Recent in vitro studies have shown that some chemical UV filters mimic the effect of progesterone in the activation of the CatSper Ca2+ channel in human spermatozoa. However, so far, the extent of exposure of human spermatozoa to chemical UV filters via the presence of these chemicals in seminal fluid has been unknown. Here, we present levels of UV filters measured in human seminal fluid and comparisons to levels measured in concurrently collected urine and serum samples. In total nine UV filters were analysed by TurboFlow-LC-MS/MS in paired urine, serum, and seminal fluid samples from 300 young Danish men from the general population; each man collected one of each sample type within 1 h. The samples were collected during February-December 2013 and only six of the men reported having used sunscreen during the 48 h preceding the sample collection. Four of the examined UV filters could be detected in seminal fluid samples at levels above LOD in more than 10% of the samples. Benzophenone (BP), benzophenone-1 (BP-1), and benzophenone-3 (BP-3) were most frequently detected in, respectively, 18%, 19%, and 27% of the seminal fluid samples albeit at levels one to two orders of magnitude lower than the levels observed in urine. 4-methyl-benzophenone (4-MBP) was detectable in 11% of the seminal fluid samples while in <5% of the urine samples. Overall 45% of the men had at least one of the UV filters present in their seminal fluid at detectable levels. For BP-1 and BP-3 individual levels in urine and seminal fluid were significantly correlated, while this was not evident for BP nor 4-MBP. In conclusion, chemical UV filters are present in men's seminal fluid; some of which can activate the human sperm-specific CatSper Ca2+ channel and thereby potentially interfere with the fertilisation process.
Keywords: Benzophenone; CatSper Ca2+ channel; Endocrine disruptor; Human biomonitoring; Seminal fluid; UV filter.