In 1992 Carlsen et al. reported a significant global decline in sperm density between 1938 and 1990 [Evidence for Decreasing Quality of Semen during Last 50 Years. Br Med J 305:609-613 (1992)]. We subsequently published a reanalysis of the studies included by Carlsen et al. [Swan et al. Have Sperm Densities Declined? A Reanalysis of Global Trend Data. Environ Health Perspect 105:1228-1232 (1997)]. In that analysis we found significant declines in sperm density in the United States and Europe/Australia after controlling for abstinence time, age, percent of men with proven fertility, and specimen collection method. The declines in sperm density in the United States (approximately 1.5%/year) and Europe/Australia (approximately 3%/year) were somewhat greater than the average decline reported by Carlsen et al. (approximately 1%/year). However, we found no decline in sperm density in non-Western countries, for which data were very limited. In the current study, we used similar methods to analyze an expanded set of studies. We added 47 English language studies published in 1934-1996 to those we had analyzed previously. The average decline in sperm count was virtually unchanged from that reported previously by Carlsen et al. (slope = -0.94 vs. -0.93). The slopes in the three geographic groupings were also similar to those we reported earlier. In North America, the slope was somewhat less than the slope we had found for the United States (slope = -0.80; 95% confidence interval (CI), -1.37--0.24). Similarly, the decline in Europe (slope = -2.35; CI, -3.66--1.05) was somewhat less than reported previously. As before, studies from other countries showed no trend (slope = -0.21; CI, -2.30-1.88). These results are consistent with those of Carlsen et al. and our previous results, suggesting that the reported trends are not dependent on the particular studies included by Carlsen et al. and that the observed trends previously reported for 1938-1990 are also seen in data from 1934-1996.

/pdf/the-question-of-declining-sperm-density-revisited-an-1mxyi8ogs6.pdf

The question of declining sperm density revisited: an analysis of 101 studies published 1934-1996.

This reference book covers all aspects of male reproductive biology and applied clinical diagnosis and therapy and includes a lab manual. Chapters are authored by physicians in the fields of urology, gynecology and endocrinology providing discussions on developments in male infertility.

Infertility in the Male

A study was made of possible reasons for workers losing time from work at the Maritime Administration Reserve Fleets at Benicia, California and Fort Eustis, Virginia. At these worksites, activities associated with the mooring, preservation and maintenance of ships in the National Defense Reserve were undertaken. Most of the work involved manual materials handling tasks associated with the movement of ships in and out of the fleet, such as the handling of anchors, anchor inspecting and maintaining the engine room, cargo holds, and deck machinery with time spent in welding, metal working, painting, and other maintenance activities. The most frequent injuries occurring to workers at these sites included back muscle strains and sprains, groin pulls and hernias. Less prevalent injuries included eye injuries due to foreign objects, nail punctures to the soles of the feet, and muscle strains and sprains. There was also potential exposure to asbestos observed at both sites. A potential health hazard existed from pulling steel cable and nylon rope, lifting and carrying marine batteries, nail punctures, slips and falls, vibrating handtools, and foreign bodies in the eyes. Measures for lowering the risks of musculoskeletal and traumatic injuries and for reducing possible asbestos exposures are recommended.

Health hazard evaluation report

Occupational exposure to pesticides and consequences on male semen and fertility: A review

Existing data concerning the effects of x-irradiation on spermatogenesis in man were analyzed and the results were compared to published data on the mouse. Testicular x-irradiation produced a transient, but substantial, suppression of sperm counts in man, with an ED50 near 11 rad. The length of time to recovery was proportional to the irradiation dose. The ED50 for suppression of type A spermatogonia following radiation exposure in man was similar (9.7 rad), although the response curves for spermatogonia and sperm count were matogonia in the mouse was parallel to that found in man, but with an ED 50 of 30.0 rad. These results suggest that, compared to the mouse, spermatogenesis in man is approximately 3.1 times more sensitive to ionizing irradiation.

The effect of testicular x-irradiation on spermatogenesis in man. A comparison with the mouse.

Male pesticide applicators who worked with the nematocide dibromochloropropane (DBCP) were examined to determine the possible testicular toxicity from this exposure. Infertility and azoospermia which were first noted among factory workers exposed to DBCP were not observed among the applicators. Sperm count depression, however, was associated with the duration of exposure in the current year but not with exposure in past years. The extent of exposure to DBCP in the current year was also associated with an elevation of serum follicle stimulating hormone (FSH) but not of luteinizing hormone (LH). Sperm count depression was limited to applicators involved in irrigation setup work and in the calibration of equipment. These results suggest that the testicular toxicity of DBCP for men may occur in a shorter period than was previously reported, that the effect may be reversible in men with mild sperm count depression, and that public health measures might be directed at controlling specific application techniques.

R. I. Glass

Papers

Sperm count depression in pesticide applicators exposed to dibromochloropropane.