Hello all having working in the Automotive industry for 15 years i can answer this one for you, I had the same email about 2 months ago. As some of you say if this were true then all the car manufacturers would already be out of business!!! forget the credit crunch it would have been LAW SUIT's against all manufacturers. Who ever carried out this research has potentially confused with Phenol alcoholic benzene which may come out of plastics, but is not carcinogenic.
All Plastics used in cars are tested in all conditions from extremely cold to exceptionally hot so you can rest assured there is nothing wrong with using plastics in cars, as for the AC use it you need it in this weather.