Do Not turn on A/C immediately after entering your car.
Please Open the windows after you enter your car and do not turn On the air-conditioning immediately. 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 has other effects, like it 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. It is recommended that before you turn on your car AC, you should open the windows and door to give time for the interior to air out before you enter. Benzene is a toxin that affects your kidney and liver, and is very difficult for your body to expel this toxic stuff.
Hoax or Fact:
Mixture of hoax and facts.
The message claims that you should not turn on your car AC as soon as you enter the car, warning about harmful Benzene emissions from your car interiors because of heat. It is a fact that benzene is a toxic chemical that can lead to variety of ill health effects, including anemia and cancer, specifically leukemia in humans. Benzene is emitted as a byproduct from the products that are manufactured using Benzene as a solvent (plastics, synthetic fibers and glues). In most cars, interiors are made from plastics, synthetic fabrics, and glues, some of which are manufactured using benzene. Also, few air fresheners contain certain quantity of Benzene. According to scientists, such interiors can emit trace amounts of benzene, especially under hot weather conditions. But the question is how much of Benezene is emitted from car interiors and can it cause any health hazards to humans.
A group of German scientists tested indoor air of motor vehicles for emissions of volatile organic compounds in heat - "parked sunshine" conditions. When the interiors were exposed to 14000 W of light, a total of 10.9 and 1.2 mg/m3 of volatile organic compounds were found in the indoor air of new and used motor vehicles respectively. The major compounds in the new vehicle were o,m,p-xylenes, C3 and C4-alkylbenzenes, dodecane, tridecane, and methylpyrrolidinone, while the used vehicle air contained acetone, methylpyrrolidinone, methylcyclohexane, acetaldehyde, o,m,p-xylenes, ethylhexanol, and toluene. More importantly, no toxicity was observed and these had no apparent health risks, including Benzene. Also note that this has got nothing to do with the AC that you are using in your car.
However, when in doubt, it is better to ventilate your car before you enter your car and turn on your AC just to feel good and get some fresh air.
Benzene - Facts and Effects
Toxicity of Parked Motor Vehicle Indoor Air