High exposure to phthalates, which are ubiquitous contaminants, has been shown in animal studies to produce detrimental effects on male reproductive functions. A recent study in humans reported dose–response relations between low phthalate levels in urine and human semen parameters, which raises the question whether humans are more sensitive to phthalate exposure than animals.
Urine, serum, and semen samples were collected from 234 young Swedish men at the time of their medical conscript examination. Semen volume, sperm concentration, and motility were measured, together with sperm chromatin integrity (sperm chromatin structure assay) and biochemical markers of epididymal and prostatic function. We analyzed reproductive hormones in serum, and mono ethyl phthalate (MEP), mono ethylhexyl phthaltale (MEHP), mono benzyl phthalate (MBzP), mono butyl phthalate (MBP), and phthalic acid in urine.
For MBP, MBzP, and MEHP, no clear pattern of associations were observed with any of the reproductive biomarkers. Subjects within the highest quartile for MEP had fewer motile sperm (mean difference = 8.8%; 95% confidence interval = 0.8–17), more immotile sperms (8.9%; 0.3–18), and lower luteinizing hormone values (0.7 IU/L; 0.1–1.2), but there was no suggestion of harmful effects for most other endpoints. Phthalic acid actually was associated with improved function, as measured by several markers.
The observed weak associations between 1 phthalate biomarker and impairment of a few aspects of reproductive function biomarkers were not consistent with results from a recent U.S. study. It is not yet possible to conclude whether phthalate exposure may reflect a hazard for human male reproduction.
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From the *Department of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University Hospital, Lund; and Fertility Center, Malmö University Hospital, Malmö, Sweden.
Submitted 17 December 2003; final version accepted 7 March 2005.
†Supported by the Swedish Research Council, AFA foundation, the Swedish Governmental Funding for Clinical Research, Crafoordska Fund, Ove Tulefjords Fund, Foundation for Urological Research, and the Medical Faculty of Lund University.
Supplemental material for this article is available with the online version of the journal at www.epidem.com
Correspondence: Bo Jönsson, Department of Occupational and Environmental Medicine, University Hospital, SE-221 85 Lund, Sweden. E-mail: Bo.Jonsson@ymed.lu.se.