What's more, the ability of the sperm to swim properly was also found to be impaired, particularly among men who made long calls.Not everyone accepts the evidence as conclusive, however. The good news is that he believes external protective devices could help.MOBILE PHONESAnother fertility scare came from the University of Szeged in Hungary, which claimed mobile phones could lower sperm counts by up to a third because of the radiation they emit. "They are frequently placed 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," explains Yefim Sheynkin from the State University of New York at Stony Brook, who led the study. It is well known that sperm production drops if the environment within the testicles becomes too hot, which is why they are housed outside the main part of the body.The study, published in the journal Human Reproduction, found that laptops can reach internal operating temperatures of over 70C.

"We know from other studies that there is no relationship between exposure to traffic fumes and reduced fertility of men living in urban areas compared with men living in rural areas," he says. "If the study suggests anything - a relatively small number of men took part in it - then it's that men would have to be exposed to very high levels before their fertility was affected."LAPTOPSYears of using a laptop regularly "may cause irreversible or partially irreversible changes in male reproductive function", according to one study. Italian researchers found taxi drivers, truckers and other professional drivers all had reduced fertility levels. Another study by French researchers found that even driving for two hours can raise testicle temperature by around 2C."he increase in scrotal temperature we measured in drivers could be one of the strongest pieces of evidence to explain why the partners of occupational drivers take longer to conceive," says Dr Roger Mieusset, the head of the research group. You can minimise the damage by taking hourly breaks from the wheel for 10 minutes.TRAFFIC POLLUTIONYou don't have to actually drive a car to put your fertility at risk. Scientists believe that nitrogen oxide and lead in exhaust fumes may be to blame.

Dr Michele De Rosa and her colleagues at the University of Naples in Italy examined the sperm of 85 men employed at motorway tollgates who, on average, were exposed to traffic fumes six hours a day. They were found to have poorer sperm quality and less active sperm than men of the same age, living in the same area, who were not exposed to traffic pollution.But Professor Harry Moore of Sheffield University, who is carrying out the biggest study yet to examine the impact of chemicals in the environment on male fertility, is sceptical. Here are some of the other things that scientists believe may have an effect on male fertility...FAST FOODIf you happen to be partial to convenience or fast food - which is often packed full of "hidden soy" - you may be heading for a host of fertility problems. Scientists believe chemicals in the soya bean mimic oestrogen.Dr Sheena Lewis, who conducted the latest research, says chemicals found in soya appear to lower sperm count and affect the ability of sperm to swim. "The results concern us," she says.DRIVINGA mounting body of evidence reveals that sitting behind the wheel for long periods is bad for sperm. But on the day of their IVF treatment, the man has had little or no sperm at all because he's had a bad bout of flu," says Dr Iwan Lewis-Jones, a consultant andrologist at the Liverpool Women's Hospital and an expert in male infertility. In fact, enhancements may help retain natural oils.Men can have manicures too.