OBJECTIVE : The purpose of this paper was to analyze the relationship between the selected chemical air pollutants found in the Lublin Province and the semen parameters of men seeking fertility treatment for the first time. METHODS : The study involved an analysis of semen sample test results obtained from male patients first reporting for fertility treatment in reproductive health centers in the Lublin Province, Poland. The data set comprises semen parameters of 13 148 men, and the number of samples in the reference period was 255-769 annually. Data on air pollution were obtained from the website of the Polish General Environmental Inspectorate and included selected chemical air pollutant levels, i.e., NO2, SO2, O3, and PM10. RESULTS : The mean PM10 levels in the air increased, on average, by 0.65 μg/m3 annually in 2000-2015 (p = 0.029); the mean levels of O3, NO2, SO2 did not change significantly in the analyzed period. There were increasing trends in the mean sperm density and total sperm count of the subjects in 1992-2015 (p < 0.001). The mean percentage of sperm with normal morphology significantly decreased in the subsequent analysis periods: 1992-1998 (p = 0.001); 1999-2009 (p < 0.001); 2010-2015 (p = 0.001). A significant negative correlation was found between the ozone levels in the air in the Lublin Province and the percentage of sperm with normal morphology (r = -0.8311, p = 0.040). CONCLUSIONS : Exposure to ozone in the air contributes to decreased percentages of sperm with normal sperm morphology. Over the years, there was an increasing trend in sperm density in the men first reporting for fertility treatment, and a decreasing trend in the percentage of sperm with normal morphology. Int J Occup Med Environ Health. 2019;32(3):387-99.