Surprisingly a question we get fairly often: 

Is it safe to use tea bags?

Yes, it is safe to use tea bags.

It may not be safe to consume tea from dubious sources i.e. if the seller is an unknown, you could be buying expired or contaminated tea that should be disposed of but is being sold unscrupulously. This is certainly more common in teabags as it would be difficult to know if the tea inside the teabags is bad (unless there is a distinct, foul smell, etc.).

If you want to be sure, purchase tea from brands and preferably of the loose-leaf variety. Strainers are easily available and you will get more value and better taste from loose leaf teas.