Document DM2okVMRgX1Vwm2yXM6vXXp8a

TOXICOLOGY The effects of toxic agents on reproduction Post-partum toxicants, environmental agents to which a newborn may be exposed and suffer adverse effects, can be related to parental occupational exposure. Although the incidence of birth defects, spontaneous abortions and stillbirths among the human popula tion is quite high, with as many as 7% of all newborns born with birth defects in the United States annually', the cause of the vast majority of these defects is not known. It has been estimated that as many as 70% of all defects are of unknown encountered in the modern workplace environment. MODES OF DYSFUNCTION A sche matic presentation of some of the modes of reproductive dysfunction is given in Figure 1, which also shows which parent, male or female, may be at risk. Examples of toxic agents capable of inducing each mode of dysfunction are readily available. It adult male and female, and must also be classed as a gestational toxicant since it is a transplacental carcino gen. Adult male workers occupationally exposed to synthetic estrogen were found to develop gynecomastia and experience a decreased libido and infertility.5 Female workers with sim ilar exposures were observed to expe rience intermenstrual bleeding. DES has induced carcinoma of the vagina in young females exposed in utero, as well as experimentally in the mouse and hamster.* origin5. At the same time that hundreds of agents capable of causing reproductive failure or of inducing germinal and/or somatic mutation have been recognized, the actual mag nitude of their effect on human repro ductive health has not been quanti fied. should be apparent, however, that not all agents can be easily classified and some will fall into more than one category. For example, the synthetic hormone diethylstilbestero] (DES)5-1 is capable of inducing organ dysfunction in the PATERNAL FACTORS Manson has recently reviewed the influence of environmental agents on male repro ductive failure.7 Several modes of action are possible. There may be direct damage of male germ cells lead ing to mutation and/or infertility, It should be noted at the outset that reproductive failure in the form of stillbirth, spontaneous abortion or birth defects alone is not an adequate measure of the extent of reproductive hazard from toxic agents among human beings. Toxic agents can manifest them selves in a variety of ways, including adversely affecting the male or female reproductive cycle, possibly leading to infertility; causing the production of insufficient or defective sperm; preventing the successful im plantation of fertilized ova; or induc ing functional defects not readily observed at birth and, hence, not asso ciated with reproductive failure. It is the purpose of this paper to review briefly aspects of the toxicolo gy of human reproduction with a particular emphasis on the effects of those toxic agents which may be SOME POTENTIAL MODES OF REPRODUCTIVE DYSFUNCTION TYPE OF EFFECT ORGAN DYSFUNCTION insufficient/defective sperm an ovulation/defeetive ova implantation defects . spontaneous abortion GENETIC DEFECTS GESTATIONAL TOXICANTS pre-embryonic embryonic PARENT AT RISK a9 a Q 9 a9 Cf (Semen) 9 9 feta) POST-PARTUM TOXICANTS 9 fly Jeanne M. Stallman, PhD, Division of Occupational Health and Toxicology, American Health Foundation, New York. via lactation via inhalation CT 9 36 OCCUPATIONAL HEALTH AND SAFETY