Do you use sunscreen?  If not, you aren't as crazy as those anti-science hippies who are trying to give their kids smallpox or starve poor nations, but you are not exactly up on the literature of the last 30 years either.

However, you may be no worse off, especially if you are a woman who might like to keep her uterus working. The uterus - that special place where a baby grows(1) when a woman gets pregnant - can sometimes have its tissue misplaced.  That's called endometriosis and it is when the tissue that normally lines the uterus is instead growing somewhere else. It can lead to heavy periods and even infertility.  While researchers know what it is, they don't really know why it happens.

But they think they may have one reason why. Endometriotic lesions have been correlated to estrogen levels so researchers recently investigated endometriosis instances related to endocrine-disrupting compounds, including the benzophenone-containing compounds in...sunscreens. Yes, sunscreen, the stuff we are all told to slather on lest we get skin cancer.

They used urine samples from 625 women.  They found that women with higher concentrations of the sunscreen agent 2,4-dihydroxybenzophenone, had a significantly greater rate of endometriosis than those with low concentrations.  There was no connection with other compounds.

Correlation in this case is really, really not causation so no one should throw out their sunscreen and sunbathe naked just yet. It may just be better not to spend a lot of time in the sun if you can avoid it.

Citation: Tatsuya Kunisue, Zhen Chen, Germaine Buck Louis, Rajeshwari Sundaram, Mary Hediger, Liping Sun, and Kurunthachalam Kannan, 'Urinary Concentrations of Benzophenone-type UV Filters in US Women and Their Association with Endometriosis', Environ. Sci. Technol., Just Accepted Manuscript DOI: 10.1021/es204415a

H/T Sunscreen Compound Linked To Endometriosis by Janet Pelley Chemical&Engineering News

NOTE:

(1) Sorry, fetus. I think only Republican women get pregnant with babies?