I'm looking for a way to render a large percentage (30 to 50%) of Earth's human population infertile in about 10 years. Medicine and tech levels are approximately where they are now, maybe slightly more advanced.
- Sterility is permanent. No medical advances in the next 30 years will be able to undo the damage done.
- Absolutely non-lethal. Whatever makes people sterile can't kill them.
- People don't know that they have been rendered sterile till they attempt to have children.
- Common infertility tests will detect the infertility.
- Men and women are equally affected.
- The effect is global by the end of the 10 years.
- Wild life is unaffected by this event. They continue to reproduce, same as they always have.
This is a science-based question so a minimum of hand waving, please. Journal articles, equations or other authoritative sources are nice to have but not required in your answer.