Men using a cellular phone for more than one hour a day double the risk of their sperm count dropping to levels too low for procreation, according researchers from the Haifa Technion and the Carmel Medical Center.

A new study conducted at the two institutions, and published Tuesday in the medical journal Reproductive BioMedicine Online, brings evidence to support a long-feared link between dropping fertility rates in men and the prevalent use of cellular phones.

The quality of sperm among men in Western countries is constantly decreasing and is considered crucial in 40 percent of the cases in which couples have difficulty conceiving a child.

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The researchers, led by Dr. Ariel Zilberlicht of the Carmel Medical Center, investigated the link between characteristics of cellphone usage and semen quality by studying the phone habits of men referred for semen analysis.

According to the findings, sperm counts dropped to levels that can cause infertility among men who kept their phones half a meter (c. 2 feet) or less from their groins. Forty-seven percent of those who kept their phone in their pants pockets throughout the day recorded abnormally low levels of semen concentration, compared to only 11% of the general male population.

Talking on a cellphone for over an hour a day or speaking on the device when it is being charged doubles the risk for low semen concentration, the study found.

“In light of the results of the study it is certainly recommended [that men] shorten the duration of calls and avoid carrying the device near their groins, sleeping next to it, speaking on it when it’s charging (it is in fact recommended to turn it off when it’s charging) and use headphones or a headset as much as possible,” Zilberlicht was quoted by Channel 2 as saying.

Researchers said that more surveys covering larger groups of people would be necessary in order to point definitively at the damage cellular radiation can cause to male fertility.

An official from the sperm bank at Asuta, a chain of Israeli outpatient facilities, said that it was not clear-cut that dropping male fertility was related to the growing use of phones and the radiation they cause, but added that “we all have a gut feeling that there is a direct link, whether it be from cellphones or other types of radiation.”

Radiation from cellular phones and especially cellular towers, the relay stations that enable phones to be portable and maintain good reception over vast areas, has also been blamed by scientists in the past for an alarming drop in the global population of bees. That development, they fear, could spark a chain reaction leading to the extinction of plants relying on bees to carry their pollen and fertilize them.