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. [♪ INTRO] 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 one 2023 paper, scientists  focused not on air temperature, but surface temperatures inside a vehicle. Researchers in China parked a new car outside for 12 days in the summer and took  measurements as the weather changed. They found that at their highest, the  formaldehyde and acetaldehyde levels were about 35% and 60% higher than  the national standard, respectively.

Even on a cloudy day, acetaldehyde  levels exceeded the limit by about 20%. Now, this is just one car,  so it could be an outlier. But at least in this case, the researchers’  calculated that at these levels, the total amount of VOCs imply  a high cancer risk for drivers.

And this isn’t the only study  to come to that conclusion. A 2021 paper from the U. S.  didn’t focus on vehicles’ ages, but after analyzing more than two  dozen studies about vehicle VOCs, they still concluded that  formaldehyde and benzene levels were too high for California’s standards.

Because of this, they found  that over 60% of local commuters had a 10% chance of being at a  higher risk of developing cancer. Again, that doesn’t say anything  about anyone’s personal risk, just that the overall risk is higher. So, how long does it take for VOC levels to drop?

If you’re currently Googling “new car  trade-ins” in a different tab, maybe hold on. Because it depends. A study published in 2020 monitored VOC levels in a new vehicle for almost two years.

They used a detection method that didn’t  pick up formaldehyde, so no data there. But for the compounds they did measure,  they found that the peak level of total VOCs had dropped almost 25%  by the vehicle’s second summer. Unfortunately, they also found  that for certain molecules, the off-gassing rates didn’t  really decrease with time.

And that includes aldehydes, the  family acetaldehyde is part of. So buying a used car doesn’t  solve the whole problem. But it seems to help, as would leaving  the windows open whenever possible.

And on a larger scale, it might  be encouraging to know that studies like this aren’t just for consumers. They also inform car manufacturers  and regulatory agencies, who have the power to research and use  different materials in their vehicles. Ultimately, there can be a lot of  good that comes with a new car, especially as they become more efficient.

So, if you have the ability to buy any vehicle  sitting there looking pretty on the lot, there’s a lot to consider…including  if it’s worth picking an older model that’s had a chance to air out. Thanks for watching this episode of SciShow, and thanks especially to  our supporters on Patreon. Y’all keep our tires filled with air,  our windshield wiper fluid topped up, our batteries charged…you  know, all the car metaphors.

If you’d like to join our proverbial pit  crew, head on over to Patreon.com/SciShow. We’ve got all kinds of perks, from access to a not-so-secret bonus podcast to  behind the scenes clips, and more! [♪ OUTRO]