Forwarded email claims that car interiors contain toxic levels of cancer-causing benzene, which is used in the manufacture of dashboards, car seats, and air fresheners. It advises opening windows to expel trapped benzene before using the air conditioner or driving.
Description: Email rumor
Circulating since: May 2009
Status: Partly true / Overblown
Email example contributed by Glennis A., May 11, 2009:
Car A/C (Air Conditioning) MUST READ!!!
Please do NOT turn on A/C as soon as you enter the car.
Open the windows after you enter your car and turn ON the air-conditioning after a couple of minutes.
Here's why:
According to a research, the car dashboard, sofa, air freshener emit Benzene, a Cancer causing toxin (carcinogen - take time to observe the smell of heated plastic in your car).
In addition to causing cancer, Benzene poisons your bones, causes anemia and reduces white blood cells.
Prolonged exposure will cause Leukemia, increasing the risk of cancer. May also cause miscarriage.
Acceptable Benzene level indoors is 50 mg per sq. ft.
A car parked indoors with windows closed will contain 400-800 mg of Benzene. If parked outdoors under the sun at a temperature above 60 degrees F, the Benzene level goes up to 2000-4000 mg, 40 times the acceptable level...
People who get into the car, keeping windows closed will inevitably inhale, in quick succession excessive amounts of the toxin.
Benzene is a toxin that affects your kidney and liver. What's worse, it is extremely difficult for your body to expel this toxic stuff. So friends, please open the windows and door of your car - give time for interior to air out - dispel the deadly stuff - before you enter.
Analysis: While it isn't 100% false, this email is a font of misinformation nevertheless.
Starting with the basics, it's true that benzene is a toxic chemical known to produce a variety of ill health effects, including anemia and cancer (specifically leukemia) in humans.
The substance occurs both naturally (mainly as a component of crude oil) and as a byproduct of human activities, e.g. as a component of petroleum-based products (such as gasoline) and products manufactured using benzene as a solvent (such as plastics, synthetic fibers, dyes, glues, detergents, and drugs). It's also a constituent of tobacco smoke.
Low levels of benzene are typically present in outdoor air due to automobile exhaust and industrial emissions. Thanks to vapors emitted by household products such as glues, paints, and furniture wax, even higher levels of benzene can sometimes be found in indoor air, especially in new buildings.
Benzene in cars
Do automobile dashboards, door panels, seats, and other interior components emit benzene, as claimed in the email? Most likely. In most cars these items are made from plastics, synthetic fabrics, and glues, some of which are manufactured using benzene. According to scientists, such items may "off-gas" trace amounts of benzene, especially under hot weather conditions.
There's precious little information available on the ingredients of car air fresheners, though one European study found that some household air fresheners emit measurable amounts of benzene, so it's not inconceivable that some car air fresheners do, too.
The critical question is how much. Might all of these items, taken together, give off enough benzene to harm your health?
What the scientists say
Most of the published studies wherein benzene levels were measured inside passenger vehicles have been done under driving conditions, in traffic. So, while such studies have indeed found that in-vehicle benzene levels can significantly exceed those outside the vehicle, and could pose a human health hazard, this is mainly attributed to the presence of exhaust fumes.
By the way, the amounts of benzene actually detected by researchers, albeit significant, were much smaller than the amounts stated in the email. A 2006 study summarizing all the data collected to date reported in-vehicle benzene levels ranging from .013 mg to .56 mg per cubic meter — a far cry from the 400 mg to 4,000 mg per square foot (do they mean cubic foot?) reported above.
In the one study I was able to find that measured benzene levels inside parked cars with their engines turned off, the results were more benign. Toxicologists took samples of the air inside both a new and a used vehicle under simulated hot-sunlight conditions, measuring the levels of volatile organic compounds (VOCs) including C3- and C4-alkylbenzenes, and exposing human and animal cells to the samples to determine their toxicity. Despite the detectable presence of VOCs (a total of 10.9 mg per cubic meter in the new car and 1.2 mg per cubic meter in the old car), no toxic effects were observed. Apart from noting the slight possibility that allergy-prone individuals might find their condition exacerbated by exposure to such compounds, the study concluded there is "no apparent health hazard of parked motor vehicle indoor air."
When in doubt, ventilate
Despite this finding, some drivers may still be concerned about the presence of any benzene vapors inside their car, especially given the World Health Organization's stated position that there is "no safe level of exposure" to the carcinogen. They may also worry, per the email warning above, that turning on the vehicle's air conditioner might simply exacerbate their exposure to trapped toxins by recirculating contaminated air. There's no harm done, if that's the case — and much peace of mind to be gained — by opening the windows and ventilating the car first.
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Sources and further reading:
Benzene Facts
Centers for Disease Control and Prevention, 22 February 2006
Toxicity of Parked Motor Vehicle Indoor Air
Environmental Science & Technology, 2 March 2007
That New Car Smell? Not Toxic, Study Finds
LiveScience.com, 6 April 2007
Benzene and Its Methyl Derivatives: Derivation of Maximum Exposure Levels in Automobiles
Toxicology Letters, 5 January 2006
Concentrations of Volatile Organic Compounds in the Passenger Side and the Back Seat of Automobiles
Journal of Exposure Analysis and Environmental Epidemiology, May-June 1999
Benzene
World Health Organization
Last updated: 06/19/09
