Questions about the toxicity of new car smell aren't new. Neither are studies aimed at determining whether it's a problem you should be seriously worried about. Probably the most recent of these studies was conducted in February of 2012 by a non-profit group called the Ecology Center. Their "Model Year 2011/2012 Guide to New Vehicles" (which you can download in PDF format here) is unequivocal on the issue: "[T]hese chemicals [in new car smell] can be harmful when inhaled or ingested and may lead to severe health impacts such as birth defects, learning disabilities and cancer. Since the average American spends more than 1.5 hours in a car every day, toxic chemical exposure inside vehicles is becoming a major source of potential indoor air pollution." Whoa! That's enough to make you want to wear a gas mask until your car's old enough for the warranty to expire! But before you decide to buy only used cars for the rest of your driving life, they add that "some cars are better than others. Toxic chemicals are not required to make indoor auto parts, and some manufacturers have begun to phase them out."
Okay, guys, let's name some names. Which cars does the Ecology Center believe have the healthiest interiors? Their top five picks, starting with the healthiest, are the 2012 Honda Civic, 2011 Toyota Prius, the 2011 Honda CR-Z, the 2011 Nissan Cube and the 2012 Acura RDX. Check their PDF to see the rest of the top ten. The two cars with the least healthy interiors, according to the Ecology Center, are the 2011 Chrysler 200 S and, in last place, the 2011 Mitsubishi Outlander Sport. Honda wins as having the line of cars with the healthiest interiors overall. The report concentrates on the presence of bromine (used in flame retardants), chlorine, and lead, grouping other volatile organic chemicals in a single category in their rankings. The report includes a list of hundreds of popular cars manufactured from 2006 to the present and lists the amount of each of these substances present in each car's interior.
Fortunately, a lot of the volatile chemicals in a car's interior go away over time -- that's why they call it "new car smell" -- but they don't go away completely and they can come back on hot days when the higher temperatures increase the rate of outgassing. One thing you can do to combat this process on hot days is to roll down the windows rather than using the air conditioner, letting fresh air circulate into the car and releasing the volatile compounds into the air outside (which isn't necessarily good for the air outside, but it's certainly better than being closed up in a car full of toxic fumes). You can also park your car in the shade, so it will stay reasonably cool.
Not all studies done over the years have agreed that new car smell is a danger to automobile occupants. A 2007 study conducted at the Technical University of Munich in Germany concluded that the chemical compounds released inside a car might at worst exacerbate allergies, but don't pose any other significant threats to human health. The study was conducted by collecting air samples from the interiors of new cars and three-year-old cars placed under 14,000 watts of lights, which generated interior temperatures up to 150-degree Fahrenheit (65.6-degree Celsius), a lot hotter than the average car is likely to become under ordinary conditions. They then exposed human, mouse and hamster cells to these samples to look for toxic effects. None were found. The researchers concluded that new car smell isn't toxic. However, the researchers also admitted that if the air inside an office building were found to have the same chemical content as the air samples found in the cars, the building would be declared to have sick-building syndrome and the workers would be sent home until it had been cured.
So in a sense both studies agree: Automobile interiors contain poisonous chemicals. But the Ecology Center feels that these chemicals represent a health threat to occupants and the German researchers do not. In the end, you'll just have to choose which study you want to take seriously. And maybe roll down your windows a bit more than you usually do to let the bad air out.