Lead (Pb), which is commonly found in batteries, metal products, paints, ceramics, and pipes, is one of the most prominent heavy metals. Environmental and occupational exposure to lead have been associated with increasing number of diagnosed fertility impairments. Lead interrupts the hypothalamic-pituitary axis and has been reported to alter hormone levels, alter the onset of puberty, and decrease overall fertility. Lead may alter sperm quality in men, and cause irregular menstruation, induce preterm delivery, and cause miscarriage, stillbirth, and spontaneous abortion in women. Chronic exposure to lead can also induce functional disorder (decrease of testosterone synthesis) or morphological disorder.
Mercury (Hg) is commonly found in thermometers, batteries, and industrial emissions. Mercury concentrations increase in the food chain, resulting in bioaccumulation that can negatively impact reproduction in humans who consume food, usually tainted seafood. Ultimately, mercury can disrupt spermatogenesis and disrupt fetal development.
Boron (B) is another heavy metal that is used in the manufacturing of glass, cement, soap, carpet, and leather; its effects on the hypothalamic-pituitary axis are comparable to lead.
Chronic exposure to heavy metals such as As (arsenic) may also affect sperm quality. Trace amounts of As have been observed in semen which suggests that it may inhibit the function of enzymes present in the acrosome and the membrane which covers the head of the sperm.
While there is not much research on cadmium (Cd), it has been shown experimentally to cause testicular necrosis in mice, as well as marked changes in libido and infertility. Heavy metal toxicity has been associated with male infertility, reproductive disorder, reduced spermatogenesis, and so forth. Cd in combination with other heavy metals such as Cr (chromium), As (arsenic), and Pb (lead) may account for decreased male fertility rate in the developed countries observed by reduced sperm counts and testis function.