I picked up a flyer from an Olfa dealer at a quilt show last year regarding "Caring for your OLFA Rotary Mat." This is what it says:
To clean your OLFA mat, use a generous amount of room temperature water and a few drops of mild detergent. Use a soft, mild bristle brush to create a lather and gently clean your mat. Rinse with room temperature water and wipe dry with a cotton towel. Please note that warm or hot water and direct sunlight may damage that mat.
Hope this helps.