How toxic is your car?

A new US study shows which cars are most - and least - toxic to drivers. Photo / Thinkstock

An American company has released a report on the toxic chemicals that your typical vehicle releases, with the Honda Civic topping the list as the "healthiest" car while Mitsubishi's's Outlander is at the bottom.

It is the fourth consumer guide to toxic chemicals in cars from the Ecology Centre, which provides information on sustainable living.

The results are on the centre's website, HealthyStuff.org, with more than 200 of the most popular 2011- and 2012-model vehicles tested, using a portable x-ray fluorescence analyser, for chemicals that release gas from parts such as the steering wheel, dashboard, armrests and seats.

These chemicals contribute to "new car smell" and, according to Ecology Centre, cause a variety of acute and long-term health concerns.

In the US, toxic chemical exposure inside vehicles can be a major source of indoor air pollution as your average American is in their car 90 minutes a day.

"Research shows that vehicle interiors contain a unique cocktail of hundreds of toxic chemicals that [release] gas in small, confined spaces," says Jeff Gearhart, Research Director at the Ecology Centre.

"Since these chemicals are not regulated, consumers have no way of knowing the dangers they face. Our testing is intended to expose those dangers and encourage manufacturers to use safer alternatives."

Chemicals of primary concern included: bromine (associated with brominated flame retardants); chlorine (indicating the presence of polyvinyl chloride, or PVC); lead; and heavy metals.

Such chemicals have been linked to a wide range of health problems such as allergies, birth defects, impaired learning, liver toxicity, and cancer.

Cars are particularly harsh environments for plastics, as extreme air temperatures of 89C and dash temperatures of up to 120C can increase the concentration of volatile organic compounds and break other chemicals down into more toxic substances.

The Civic achieves its ranking by being free of bromine-based flame retardants in all interior components, utilising PVC-free interior fabrics and interior trim, and having low levels of heavy metals and other metal allergens.

The Mitsubishi Outlander contains bromine and antimony-based flame retardants in the seating and centre console, chromium treated leather on several components, and lead in seating materials.

Vehicles assembled in Asia (the majority of the cars sold in New Zealand are built in Asia-Pacific), utilised significantly less PVC in vehicle components.

But cars assembled in Europe used the most PVC, more than double the amount in other parts of the world.