This is a copy from a chain e-mail I received: 

Check the labels of the sanitary pads or tampons that
  you are going to buy the next time, and
  see whether you spot any of the familiar signs stated
  in this email...... no wonder so many women in the
  world suffer from cervical cancer and wombtumors......
  Have you heard that tampon makers include asbestos in
  tampons? Why would they do this? Because asbestos
  makes you bleed more . . . if you bleed more, you're
  going to need to use more. Why isn't this against the
  law since asbestos is so dangerous? Because the powers
  that be, in all their wisdom(not), did not consider
  tampons as being ingested, and therefore wasn't
  illegal or considered dangerous. This month's Essence
  magazine has a small article about this and they
  mention two manufacturers of a cotton tampon
  alternative. The companies are Organic Essentials @
  (800) 765-6491 and Terra Femme @ (800)755-0212.
  A woman getting her Ph.D. at University of Colorado @
  Boulder sent the following: "I am writing this because
  women are not being informed about the dangers of
  something most of us use - tampons. I am taking a
  class this month and I have been learning a lot about
  biology and woman, including much about feminine
  hygiene. Recently we have learned that tampons are
  actually dangerous (for other reasons than TSS). I'll
  tell you this, after learning about this in our class,
  most of the females wound up feeling angry and upset
  with the tampon industry, and I for one, am going to
  do something about it. To start, I want to inform
  everyone I can, and email is the fastest way that I
  know how. Here is the scoop: Tampons contain two
  things that are potentially harmful: Rayon (for
  absorbency), and dioxin (a chemical used in bleaching
  the products). The tampon industry is convinced that
  we, as women, need bleached white products - in order
  to view the product as pure and clean. The problem
  here is that the dioxin produced in this bleaching
  process can lead to very harmful problems for a woman.
  Dioxin is potentially carcinogenic
  (cancer-associated) and is toxic to the immune and
  reproductive systems. It has also been linked to
  endometriosis and lower sperm counts for men- for
  both, it breaks down the immune system.
  Last September the Environmental Protection Agency
  (EPA) reported that there really is no set
  "acceptable" level of exposure to dioxin given that it
  is cumulative and slow to disintegrate. The real
  danger comes from repeated contact (Karen Houppert
  "Pulling the Plug on the Tampon Industry"). I'd say
  using about 4-5 tampons a day, five days a month, for
  38 menstruating years is "repeated contact", wouldn't
  you? Rayon contributes to the danger of tampons and
  dioxin because it is a highly absorbent substance.
  Therefore, when fibers from the tampons are left
  behind in the vagina (as it usually occurs), it
  creates a breeding ground for the dioxin. It also
  stays in a lot longer than it would with just cotton
  tampons. This is also the reason why TSS (toxic shocksyndrome)
  occurs.
  WHAT ARE THE ALTERNATIVES? Using feminine hygiene
  products that aren't bleached and that are all cotton.
  Other feminine hygiene products (pads/napkins)
  contain dioxin as well, but they are not nearly as
  dangerous since they are not in direct contact withthe vagina.
  The pads/napkins need to stop being bleached, but
  obviously tampons are the most dangerous. So, what can
  you do if you can't give up using tampons? Use
  tampons, that are made from 100% cotton, and that are
  UNBLEACHED. Unfortunately, there are very, very few
  companies that make these safe tampons. They are
  usually only found in health food stores. Countries
  all over the world (Sweden,German, British Colombia,
  etc.) have demanded a switch to this safer tampon,
  while the U.S. has decided to keep us in the dark
  about it. In 1989, activists in England mounted a
  campaign against chlorine bleaching. Six weeks and
  50,000 letters later, the makers of sanitary products
  switched to oxygen bleaching (one of the green methods
  available). (MS magazine, May/June 1995).WHAT TO DO NOW:
  Tell people. Everyone. Inform them. We are being
  manipulated by this industry and the government, let's
  do something about it! Please write to the companies:
  Tampax (Tambrands), Playtex, O.B., Kotex. Call the 800
  numbers listed on the boxes. Let them know that we
  demand a safe product - ALL COTTON UNBLEACHED TAMPONS.