Male infertility chemicals

Barchielli A, Buiatti E, Franchini M, et al. 1982. Male infertility and occupational exposure to chemical agents A review. Med Lav 73 483-495. 

Xenobiotic chemicals are thought to contribute to all these causes of infertility, though the effects of chemical mixtures on infertility have only recently begun to be explored. This chapter examines the effects of chemical mixtures on female and male infertility from the perspectives of the impacts of exposures in adults as well as fetuses. 

There has been a significant increase in male infertility over the past three-quarters of the century. This time frame corresponds to one where dramatic increases in the use of pesticides and other synthetic chemicals have occurred. Many different chemicals have been associated with male infertility including pesticides, heavy metals, dioxins, PCBs, phthalates, and others. 

As discussed earlier, male infertility has been associated with exposures to xenobiotic chemicals. Though affects have been reported for single chemicals, most are based on laboratory testing on animals, since most environmental exposures to humans come from mixtures. Some data, however, has been collected from infertility induced by industrial and environmental exposures. Table 23.3 contains a partial list of chemicals associated with male infertility. I48,58-66 These chemicals include pesticides, heavy metals, and industrial chemicals. 

Exposures to the chemicals listed in Table 23.3 are rarely to single chemicals. Regretfully, few studies have been carried out on the effects of mixture exposure and male infertility. Those that have addressed this subject have shown that unanticipated effects are indeed encountered. The following illustrate this point. 

Table 23.3 Endocrine Disrupting Chemicals Associated with Male Infertility Pesticides...

Newer tools for the detection of Y chromosome deletions have further strengthened (he hypothesis that the decline in male reproductive health and fertility may he related to the presence of these toxic chemical compounds in the environjnent. The development of intracytoplasmic sperm injection (ICST), a technique introduced in the early 1990s, i.s beyond doubt the most important recent breakthrough in the treatment of male infertility. This was made... 

Exposure to xenobiotics raises the risk of male infertility, breast cancer in females, feminization of male animals and the evolution of antibiotic resistant strains of bacteria. Of particular concern are endocrine disruptors such as polychlorinated biphenyls (PCBs), which are chemicals that at certain doses can interfere with the endocrine (or hormone) system in mammals. These disruptions can cause cancerous tumours, birth defects and other developmental disorders. 

A case-control study of the effects of occupational exposures on male infertility found that a mixture of styrene = 2.95) and acetone = —0.24) affects the male genital system and leads to impotence, infertility, and increased SABs in their wives [77]. Similar effects were reported following workplace exposures to pesticides, heavy metals, and other chemicals. No mechanism(s) for the actions of these chemicals were reported. 

Chemicals can also directly affect male reproductive organs or sperm. Decreased sperm count, decreased sperm motility, or abnormalities can result in male sterility or reduced fertility. For example, occupational exposure to lead can result in infertility due to sperm abnormalities. Male sterility can also result from exposure to the fungicide dibromochloropropane (DBCP). Drugs or chemicals, such as... 

Female reproduction may be recognized to be complex because it has been studied in greater detail and many more aspects of the female reproductive system are defined than for the male. Certainly the female reproductive system is overtly more dynamic and, perhaps because of this dynamicism, more susceptible to physical, chemical, and emotional stressors. The discrete series of events of the ovarian cycle which requires precise coordination between the central nervous system, hypothalamus, and pituitary in order for gametogenesis and ovulation to take place provides the opportunity for environmental changes to adversely influence normal processes. If these events are delayed or altered appreciably, some form of short-term infertility will most likely result. When this is compared to the male, the relatively monotonous production of hormone and gametes is not as likely to be overtly influenced by short-term events. 

Toxic infertility as used here refers to adverse effects on the reproductive systems of human males and females that result from exposure to xenobiotic single chemicals and chemical mixtures. This infertility may be because of direct toxic effects on the male or female reproductive organs and endocrine systems, or on the developing fetus such that the fetus cannot be either conceived or carried to term after conception. Developmental toxicity, the onset of adverse effects on the developing fetus or child after birth are discussed in Chapter 24. 

Human infertility can result from the action of xenobiotic chemicals on the female reproductive system, the male reproductive system, attack on the fetus, and the induction of effects in utero that are manifest during adulthood, giving rise to a programmed infertility. Spontaneous abortion can ensue when pregnant women are exposed to toxic chemicals such as those in disinfection byproducts produced by the chlorination of drinking water. 

---