The majority of grill mats will contain PTFE, which is the same compound that is used to give nonstick cooking pans and Teflon their smooth and slippery surfaces. This compound has been approved for use by the FDA, and is generally considered to be non-toxic.
However, when it comes to cookware, there are many questions surrounding whether it is safe to use. The manufacturing process involves the use of PFOA, which can present health risks when it is used in large quantities.
Manufacturers do claim that most of the PFOA is burned away during the manufacturing process, but trace amounts are likely to still be present. PFOA is something that has been labelled as a toxic substance by the EPA, and many companies are looking to alternatives.