[Olwyn Robertson]

Olwyn Robertson  asked the Naked Scientists:
   
Hi Chris,

Is it true that the carcinogen Benzene is given off by the material of which the dashboard, seats etc. of cars are made? I received a copy of an article claiming that, when we get into our car, especially if it is a hot car, we will breathe in copious amounts of Benzene, and should therefore open the windows and not put on the air conditioner until the interior has been aired. Your comments please?

Cheers,

Olwyn

What do you think?

[RD]

Chemicals found in the cars included the carcinogen benzene

http://en.wikipedia.org/wiki/New_car_smell

[Bored chemist]

I doubt that the amounts are "copious".
"Insignificant" is probably a better description.

[CliffordK]

As vinyls and plastics in your car degrade in the sun, they may release some volatiles...  which is why the plastics may eventually degrade and become brittle.  But for the most part it is a very slow process.

Vinyl doesn't contain any benzine.

Polystyrene is essentially a benzine polymer.

Your nose can pick up many solvents.  Pay attention, although you can habituate to them quickly.
If it smells bad...  air it out.
If it is ok...  you should be fine.

Also be careful about exhaust leaks and leaving the rear hatch open when driving.

[Prof. Utonium]

I've seen this bogus urban legend e-mail before and here was my response.

The report referenced in Snopes’ webpage is for the pollution FROM OUTSIDE the car, not what is generated inside. The report to read is, “Emissions from Plastics” (2003 Rapra review reports No 161, Vol 14, No 5). Yes, the plastics in automobiles can offgas many unsavory chemicals—and this report lists them ALL—but benzene is not singled out because it isn’t a major constituent. The 2001 report referenced in this Snopes article is also from Korea, a country with little or no emissions controls on their autos.

Any benzene in the automobile compartment is from outside the car due to the emissions from petroleum products (leaks, tank venting, exhausts, etc.) and it is worse in the wintertime, not the summer. This is because it has a tendency to condense/coalesce in the high-humidity passenger compartment when it comes in from outside.

The 2,000-4,000 mg/cu ft number is ridiculous.
2,000-4,000 mg = 2-4 g. At benzene’s density of 0.8765 g/cc, that is about 2.25-4.5 cc and at 25 drops per cc (pharmaceutical conversion), that is 56-112 drops of benzene per cubic foot. Maybe not the saturation point, but surely getting there. The air would feel astringent at those levels.

Additionally, there is NO SUCH THING as the “Acceptable Benzene level indoors is 50 mg per sq ft” (Does that mean that 50 mg per sq ft is okay outside?). The Threshold Limit Value (TLV) Time Weight Average (TWA), or the average amount someone may be exposed to day in and out, is 1 PPM. 50 mg/sq ft = 2 PPM. 2,000-4,000 mg/cu ft quoted in the e-mail is 79-158 PPM. 25 PPM for 8 hrs is the no effects level; 50-150 ppm for 5 hours produces headache, lassitude, and weakness.

The actual TOTAL quantity of Volatile Organic Compounds (VOCs) and Semi –VOCs (SVOCs) present in a NEW car are measured in Parts Per Billion (PPB), not in Parts Per Million (PPM), and not in Parts Per Thousand (PPT) as this email leads on; and its not even benzene.

Finally, if the plastics were decomposing at this rate, there wouldn’t be any left in the cabin. At 100 cu ft cabin volume (typical Honda Accord) and 2,000-4,000 mg/cu ft of all “benzene” (assuming nothing else decomposes), that equals roughly 4-8 cubic inches of plastic gone per event (e.g., per day). A car wouldn’t last the a summer at this rate.

With all the lawyers in the world looking to blame someone for their clients’ self-induced cancer, none of them have picked up on this yet? Right. It must really be untrue if a lawyer won’t even lie about it (like this email).

Regardless, we’ve all seen the haze the collects on our front windows from external dirt/oil, condensation, and, yes, plastics emissions. Opening your windows helps vent out any chemicals (as well as the heat) that might be there and makes it easier to cool down the car. Rule of thumb—if its hotter inside than out, open the windows for few hundred feet while you’re driving. You can also open the fresh air intake manually (not recirculate/Max AC).

From the 2003 Report, emissions are comprised of the following:
Volatile Organic Compounds (VOCs): alkanes, alkenes, aromatic hydrocarbons. carbonyl compounds, alcohols, esters, ethers, aldehydes, halogenated hydrocarbons, terpenes, nitrogen, halogens, and sulfur compounds.
Semi-Volatile Organic Compounds (SVOCs): high boiling point substances such as paraffins (lubricants), glycols, higher fatty acids and esters, phenols, phthalates, adipates, and dibenzoates (plasticizers), organic phosphorus compounds (flame-retardants), organic silicon compounds, halogenated hydrocarbons, amines (catalysts from PU materials), sulfates. Carbonates, nitrates (water based salts)