Sorry, again, for the sensationalist title but it is true and you do need to know this. Especially if you have children. This is scary.
Have you ever read your car users manual? Most people don't. When I read this story, I actually went out to the car and read my manual for the first time. Sure enough, it says plainly, "In a hot car, do not turn on your air conditioner without opening the car windows fully to circulate fresh air into the car." It doesn't say why.
Here's why: Modern car interiors are put together with all sorts of plastics and polymers and sealed together with chemicals. When these items get heated up for an extended period of time, they emit gas. That gas contains a know cancer causing agent called Benzene. Benzene is notorious for causing bone marrow cancer and Leukemia. See Wikipedia about health effects of Benzene here.
Snopes.com reports about Benzene in cars:
Do not turn on A/C immediately as soon as you enter the car! Please open the windows after you enter your car and do not turn on the air-conditioning immediately.
According to research done, the car dashboard, sofa, air freshener emits Benzene, a cancer causing toxin (carcinogen - take note of the heated plastic smell in your car). In addition to causing cancer, 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 levels indoors is 50 mg per sq. ft.. A car parked with windows closed will contain 400 - 800 mg of Benzene. If parked outdoors, under the sun, at temperature above 60 degrees F (15.5 C), the Benzene level goes up to 2000 - 4000 mg, 40 times the acceptable level... And the people inside the car will inevitably inhale an excess amount of the toxins.
It is recommended that you open the windows and doors to give time for the interior to air out before you enter. Benzene is a toxin that affects your kidney and liver, and it is very difficult for your body to expel this toxic stuff.
Folks, especially those of you with small children, spread the word. Like I said, this is probably much more responsible for deaths and cancers than a hundred Fukushima's could ever be.
How many cars are there in the world?
Make sure that your car is one that is aired our before you or your loved ones enter. Spread the word.