Same problem with my large Olfa mat. I too am overly sensitive to smells, odors, etc. I never smelled it until I brought it home. Everyone that came within 10 ft of the mat could smell it. I left it outside in the garage for a good week. Still could smell it a little after bringing it in. Been about 6 months, and I can no longer smell it even with the windows closed. I thought the odor would go into the fabric when cutting, but it didn't. The odor on my mat 'just went away'. I think the smell (cigarette smoke-which was denied by seller) from fabric received on Ebay once was far worse than the mat smell. I should add mine is the self-healing mat.
Olfa.com FAQ says:
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.