Benzophenone (BP)-type UV filters are widely used in a variety of personal care products
for the protection of skin and hair from UV irradiation. Despite the estrogenic potencies
of BP derivatives, few studies have examined the occurrence of these compounds in
human matrices. Furthermore, associations among exposure to these compounds and estrogen-dependent
diseases (such as endometriosis) have not been examined previously. In this study,
we determined the concentrations of five BP derivatives, 2-hydroxy-4-methoxybenzophenone
(2OH-4MeO-BP), 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2'-dihydroxy-4-methoxybenzophenone
(2,2'OH-4MeO-BP), 2,2',4,4'-tetrahydroxybenzophenone (2,2',4,4'OH-BP), and 4-hydroxybenzophenone
(4OH-BP), in urine collected from 625 women in Utah and California, using liquid chromatography
(LC)-tandem mass spectrometry (MS/MS). The association of urinary concentrations of
BP derivatives with an increase in the odds of a diagnosis of endometriosis was examined
in 600 women who underwent laparoscopy/laparotomy (n = 473: operative cohort) or pelvic
magnetic resonance imaging (n = 127: population cohort), during 2007-2009. 2OH-4MeO-BP,
2,4OH-BP, and 4OH-BP respectively were detected in 99.0%, 93.3%, and 83.8% of the
urine samples analyzed, whereas the detection rates for 2,2',4,4'OH-BP and 2,2'OH-4MeO-BP
were below 6.0%. Significant regional differences (higher concentrations in California)
and monthly variations (higher concentrations in July and August) were found for urinary
concentrations of 2OH-4MeO-BP and 2,4OH-BP. In addition, urinary concentrations of
2OH-4MeO-BP and 2,4OH-BP tended to be higher in more affluent, older, and leaner women.
Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for the
urinary concentrations of BP derivatives and the odds of an endometriosis diagnosis;
ORs increased across quartiles of 2OH-4MeO-BP and 2,4OH-BP concentrations, but a significant
trend was observed only between 2,4OH-BP and the odds of an endometriosis diagnosis
in the operative cohort (OR = 1.19; 95% CI = 1.01, 1.41). When women in the highest
quartile of 2,4OH-BP concentrations were compared with women in the first three quartiles,
the OR increased considerably (OR = 1.65; 95% CI = 1.07, 2.53). Given that 2,4OH-BP
possesses an estrogenic activity higher than that of 2OH-4MeO-BP, our results invite
the speculation that exposure to elevated 2,4OH-BP levels may be associated with endometriosis.