Analysis of semen parameters and sex hormones under low-dose PAEs exposure in Chongqing college students and comparison with reference dose

Objective To analyze the associations of diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), di(2-ethyl)hexyl phthalate (DEHP) and butyl benzyl phthalate (BBzP) [which have reference doses (RfD) in the plasticizer, phthalates (PAEs)] with semen parameters and sex hormone levels in the young male adults, and evaluate the safety of RfD. Methods A total of 796 subjects were sampled from our previously established cohort of the male reproductive health in Chongqing college students (MARHCS) study. The contents of PAEs metabolites were detected in the urine samples of the subjects to estimate the daily intake of PAEs. Optimal scaling regression analysis was used to test their associations of the contents with semen parameters and sex hormone levels. Joinpoint regression model was applied to explore whether there were inflection points in the above associations, and the results were compared with RfD. Results Except for the metabolite of BBzP (MBzP) below the detection limit in the most individuals, the median daily intake of the other 3 PAEs was 0.1, 1.0 and 4.3 μg/(kg·d) for DEP, DnBP and DEHP, which were all significantly lower than the corresponding RfD [800, 100 and 20 μg/(kg·d)] and health guidance values [30, 10 and 50 μg/(kg·d)]. The metabolite of DEP (MEP) was correlated with the progressive motility, normal sperm morphology, and testosterone level (P < 0.01); DnBP metabolite (MnBP) was correlated with normal sperm morphology (P < 0.05). Among the 4 metabolites of DEHP, MEHHP and MECPP were related to estrogen level (P < 0.05), and MEOHP and MEHP to estrogen and progesterone levels (P < 0.01). But, inflection points were only observed in the correlations between DEHP and some parameters [threshold doses are 2.9~3.6 and 5.0~5.8 μg/(kg·d)]. Conclusion There are 12 kinds of associations of PAEs exposure with semen parameters and sex hormone levels in college students in Chongqing. PAEs, though below RfD, can still causes male reproductive damage.