This is what is on the OLFA web site in the frequently asked questions portion:
How do I reduce the strong plastic smell from my new rotary mat?
Due to production and distribution, a new OLFA rotary mat can emit an odorous smell that some people are sensitive too. To overcome this smell, we suggest that the mat be wiped down with a solution of equal parts lukewarm water and white vinegar, then let it set for five minutes. Afterwards, rinse off the mat and towel dry. Repeat as needed.