We were already worried about keeping hotel keycards in the same pocket as our cell phones, but it turns out that our devices might be erasing some slightly more important things. Namely, men’s sperm.

In a new study, fertility experts claim that men who keep their mobiles anywhere near their reproductive organs — in their front pants pocket, for example — “may bear adverse effects on sperm concentration.” The scientists also found some correlations between lower sperm counts and talking on the phone for more than one hour a day and using the phone while it is charging.

The study, called “Habits of cell phone usage and sperm quality – Does it warrant attention?” appears in the journal Reproductive BioMedicine Online. The scientists involved were from the Division of Fertility at Carmel Medical Center in Haifa, Israel and include Ariel Zilberlicht, the chief resident of that department. These are just preliminary findings, and the researchers call for a broader-scale study, so you may not need to consider wrapping your iPhone or Galaxy Edge in tin foil just yet.

For starters, that might just cook the phone instead of your sperm.

Still, the results are interesting.

“We analysed the amount of active swimming sperm and the quality and found that it had been reduced,” Professor Martha Dinfield said (via the Telegraph). “We think this is being caused by a heating of the sperm from the phone and by electromagnetic activity.”

Dinfield and the other researchers studied 106 men who filled out questionnaires about their phone usage. Talking on their phones for more than one hour a day and using the device while it was charging resulted in a 25 to 30 percent higher incidence of “abnormal semen concentration” than the World Health Organization’s criteria for fertility as of 2010.

This isn’t the first time someone’s warned us that our favorite tech might be killing us (or our junk); we’ve heard for years that the heat from a laptop might lower sperm count, phones might cause brain tumors, and taking a call while pumping gas will have you dancing in the flames.

But correlation isn’t causation, and the scientists who conducted this research don’t know for sure if phones are raining down sperm death with heat and radiation. But it’s something to consider if you’re especially concerned with your fertility.