Men just about everywhere will be crossing their legs and groaning in despair when they learn that their trusted friend, the laptop computer, has become the latest threat to their manhood.
Just months after they were warned that carrying mobile phones in their pockets might damage their sperm count, men now have to absorb the news that laptops can similarly threaten their fertility.
Under the title "Increase in scrotal temperature in laptop computer users," researchers yesterday revealed in the journal Human Reproduction that a combination of the heat generated by the computers and the position of the thighs needed to balance the machines leads to higher temperatures around men's genitals.
Yefim Sheynkin, who led the research team from the State University of New York at Stonybrook, said it was possible that years of heavy laptop use "may cause irreversible or partially reversible changes in male reproductive function."
Until there was further research, teenage boys and young men might want to limit the use of computers on their laps, he said.
Past studies have suggested higher scrotal temperatures can damage sperm and affect fertility. Pesticides, smoking, obesity, prolonged car driving and tight trousers had all been blamed for diminishing male potency while the mobile phone theory was suggested by Hungarian scientists this summer.
Sheynkin said, however, that except for an anecdotal report of genital burns, the effect of portable computers on scrotal temperature had not been known.
"Laptops can reach internal operating temperatures of over 70?C. They are frequently positioned close to the scrotum, as well as being capable of producing direct local heat, they require the user to sit with his thighs close together to balance the machine, trapping the scrotum," he said.