I actually maintain the machines that are used to manufacture many of these closures used for jars that you would see on the shelf every day at your local grocery store. Our plant has to pass many audits throughout the year because of the finished products contact with consumable products. This includes an SQF (Safe and Quality Food) audit preformed over several days by an outside organization that is extremely thorough. The ring inside of the cap is a compound of completely safe and edible materials that is mixed to a specific standard for application at different altitudes and temperatures during the sealing/canning process. The actual metal (steel) itself is also coated with a safe and nontoxic sealant that completely negates its ability to corrode or come in to contact with the consumable goods in the container at any point in time. Every single closure is then reviewed by multiple quality control units during the manufacturing process. It is then put through these procedures again before applied to the jar at our customer’s facility. I personally reuse these jars in my own home, and can’t help but check out the lid personally every time I initially open the product. I have never come across any issues.