Ovaries age faster than most organs, and chronological age only roughly describes this process. Scientists have found a way to look inside: in the fluid surrounding an egg, you can read both the chemical history of the body and the biological age of the ovary.
The study involved 76 women undergoing ovarian stimulation for IVF. Cells were isolated from the follicular fluid and the marks on their DNA were measured: it's like sand in a clockwork mechanism. The more chemical pollutants accumulated in the fluid, the faster the epigenetic clocks run, and the fewer eggs can be retrieved.
Among the chemicals, benzo[a]pyrene stood out in particular; it forms during frying food, smoking, and in exhaust fumes. It accelerated the aging of ovarian cells. The sand in the mechanism doesn't just slow down the movement, it damages the gears themselves: the genes that control follicle growth. This discovery will help doctors warn about fertility risks even before the clocks start to lag.
Follicular fluid, usually discarded after oocyte retrieval, turns out to be a valuable archive: it lets you read both the body's chemical history and the ovary's epigenetic age at the same time. The benzo[a]pyrene found in this fluid forms during incomplete combustion of organic matter and enters the body through fried food, tobacco smoke, and exhaust fumes.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.