Much like the Malayan tiger, the landline telephone, and Arcade Fire’s credibility, our sperm is in serious danger of going extinct. In a new meta-analysis released this week in the journal Human Reproduction Update, Israeli researchers discovered that sperm counts in men in America, Europe, Australia, and New Zealand have precipitously plummeted in recent years and will likely continue to drop.

The scariest part? Scientists don’t really know why.

Researchers at Hadassah-Hebrew University in Jerusalem analyzed 185 previous studies dating back to 1973 in hopes of seeing how men’s sperm counts changed over time. They found a disturbing trend: For men in Western nations, sperm counts fell 1.4 percent every year between 1973 and 2011.

The scientists didn’t see a similar drop among guys in Asia, Africa, or South America, which hints that some environmental factors may play a role. Though you can speculate that men in more advanced nations may be exposed to more sperm-killing chemicals—such as bisphenol-A (BPA), which research has linked to lower sperm counts—the study team is quick to stress you can’t draw that conclusion due to a lack of concrete data.

“We have much less data from non-Western studies, especially in the early period,” lead researcher Hagai Levine told Popular Science. “And since our model requires enough data, it’s difficult to assess the trends over time in the non-Western countries.”

While research has linked lifestyle habits like binge drinking, smoking, and obesity with male infertility, Levine says our first plan of action should be to flag new chemicals that could potentially squash our swimmers.

“Because male fertility and sperm count are very susceptible to the environment, it’s a great model to study the modern environment’s impact on human health,” he told PopSci. “Before we introduce new chemicals into the market, we need to properly test them and regulate their use. We need to measure their impact and eliminate use of certain chemicals that are shown to be very harmful.”