The study, published in the journal Fertility and Sterility, said radio-frequency electromagnetic waves emitted from cell phones in talk mode may have a negative impact on the motility and viability of sperm cells.

Ashok Agarwal, head of the Center for Reproductive Medicine at clinic's Glickman Urological and Kidney Institute, said researchers collected semen samples from 32 subjects. Sperm specimens from the test group were placed 2.5 centimeters from a 850 MHz cell phone in talk mode for 1 hour --the typical distance between the testes and trouser pockets, the clinic said Thursday in a release.

The findings showed that cell phone radiation increased the amount of free radicals and decreased the amount of anti-oxidants in semen.

Agarwal, however, warned that more testing is needed. "Our study has not provided proof that you should stop putting cell phones in your pocket. There are many things that need to be proven before we get to that stage," he told CNN.