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Observations of Reproductive Functions among Workers in an Oil Refinery -- Louisiana

In 1981, male employees in the wastewater treatment plant of an oil refinery in Louisiana expressed concern about an apparent excessive rate of spontaneous abortions among their wives. By means of a questionnaire, consultants to the company studied the results of pregnancies among wives of the male workers (1). The reported rate (17%) of spontaneous abortions during the period the husbands were employed at the plant (from 1976, when the plant opened, to 1981) was over twice the rate (8%) for the period before the husbands began working at the plant (1934-1976) (p = 0.07).

Because of methodologic limitations of the study and continuing concern among the workers, union representatives of workers at the plant requested an investigation by the National Institute for Occupational Safety and Health (NIOSH). In 1982, NIOSH investigators conducted a cross-sectional evaluation of male reproductive functions among the workers. Observations of sperm morphology and tests for sperm concentration were made on the semen of 42 of the 62 male employees in the plant who had not had vasectomies or other known causes of infertility (2,3). For comparison, 74 persons working in other areas of the refinery or in administrative positions not at the same site were similarly examined.

Adjusting the data for differing periods of sexual abstinence, the mean sperm concentrations for the control group (79.9 million spermatozoa/cc of semen) did not differ significantly from that (68.2 million/cc) of the workers at the wastewater treatment plant (p = 0.16). The observed proportions of sperm with abnormal morphology for the test group (49%) and the comparison group (45%) were also similar.

Using a stepwise regression model, investigators also explored the relationship between sperm concentration and the number of hours worked in the plant during the previous 6 months. The duration of sexual abstinence before sample collection was most closely correlated with sperm concentration, while the number of hours worked correlated poorly with sperm concentration (p = 0.22). Sperm concentration was not significantly correlated with age, history of urologic abnormality, recent fever or illness, smoking, use of alcohol, marijuana, and other drugs, or frequent sauna or baths. Moreover, none of these factors was significantly associated with observed abnormalities in sperm morphology. Reported by Reproductive Health Activity, Industrywide Studies Br, Hazard Evaluations and Technical Assistance Br, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: Since azoospermia (absence of motile spermatozoa in the semen) and oligospermia (deficiency of spermatozoa in the semen) were noted in 1977 among chemical workers exposed to dibromochloropropane (DBCP), the effect of occupational exposures on semen has received increasing attention as an index of occupationally impaired reproductive function. The degree of reproductive risk that may be inferred from observed changes in sperm involves several links. First, recent evidence from human studies confirms earlier results from animal studies that certain exposures of males can increase the chance of spontaneous abortion in their mates, independent of female reproductive factors (4). Second, increases in abnormally shaped spermatozoa and decreases in the concentration of spermatozoa in the semen have been associated with infertility (5,6) and, to some extent, with a greater frequency of spontaneous fetal loss in the mates (7,8). Finally, research in animals and humans suggests that the concentration and morphology of spermatozoa may be sensitive indicators of impaired spermatogenesis and testicular function (9).

The findings presented here indicate a lack of effect of occupational exposures on the concentration and morphology of spermatozoa among workers at the time of study. Several factors must be considered in viewing these results in light of those of the earlier questionnaire survey. A comparison of rates of spontaneous abortion for 1976-1981 with those in 1934-1976 may involve a recall bias that could reduce the reliability of the findings. In addition, the questionnaire survey involved a small population with a necessarily small expectation of spontaneous abortions, which increases the possible influence of random fluctuations in a biologic event.

If, however, it is assumed that the results of the questionnaire accurately reflected the situation at that time, there are scientifically credible explanations for an observed increase in the rate of spontaneous abortions, such as: (1) genetic defects may have been present in the spermatozoa of some workers, leading to fertilizations by abnormal spermatozoa and subsequent fetal loss; (2) a significant toxic exposure may have been present in the past, but the effects were not detectable during the period of the NIOSH study; (3) spermatic abnormalities capable of producing fetal loss may have been present but not detectable by the methods used by NIOSH; and (4) embryotoxic substances on fomites, such as contaminated clothing or skin of the workers, may have been transmitted to the wives and led to fetal loss after normal fertilization.


  1. Morgan RW, Kheifets L, Obrinsky DL, Whorton MD, Foliart DE. Fetal loss and work in a waste water treatment plant. J Amer Public Health 1984;74:499-501.

  2. National Institute for Occupational Safety and Health. Health hazard evaluation report. Cincinnati, Ohio: National Institute for Occupational Safety and Health, l983. (HETA 82-387-1392).

  3. Rosenberg MJ, Wyrobek AJ, Ratcliffe J, et al. Sperm as an indicator of reproductive risks among petroleum refinery workers. Br J Ind Med 1985;42:123-7.

  4. Hemminki K, Kyyronen P, Niemi M-L, et al. Spontaneous abortions in an industrialized community in Finland. Am J Public Health 1983;73:32-7.

  5. Spira A, Mayauz MJ, Schwartz D, Jouannet P, Czyglik F, David G. Quelques aspects methodologiques d'une enquete retrospective comparant 484 hommes feconds et 2,768 hommes infeconds. Rev Epidem et Sante Publ 1980;28:13-20.

  6. Aitken RJ, Best FS, Richardson DW, et al. An analysis of sperm function in cases of unexplained infertility: conventional criteria, movement characteristics, and fertilizing capacity. Fertil Steril 1982;38:212-21.

  7. Czeizel E, Hancsok M, Viczian M. A habitualisan vetelo asszonyok ferjeinel vegzett ondovizsgalat jelentosege. Orv Hetil 1967;108:1591-5.

  8. Furuhjelm M, Jonson B, Lagergren CG. The quality of human semen in spontaneous abortion. Int J Fertil 1962;7:17-21.

  9. Wyrobek AJ, Gordon LA, Burkhart JG, et al. An evaluation of human sperm as indicators of chemically induced alterations of spermatogenic function: a report of the U.S. Environmental Protection Agency Gene-Tox Program. Mutat Res 1983;115:73-148.

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