So, what chemicals are inside the average car?

There are dozens and dozens of chemicals, actually. The worst offenders are vinyl, flame-retardants and lead, all of which are very unhealthy.

In addition to air quality, we studied the auto parts that people were most likely to touch, such as the steering wheel, dashboard, armrests and seats.

So, who won?

Well, it depends by what you mean by "won"! Here's a chart of the best and worst vehicles, by class.

So, the best vehicle?

The Chevy Cobalt is the least toxic vehicle.

The worst?

The Nissan Versa.

Why?

The Versa uses a lot of PVC (or polyvinyl chloride), brominated flame retardants and lead, compared to other vehicles. The car has PVC shift knob, door trim, armrests and center consoles, and exterior window seals.

The Versa is one of only 34 vehicles (out of 209) sampled that still uses a PVC instrument panel.

The seating in the vehicle includes a brominated flame retardant. It is likely that this is a chemical called "deca-brominated diphenyl ether," which is in the process of being banned in a number of states in the U.S., as well as Europe.

How can I find out what's in my car?

You can also compare vehicles on our web site. You can search by market segment, too. So, if you are interested in a small car or a SUV, you can find the healthiest choice.

These are fairly common chemicals. Why should we worry about them being in our cars?

The problem is that many of these chemicals are unregulated when it comes to using them in car interiors.

And they have all kinds of negative impacts on your health. Short-term problems include headaches and nausea.

Long-term problems include seeking advice from Car Talk...

I wouldn't be surprised. A detailed list of the chemicals we tested is available at our web site.

Seriously, what about long-term health concerns?

The average American spends over 1.5 hours in his car every day ... and over time, that's thousands of hours, sitting there breathing those fumes.

Long term, the result can be memory loss, cognitive, nervous and immune system problems, hormone and reproductive disorders and cancer. Did I mention memory loss?

Also, memory loss.

What's in "new-car smell"?

"New-car smell" is a concoction of tens or hundreds of chemicals that off-gas from different car parts.

One of the materials that plays a big role is vinyl, also known as PVC or polyvinyl chloride. Vinyl contains a chemical that off-gases and causes "fogging" on the inside of the windshield.

We found a lot of vinyl in vehicles with leather seats, which often have a very strong "new-car smell." While the front of the seats are usually real leather, in most cases the sides and back of the seats are made of vinyl. Consumers can't tell, because the vinyl industry has done a great job of making it look exactly like leather. Vinyl is one of the worst types of plastic. It's been strongly linked to fertility problems and cancer.

It's important for consumers to know that when they buy leather seats, they are actually buying a whole lot of vinyl.

We made a funny video that explains new-car smell, by the way. You can watch it right here.

Have you tested one- or two-year-old cars? Do you know how quickly these chemicals dissipate, and whether our cars become safer over time?

We haven't done that study, yet.

A study in Japan found that levels often decrease by ten-fold within a few months after manufacture. But, other chemicals, like heavy metals and flame-retardants, may be released much more slowly. For example, fabric and foam may degrade over time, releasing chemical-laden dust into the air.

In addition, older vehicles may contain chemicals that have been phased out or banned. For example, several flame-retardants were banned in recent years because of health concerns but, of course, these chemicals are still present in many older vehicles.

Let's say there's a car you want to buy, but it has unhealthy ratings on some of these chemicals. Is there anything you can do to protect yourself ... other than buying another car?

Sure. When you park your car, leave the windows open a crack to improve ventilation. Open your doors and thoroughly ventilate your car before getting in.

You can also park in the shade whenever possible, or use a solar reflector in the windshield, because heat and UV exposure accelerates the release of some chemicals.

We also recommend spending less time in your car by walking, biking or taking public transit whenever possible ... probably not good for business, for a show called, "Car Talk," I realize.

It's okay. Most of our listeners' cars don't run.

They've been taking your advice?

Exactly.

If you have a new car, does it make any sense to leave it in the sun and roll the windows down, to accelerate the "out-gassing" of chemicals?

That depends. For some chemicals, this might make sense. However, other chemicals, such as flame-retardants, are broken down by sunlight or high temperatures, sometimes into more toxic chemicals.

To complicate things further, some people are more or less sensitive to a given chemical. Ultimately, we hope that by making this information public it will nudge automakers into producing cars without these chemicals. Until then, we still recommend keeping the car cool and in the shade ... and find a way to spend less time inside your car.

How did you guys get started testing cars?

Our mission is to work towards a healthier environment. Finding solutions to auto pollution, in all of its forms, is one of our projects.

Automakers are as likely to disclose the details about which chemicals they use as my grandmother is to reveal her secret chili recipe. So, years ago, we set about doing this work ourselves.

When we started taking cars apart, we found toxics like lead in wheel weights, and mercury in some switches. Last year, we did a report on interior car dust; this year we wanted to know what parts of the car it was coming from.

How do you measure the amounts of those chemicals in the air?

With our X-ray gun, how else?

No kidding ... we literally shoot X-rays and the gun tells us what's in the materials in the vehicle. Your can check it out in this video. We test parts that people are most likely to come in contact with such as the steering wheel, dashboard, armrests, and seats.

We tested 15 parts in each of 209 vehicles ... over 3,000 samples by the time we were done. Finally, the information was peer-reviewed to make sure it made sense and was accurate.

How do you decide what chemicals to study?

We tackle the chemicals that are most toxic to human health. We look at chemicals that have been regulated in other parts of the world, such as the ones that can't be in products sold in Europe.

Is there any way for a consumer to test for these chemicals at home?

Technically, of course, it's possible. Unfortunately, a complete analysis of what you collected would cost several thousand dollars.

That's why think our web site is so useful.

And, for those folks shopping for a new car, we'll be sampling all vehicles next year and will report on any improvements in 2008 model year.

Are there federal laws that regulate exposure to these kinds of chemicals?

Generally speaking, no. And there are no regulations regarding air quality inside vehicles.

The chemical industry is not required under U.S. law to test most chemicals to prove that they are safe for humans or the environment. Shocking, eh? We think the industry should have to show safety before they use new chemicals.

When we do find out that a chemical is harmful, it's usually because scientists and public interest groups did the research and publicized their findings.

Are there alternatives that manufacturers can use?

Definitely! For each car component we tested there were manufacturers who did not use toxic chemicals. Every component can be made with safe material. We just need car manufacturers to make it a priority.

It's worth noting that we saw no correlation between vehicle price and levels of toxicity. Automakers can build healthy vehicles that are also affordable.

Have you contacted manufacturers with these results?

Yes, they're all aware of our findings, and surprisingly some are starting to pay attention.

Are they making any changes?

Mudslinging, panic ... all the usual responses. No, really, Ssome automakers seem to be making conscious efforts to clean up their vehicles, but there's still a long way to go. Ford and Volvo have begun to certify their vehicles to a voluntary standard that limits the amount of dangerous chemicals that can be used in the vehicle. This shows they understand that consumers are increasingly concerned about air quality, and are willing to do something about it.

We encourage folks to contact the manufacturers and let them know that they're interested in getting this information. We have a convenient list of all of the customer-service numbers on our web site. Ask them to certify to a standard. The more people who ask, the sooner it will happen.

What's the future hold for these concerns?

People like to breathe, even in their cars, so there is growing public awareness that the "new-car smell" isn't a good thing. If consumers make it clear to automakers that they want healthy cars that are safe for them and their families, the industry will be encouraged to clean up their act.

The best vehicles in our ratings are proof that the carmakers can do it without major costs. In the meantime, we all need to keep fighting for policies that regulate these sorts of chemicals in cars and other products.

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