Occasionally you may notice a slight odor with a newly purchased mat. This odor will dissipate with time but here is a suggestion that can expedite the process:
Using your bathtub, put enough cool or tepid water in the tub to cover the mat and add ¼ cup of white vinegar for every gallon of water. Let it soak for at least 30 minutes to an hour in order to change the PH balance and remove the odor.
Rinse the mat with clear water, and then wipe the mat with a soft cloth to dry. Store it in a well-ventilated area to make sure it is completely dry. Remember that heat is an enemy of the mat so make sure it is on a flat surface and not stored in direct sunlight or exposed to any type of heat.
If you still notice the odor, you can repeat the process.