CO2 also pollutes the environment for thousands of years.

"About 50% of a CO2 increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years." --IPCC AR4

http://www.realclimate.org/index.php/archives/2005/03/how-lo...

Plastics are a visible but small part of our environmental damage. Plastic straws doubly so.