Combining reproductive studies of men exposed to 2-ethoxyethanol to increase statistical power.
Schrader-SM; Turner-TW; Ratcliffe-JM; Welch-LS; Simon-SD
Occup Hyg 1996 Jan; 2(1-6):411-415
A statistical analysis was performed on data obtained from two earlier studies in which workers had been occupationally exposed to 2-ethoxyethanol (110805) (2EE). In the first study, 37 men were evaluated who used 2EE in a metal castings company. The second study involved 40 men exposed to 2EE in a spray painting operation. The breathing zone exposure in the first study was 6.6 parts per million (ppm) (24.4mg/m3) and in the second was 2.7ppm (9.9mg/m3). In each study the men also had substantial skin exposure to 2EE. Semen analysis was conducted on each man after a requested 2 day abstinence time. Sperm concentration and semen volume indicated a significant effect of exposure to 2EE when the studies were combined, while neither of the studies individually indicated significant differences. For the parameter of sperm/ejaculate, percent normal sperm forms, curvilinear velocity of the sperm cells, and percent viability sperm by stain exclusion, the combined p-value lies between the p-values of the individual studies. The percent motility and percent viable by hypoosmotic swelling p-values decreased when the studies were combined. The authors suggest that these findings support the need to publish the data from all studies whether or not a highly significant difference is observed. Such publications would allow for combining data from complementary studies. Using a mixed model of analysis of variance with a random effect for study location, the men in these two studies exposed to 2EE had significantly lower sperm concentrations and semen volumes than men in the control populations.
NIOSH-Author; Reproductive-hazards; Skin-exposure; Reproductive-system-disorders; Risk-factors; Epidemiology; Fertility; Occupational-exposure; Metal-workers; Painters; Spermatogenesis