That “new car smell” may come from toxic chemicals, according to new research.

A new study suggests that new car smell comes from toxic chemicals off-gassing in a car's interior, like brominated flame retardants (BFRs), chromium, and lead. In all, researchers identified more than 275 different chemicals in vehicle interiors, including those associated with birth defects, impaired learning, liver problems, and cancer.

The 2012 new vehicle study from the nonprofit Ecology Center analyzed the chemical content of more than 200 new cars for its top 10 healthy and unhealthy car interiors. The higher the vehicle rating in the study, the higher the level of these chemicals was, based on their testing methods.

At the top of the list for the most healthy car interior is the 2012 Honda Civic. Researchers say it earned strong marks for not having any bromine-based flame retardants, while boasting polyvinyl chloride (PVC)-free interior fabrics and trim, and low levels of heavy metals.

At the bottom of the list are the 2011 Mitsubishi Outlander Sport and 2011 Chrysler 200 SC, which both had scores in the “high” range. For example, the Mitsubishi Outlander had bromine and antimony-based flame retardants in seating and other areas, chromium-treated leather, and lead in seating materials.

Top 10 Healthy Car Interiors

Top 10 Unhealthy Car Interiors

(Worst at bottom)

What the Ratings Mean

Researchers say that immediately after delivery, new cars have unusually high concentrations of a variety of chemicals, hence that “new car smell.”

In their study, the interiors of more than 200 cars from the 2011-2012 model year were analyzed using a portable X-ray Fluorescence (XRF) analyzer. The analyzer detects chemical elements such as lead, cadmium, chlorine, arsenic, mercury, tin, and antimony.

Common areas checked in the car interiors were seats, arm rests, steering wheels, door trim, and shift knobs, among others.

Researchers say the elemental composition of the materials reveals the presence of potentially hazardous chemicals, such as BFRs, PVC, and possibly phthalate plastics. They say car interiors are like chemical reactors, with temperatures reaching extremes of up to 192 F. These high temperatures can increase the concentration of volatile compounds in the car and speed the breakdown of materials.

Exposure to toxic chemicals can be high indoors and in enclosed spaces like a car interior. Drivers are exposed to these chemicals by breathing and contact with dust.

The EPA says indoor air pollution is one of the top environmental threats to public health, since Americans spend 90% of their time indoors. Next to homes and offices, Americans spend the most time in automobiles, an average of one-and-a-half hours per day.

Rating the Automakers

Overall, researchers say vehicle ratings are improving thanks to the reduction in the use of PVC and bromine-based flame retardants by some automakers.

They say the top-rated automaker for healthy interiors in 2012 was Honda and has been since it started testing in 2007. Hyundai-Kia has been the lowest-ranked manufacturer for the last two years.

German automaker VW, along with Mitsubishi and Ford, earned the title of most-improved automakers. Their scores improved by 30% to 42% from the 2009-2010 model year to the 2011-2012 model year.

Daimler AG and Volvo were the only two automakers with declining average scores, -29% and -13%, respectively.

For a complete list of ratings, see www.HealthyStuff.org.