What makes a candle smell nice? Perhaps the unexamined answer to this seems obvious. Perhaps you assume vanilla-scented candles contain vanilla, or that candles that smell of sun-dried linen somehow contain linen, but of course this is wishful thinking. In the same way food chemists have upended the ingredients lists of our favourite foods, modern perfumists have synthesised aromas that smell nothing like what they're made from.
Take 4-Hydroxy-3-Ethoxy Benzaldehyde, for example. This synthetic compound is generally perceived as the smell of vanilla in cleaning products, and, sometimes, candles. It's been around for a long time and it's probably quite safe, but manufacturers using this chemical are under no pressure to advertise its presence. In fact, federal agencies in Australia, US, Canada (and to a lesser extent, the UK) all allow chemicals such as these to be ambiguously listed as “parfum” or “fragrance.”
Historically, this has been simply to protect the intellectual property of perfumeries, but some research suggests there is room for concern. For example, a 2010 paper authored by the Environmental Working Group (EWG) studied the contents of 17 everyday perfumes and found an average presence of four suspected hormone disruptors, such as Galaloxlide and Tonalide, and an average of 10 chemicals that had been insufficiently assessed for their long term safety.
Now, before we go off into conspiratorial, anti-vaxxer territory it's worth noting that no scientific body has explicitly found perfumes and scented candles to be poisonous. Rather, it's simply an industry without much regulatory oversight. And it's not very hard to find people who claim their health has been genuinely affected.
For some, like Corinne Segura, simply being around the smallest amount of synthetic perfume can result in a symphony of ailments.
“[After] my first major reaction to incense, I noticed that I could not handle other highly scented products like scented candles, Febreze, or Glade plug-ins," she told us from her home in Vancouver. "One of the most common places I find scented candles is in stores and hotel lobbies. In lobbies, I just start to feel very dizzy. Nauseous. I just want to get out of lobbies as soon as I can.”
Corinne told us that she used to use a lot of incense, but suddenly around the age of 20 she started feeling sick around artificial smells. Ever since then, Corinne tells us she's lived with something she calls “Multiple Chemical Sensitivity (MCS),” which is a relatively unknown condition, resulting in a variety of allergic responses to certain chemicals and smells—each case with its own unique reaction to a unique chemical.
Again, this does all sound somewhat suspicious, but perhaps not if we stop to unpack the chemistry of aromatics.
To create a scent, you need volatile organic compounds, better known as a VOCs. The nature of these chemicals is extremely varied. Many are derived from plants, but just as many are synthetic, and the only thing that really unites them is they all have low boiling points, which means they become gases at room temperature, allowing you to inhale and exclaim "that smells nice!"
Hazardous VOCs aren't usually added to candles, but that sometimes doesn't matter because a candle's flame has the ability to alter the molecule. For example, a naturally occurring chemical called limonene, used in citrus scents, can produce formaldehyde when burned, which is a known carcinogen. So if you light up a perfectly safe lemon-scented candle, you're inadvertently releasing small amounts of very unsafe formaldehyde into the air.
The good news is that scented candles don’t actually emit enough of a dose for an acute toxic response. In fact, formaldehyde is present in many natural products, like wood, apples, and fish. And in fact, just peeling an orange can expose us to more limonene than cleaning products.
But, if we go back to Corinne’s experience, fragranced products exist everywhere and many of them do emit quite a lot of VOCs. And if we consider how much that increases our exposure to VOCs—which are 10 times higher indoors than outdoors according to the EPA—the question changes to: are all these chemicals having a compound effect?
In 2018, the Preventative Medicine Report released a paper written by Dr. Anne Steinemann of the University of Melbourne, and she suggested the answer was yes. Following a 2016 online survey of 1098 Australians, she found that almost a third of the participants admitted to having some kind of chemical sensitivity. This figure is largely similar to Anne’s previous study that found over a quarter of American participants, too, had some kind of chemical sensitivity.
“This is an epidemic,” said Anne Steinemann in 2017, in a press release from the University of Melbourne. “Fragranced products are causing health problems across Australia. The effects can be immediate, severe, and totally disabling. But they can also be subtle, and people may not realise they’re being affected.”
Chemical sensitivities and environmental illnesses, such as MCS, are, much like any other functional disorder, complex and not completely understood. Symptoms range from mild headaches and rashes to bed-ridden debilitation.
But this idea of compounded low-level exposure does have inconsistencies as well as its critics, such as Dr. Pamela Dalton, a psychologist and the principal investigator at Pennsylvania’s Monell Chemical Senses Center for the last 26 years.
“Essentially, there is a threshold for a reaction to the body," she says. "And it’s not clear that these chemicals sequester in the body in any way where they can build out and be at a toxic level. No one, to my knowledge, has ever shown that.
“The large overexposure can have effects acutely that generally dissipate after exposure ends, provided that we’re not talking about a chemical at an acutely toxic level, [but] most of them aren’t.”
Pamela is sympathetic to the experience of MCS, believing that exposure to certain chemicals can affect cerebral blood flow which in turn can cause migraines. Even for her though, there are still unanswered questions. Questions such as how a VOC can elicit an immunological response beyond irritation if they lack the necessary protein; and why there’s currently no investigative procedure that reflects how breathing in a chemical can cross to a different biological system to create something like skin irritation.
One alternate explanation to the sudden onset of these sensitivities is, at least partly, psychological. Such claims, however, are vehemently rejected by the majority of the MCS community, with positions suggesting such an angle is used to routinely dismiss the validity of MCS alongside other functional disorders—as reflected in the criticism over the Netflix documentary Afflicted—which in turn makes treatment, support, and recognition difficult. But while this psychological element is loaded, Pamela suggests that MCS could be a combination of both the physiological and psychological.
“I think there could be a role for both [physiological and psychological causes] but purely in the exacerbation. It's really hard to imagine that somebody would have the exact same reaction to hundreds of structurally unrelated chemicals, given that nothing has ever been shown to work that way in a biological mechanism. That’s why I think there’s room for both.”
Thomas Dantoft, the project manager of the Danish Study of Functional Disorders (DanFunD)—the world’s largest general population-based study of functional disorders like MCS, fibromyalgia, and chronic fatigue syndrome—shares a similar perspective: that until we have long-lasting and repeated studies showing conclusive causation, rather than association, on these relatively recent conditions, anything is possible.
“There’s no evidence for one side,” says Thomas, before adding “you have to remember that there’s a huge difference between causation and association. We have seen a lot of association in terms of psychology, biology, and the neurology of MCS, but these findings are mostly based on case-controlled studies; cross-sectional designs that can only give associations. It doesn’t give any evidence for causation.”
So, in the end, it's kind of hard to draw the line. Maybe scented candles are surreptitiously sowing a health crisis, or maybe some people just get paranoid around chemicals. In any case, maybe it's a good idea to provide consumers with detailed ingredients lists for things designed to be inhaled, and not just for the things designed to be ingested.
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