Ah, that new car smell. That leathery, plastic-y aroma can feel like the height of luxury. And you’re about to be the first person to make a real butt imprint on that seat! But this smell comes with a catch. Some of the compounds that make a new car smell fancy have also been known to cause cancer under some conditions. Manufacturers are expected to test how many of these compounds are floating in and around their vehicles, to make sure they’re at safe levels. But buckle up: research suggests these tests might have left out some variables. Like the Sun. And the fact that vehicles spend a lot of time outside.
The molecules that make “eau de new car” belong to a category called volatile organic compounds, or VOCs. In general, VOCs are everywhere: they’re in nail polish remover, they’re in Grandma’s antique wood furniture. They’re in leaves, you name it. And in terms of health effects, they’re a mixed bag. Some have little to no known effects on human health, and some should really stay out of your lungs. When something releases VOCs, it’s called off-gassing, and how big of a deal this is comes down to what compounds are doing it, and in what quantities.
In vehicles, off-gassing comes from things like glue, paint, upholstery, and all the plastic keeping you on the road. Since new vehicles haven’t had a chance to air out, they tend to off-gas more. And the list of VOCs that have been detected in them is about as long as a drug store receipt. Studies have found anywhere from 30 to more than 250 VOCs in vehicles, and some common ones include styrene, acetaldehyde, benzene, and formaldehyde. Again, different VOCs have different potential health effects. But the four I just mentioned are all carcinogens.
Now, this doesn’t mean they definitely cause cancer. Labels like these come from the International Agency for Research on Cancer, and focus on how strong the evidence is that something could cause cancer in the right conditions. For instance, the formaldehyde and benzene in new car smell are Class I carcinogens, or known carcinogens. This means there’s strong evidence that they can cause cancer. Meanwhile, styrene and acetaldehyde are Class II carcinogens. The evidence for these compounds isn’t as conclusive as it is for the stuff in Class I.
But neither of these class labels say anything about how these carcinogens affect your personal risk of getting cancer. There’s a lot more that goes into that. But remember, there are two parts to figuring out if the VOCs in new car smell are a health risk: the compounds, and how much of them there are. I mean, anything can be dangerous in large enough amounts, including oxygen, and water, and even my cat, Huckleberry. He is so fluffy, but at what cost?
So, car manufacturers are expected to figure out how many of these molecules are usually floating around in their vehicles. Different countries and companies have different standards for emissions and how they should be tested. But to give an example: one international organization requires new cars to sit in a chamber at about room temperature, while researchers monitor off-gassing. If the VOC levels are below safety thresholds, the car is good to go.
Except… if you’ve ever gotten into a car on a sunny day and scorched your legs on the fake leather seat, you know cars don’t live in room-temperature bubbles. And unsurprisingly, field studies have found that VOC emissions can change with the weather. Most studies have focused on the air temperature inside vehicles. And they’ve found that when air temperatures were higher, so were VOC levels. For instance, in a 2020 study done in China, levels of some VOCs could be more than 100 times higher in the summer than the winter. But you know how sometimes the air inside a car is just kind of warm, while the dashboard is hot enough to cook a breakfast burrito? Researchers have noticed that, too. In a 2023 paper, scientists focused on surface temperatures inside a vehicle rather than air temperature. After parking a new car outside for 12 days in the summer and taking measurements, they found that the formaldehyde and acetaldehyde levels were 35% and 60% higher than the national standard, respectively. Even on cloudy days, the acetaldehyde levels exceeded the limit by about 20%. Although this was only one car, the researchers calculated that at these levels, the total amount of VOCs implied a high cancer risk for drivers. This was not the only study to come to this conclusion; a 2021 paper from the U.S. analyzed more than two dozen studies about vehicle VOCs and found that formaldehyde and benzene levels were too high for California’s standards. This resulted in over 60% of local commuters having a 10% chance of being at a higher risk of developing cancer.
The time it takes for VOC levels to drop depends on the situation. A 2020 study monitored VOC levels in a new vehicle for almost two years and found that the peak level of total VOCs had dropped almost 25% by the vehicle’s second summer. However, they also found that for certain molecules, the off-gassing rates didn’t decrease with time, including aldehydes. Therefore, buying a used car doesn’t completely solve the problem, but it does help. Additionally, informing car manufacturers and regulatory agencies about these studies can lead to the use of different materials in vehicles.
When considering buying a vehicle, it may be worth picking an older model that’s had a chance to air out. Thanks to our supporters on Patreon, we have the ability to research and use different materials in our vehicles. To join our proverbial pit crew, head on over to Patreon.com/SciShow for all kinds of perks.