, Y., & Qian, H. (2021). Phthalates and their impacts on human health. Healthcare, 9(5), 603.
Worried if candles are toxic? (2024, August 29). Cleveland Clinic.
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