Often overshadowed by lead's well-deserved reputation for causing learning disabilities, seizures, and death is a fact we've known since Roman times: It impairs fertility. In the home, lead can be found in the old paint of houses built before 1978; the cartoon characters and other graphics on drinking glasses; vinyl products; certain folk remedies; metal trinkets; contaminated soil; and in the solder of old plumbing fixtures. It's a toxic heavy metal that can cause miscarriages and collect in the male reproductive system and create abnormal sperm. Some studies put lead as the culprit in up to one-fifth of unexplained cases of infertility.
Source: "Increased seminal plasma lead levels adversely affect the fertility potential of sperm in IVF," Human Reproduction