Relationship between the length of service of female workers in non-ferrous metallurgy and their epidemiological fertility indicators

Introduction
This epidemiological study pursued the long-term exposure effects of noxious metal-compounds (Pb,Cd,Zn) on fertility of exposed female workers in non-ferrous metallurgy. An essential problem in the study was to find out the relations between the duration of working time of the exposed females and their epidemiological fertility indicators. 

Methods
The work-steps to be performed were the followings: 1.) Retrospective air monitoring (Pb,Cd,Zn) at all workplaces during a 10-yrs period. 2.) Study of health status of the exposed females. 3.) Data collection regarding the professional and non-professional factors with influence on fertility of studied females (fertility questionnaire). 4.) Evaluation of the fertility indicators: a/ Prevalence of spontaneous abortion (PSA), b/ Prevalence of premature (PP). 5.) Evaluation of relations between: duration of professional exposure time of the females and alterations in their health status fertility reflected in modifications of fertility indicators. 

Results
The workers under study (N=589), aged 40.45yrs+/-5.57 with a mean exposure time of 16.17yrs+/-1.83 belong to a much polluted area with Pb, Cd, Zn. Their biological monitoring confirms the level of exposure to the mentioned noxious metals. There are statistically significant differences (p<0.05) between the two groups: exposed and controls (N=537) regarding their fertility indicators. Pursuing the relation between the length of professional exposure time of the females and the PSA, there is a close correlation between them (correlation coefficient r~0.78; regression curve being linear, direct, positive). Regarding the relation between the duration of working time of the exposed females and the PP, there is also a close correlation between them(r~0.65; regression curve being linear, direct, positive). 

Discussion
This epidemiological study specifies only the intensity and the extension of the followed phenomenon in a collectivity of exposed female workers to the noxious metal-compounds without dose-effect relation evidence. The fertility indicators were modified in a significant exposure to metal-compounds, their degree of modification worsening with the increase of workers’ length of service.