To help clarify whether radio-frequency electromagnetic radiation from mobile phones can cause male fertility problems, researchers at the University of Exeter reviewed ten separate studies.
Sperm quality was assessed by measuring motility (movement), viability (number of sperm that are alive) and concentration of sperm cells in semen, all of which are commonly used in the clinic to assess fertility. The researchers found that while a control group had 50 to 80 percent normal movement, exposure to mobile phones led to an eight percent drop in average motility. Mobile phones also led to a nine percent drop in viability. The effects on concentration were however unclear.
'This study strongly suggests that being exposed to radio-frequency electromagnetic radiation from carrying mobiles in trouser pockets negatively affects sperm quality', said lead researcher Dr Fiona Mathews.
The studies that were analysed looked at a total of 1,492 samples from men attending fertility clinics and research centres, and comprised of both experimental in vitro and observational in vivo studies.
However, the study has come under criticism, with many pointing out that the results from such meta-analyses can be problematic if the individual studies have inconsistencies.
Professor Neil McClure, professor of obstetrics and gynaecology at Queen's University Belfast, was not involved in the study. He said: 'This paper has taken a number of much smaller papers and grouped them together. However, the quality of data that has been pooled is flawed'.
'Subjects are often those who are already attending an infertility clinic and subjects have self-reported their use of mobile phones: it is not clear if this is continuous or intermittent usage. It would be difficult to see how holding a mobile phone to one's ear could have a significant pathological effect on sperm quality'.
Dr Allen Pacey, Senior Lecturer in Andrology at the University of Sheffield, has also raised concerns, saying: 'There have been some crazy and alarming headlines on this subject. But, in my opinion, the studies undertaken to date have been somewhat limited'.
The authors of the meta-analysis have however also been cautious to point out that more work is now needed. Dr Mathews said that 'further research is required to determine the full clinical implications for the general population'.
Speaking to the BBC, she added: 'This is interesting, but we're obviously not saying that everyone who carries a phone in their pocket is going to become infertile'.