Love that new car smell?

That smell — so popular it's a trendy scent option at the carwash — is actually the offgassing of chemicals that can pose an assortment of health problems for automobile occupants, some of them quite serious. While researchers say that up to 275 chemicals can be found in the cabin in any given new car, they identify 50 as being significant in volume. The most notorious of the toxins found by air-quality researchers include phthalates, polyvinyl chloride (PVC), heavy metals, benzene, methylbenzene (toluene), bromine, and formaldehyde.

Unfortunately, there is no mandatory testing or regulation of chemicals inside vehicles sold in the United States. Thus, car buyers are mostly on their own, with little information as to the air-quality hazards of any particular vehicle they may be considering.

The toxic cocktail in automobiles comes from solvents, adhesives, lubricants, flame retardants, plastics, and other materials. Many of these chemicals are volatile organic compounds (VOCs), which may cause headaches, throat and eye irritation, allergies, confusion, and drowsiness. Great Britain's Daily Telegraph newspaper once equated the immediate effects of inhaling new-car cabin fumes to “sniffing glue.”

Regular exposure to significant levels of these toxins can pose other risks over the long term, including learning and memory impairment, birth defects, decreased fertility, and problems with the liver, thyroid, ovaries, kidneys, and blood. Benzene is a well-known human carcinogen and formaldehyde has been classified as a probable human carcinogen by the Environmental Protection Agency.

When car components are redesigned, it can further complicate the picture, according to Carolyn Cairns, an independent expert in product safety and risk assessment. "Many new materials are formulated with chemicals for which little or no testing has been done to establish toxicity. In many cases, analytical test methods have not been developed to detect them in vehicle air samples at levels that may be harmful."

When a car is freshly manufactured, many construction materials are still unstable and continue to offgas, particularly when the vehicle interior becomes hot. Fortunately, the offgassing lessens as a vehicle ages, dropping significantly within the first several months.

But once the offgassing period of a new vehicle ends, some of these chemicals may persist. At the end of a car's life cycle, the shredded plastic and other non-metallic parts that are discarded in our landfills or incinerated can pose health risks to the general environment. Landfill waste can leach out and contaminate soil and water, and when incinerated, some toxic compounds found in automobiles can be dispersed throughout the atmosphere.

Several research studies have been conducted on automotive interior air quality over the past 20 years. In response to complaints of “sick car syndrome” by new minivan owners in 2003, Japan's Osaka Institute of Public Health found that VOCs in the minivans were over 35 times Japan's health limit upon delivery. And while the institute found that levels had fallen under the limit four months later, they increased again in the hot summer months, taking three years to permanently remain below the limit.

But the most notable and recent study was conducted by the Ecology Center, an Ann Arbor, Michigan-based non-profit that tests consumer products for environmental safety. In 2012, its researchers tested more than 200 vehicles of model years 2011–2012 and produced a ranking of cars — from best to worst — in regard to air quality. The researchers observed that the potential toxicity of many of these compounds could pose serious long-term health risks.

It is worth noting that automakers have been reducing the amount of toxic chemicals in their cars in recent years. But while the Ecology Center found that car interiors were less toxic than in a similar study six years earlier, there were still some notable problems with the interiors of many of the models most recently tested. But as models change incrementally from year to year, and are often redesigned every three to five model years, there is no current interior air quality ranking of cars for consumers to use.

Jeff Gearheart, the research director at the Ecology Center, says that cars “function as chemical reactors, creating one of the most hazardous environments we spend time in.” Gearheart cited third-party research that Americans spend an average of 1.5 hours in cars each day, making cars a major source of indoor air pollution. “Since these chemicals are not regulated, consumers have no way of knowing the dangers they face,” says Gearheart.

Cairns adds that health risks are proportionate to exposure, and those who spend a considerable amount of time in a car would be at greater risk.

A possible silver lining in the Ecology Center study was that PVC, which was found in most every car manufactured in 2006, was present in just 73% of 2012 vehicles and that 60% of vehicles used flame retardants that did not produce bromine byproducts. Honda led the way in PVC reduction, removing it in all of its models. Two model years later, consumers can only hope automotive interiors continue to improve overall.

Manufacturers don't live in a vacuum and some of them are notably engaged in reducing the amount of toxins in their vehicles. A few automakers voluntarily subscribe to third-party chemical safety standards such as TUV Toxproof and OEKO-TEX Standard 100. Some countries, such as Australia, have strict laws regulating the air quality in automotive vehicles, and global car companies that comply with those standards may sell either the same or related vehicles in other countries, including the United States. U.S. automotive air-quality standards are considered particularly weak.

New car owners can protect themselves and their families from health hazards by regularly ventilating their vehicles, both while driving and not in use, and by keeping them cool as the temperatures rise. Parking in the shade or using sun-blocking apparatus on the windows go a long way toward keeping cars cool while parked, reducing offgassing. Also, owners should wipe down their interior car panels and instruments with a microfiber cloth regularly during the first year of ownership. Vacuuming and steam-cleaning the interiors, including carpets, upholstery and headliner can also significantly reduce the amount of contaminated dust and grime in the cabin.

But even if your car is no longer new, be aware that there are other ways it can put you at risk of sick car syndrome. Exhaust fumes can still find their way into car cabins and concentrations of carbon monoxide may be up to 10 times higher inside any given car than along the roadside. Driving or riding in a car remains a significant health hazard no matter the age of the vehicle.