Exposure to diesel exhaust affects the male reproductive system of mice

Several recent reports have suggested that sperm count and quality in norma l men are declining. Various environmental chemical compounds may affect th e male reproductive system. We propose here that diesel exhaust is an envir onmental pollutant with the potential to influence male reproductive functi on. Ultrastructural changes were observed in Leydig cells of mice exposed t o diesel exhaust (0.3 mg diesel exhaust particles (DEP)/m(3) through the ai rway, 12 h daily, up to 6 months) and reduction in LH receptor mRNA express ion in Leydig cells was observed at a concentration of 1 mg DEP/m(3). Daily sperm production per gram of testis dose-dependently decreased with exposu re to DE for 6 months; 29%, 36%, and 53% reductions were observed at 0.3, 1 .0, and 3.0 mg DEP/m(3), respectively. A no-observed-adverse-effect level ( NOAEL) was observed with approximately 30 mu g DEP/m(3), which is lower tha n the WHO-recommended limit.