Hi,
There are three main concerns with commercial tampons: asbestos, rayon, and dioxins. Asbestos can cause excessive bleeding, rayon can lead to TSS because of its super absorbancy, and dioxins are used in bleaching. They have been linked to cancer and reproductive problems.
Even so...I still use Playtex myself. Not quite ready to make that switch yet. If it makes you feel better, I read that tampons that expand lengthwise (tampax) are irritating to the cervix and can cause irregular pap tests and susceptability to HPV. So playtex aren't the worst ones...