Check out the article here (http://content.usatoday.com/communities/greenhouse/post/2011/08/child-car-seats-contain-chemicals/1)
"It says these substances have been linked to allergies, birth defects, impaired learning, liver toxicity and cancer, and babies are particularly vulnerable because their bodies are still developing and they spend hours in car seats."
I am still totally in love with the Chicco KeyFit30. Aidan is almost 1 and still hasn't outgrown it. The 30"/30lb limit has made it last a bit longer for us. Remember how most car seats used to have limits of 22"/22lbs? Ick! Of course, the new rear-facing car seat law makes it a bit less exciting that Aidan still fits, but I still LOVE it! He's an inch short of the limit so we'll probably get him a new convertible carseat for his birthday.
Check out what's in your car seat here: http://www.healthystuff.org/departments/childrens-products/product.searchbrand.php