If chemicals in products are important to you and your children, then you might be interested in this site: Healthy Car– chemicals in car’s and car seats.
I wouldn’t ever think of chemicals in car seats as being that important, but it’s interesting nonetheless!
I’m a little surprised to find the Britax Marathon as one of the most concerned seats. It won’t stop me from getting one though- these seats are highly recommend for safety which in my option is the most important!
As a reminder and as noted in a previous post, and which you may find much more interesting and important- is Healthy Toys, which shows chemicals found in toys.
Samantha Mellen Fitness LLC 
that is really interesting, thanks for sharing!!