Mobile phones are exposing people to low-level electromagnetic energy in ways that are "unprecedented in human history".
So says University of Newcastle senior lecturer Geoffry De Iuliis, who is researching the effects of this energy on sperm.
"I'm sure many people have thought or worried about the potential constant exposure from mobile use at some point," Dr De Iuliis said.
"There is a need to get to the bottom of this."
He said the penetration of mobile technologies into many aspects of our lives had provided "huge advances for society".
"However, there is still public concern about the potential health impacts of using mobile devices.
"A large part of the concern I think stems from the fact that we are now using our devices for calls or internet access for large chunks of our days and lives."
At present, there is inadequate information in the debate around mobile devices and health risks.
Dr De Iuliis said there was a "real lack of understanding of how the very low energy electromagnetic fields" could interact with biological systems.
These fields are used for communication between devices and WiFi access-point or phone towers, he said.
"This gap in our collective understanding is a very important aspect to nail down if we are to be confident that indeed these technologies are safe.
"I've heard and read many arguments that go along the lines of 'there is no known mechanism, therefore it must be safe'."
He said this was a "pretty flawed statement".
"This unanswered question about the mechanism of action is what inspires us to carry out this work.
"We hope we can contribute in a meaningful way towards finding an answer."
Dr De Iuliis is leading a $425,000 research project, funded this year by the National Health and Medical Research Council.
The project aims to determine the biological effects on sperm of radio frequency electromagnetic energy emitted from mobile phones.
A description of the project states that "mobile phones have become an integral part of our lives".
"They rely on radiofrequency electromagnetic energy to communicate information.
"Despite the ever-growing exposure of our population to this form of energy, the potential effects on biological systems have not been resolved."
These potential effects were "currently under active debate".
"For this project, we are exposing sperm cells to various electromagnetic energy profiles that simulates our environmental exposures from mobile devices," Dr De Iuliis said.
"We then look to see if there are any visible or chemical changes in the cells, as a result of the exposures.
"The equipment we use for these studies has been custom designed and built via a collaboration between the University of Newcastle and University of NSW."
Exposure of sperm to electromagnetic energy has been shown to have negative effects.
"Our previous work and indeed the work currently being completed in our lab does show that exaggerated exposures can visibly affect sperm cells," he said.
This exposure can cause a decline in the movement of sperm and damage to their DNA.
"One of the things this has highlighted for us, is that the sperm cells are very sensitive to electromagnetic energy, as well as being a very convenient cell type to use for this research.
"Therefore, we think we have the perfect model to study the effects of electromagnetic energy on biology more deeply."
He said the main goal was to "work towards identifying a mechanism of action and to inform a potential risk to male fertility".
"We have approximated the exposures that reflect the levels a person may receive and are following some strong leads from that work.
"But there is still a lot of research to be done before we can confirm any cause for concern."
More recently, the research has found that "finely-tuned chemical balances within the sperm cells can be disturbed by the applied electromagnetic fields".
"We have gained more evidence that the sperm cell damage we observe is caused by molecules called 'reactive oxygen species'."
This typically causes a cell to enter a state of "oxidative stress".
"We are now trying to work out how the electromagnetic energy exposures produce these molecules inside sperm," he said.
He said sperm cells were "a very unique cell type" and the "smallest human cell".
Their unique properties mean they become particularly vulnerable to oxidative stress that is induced by radiofrequency electromagnetic energy.
"Other cell types in the body are usually more tolerable to this stress."
He said it would be interesting to see in future studies "if we can also detect similar changes in other cell types due to electromagnetic energy".
As for where males should store their mobile phone, he said it "can't hurt to try and keep the device away" from testicles, "especially if you are trying for a baby".
"We hope that the research we are doing in this space will allow us to offer some recommendations down the track.
"One of the causes for relief around male reproduction is that there is a huge production rate of sperm in the testes, around a 1000 per second."
This provides the opportunity to "replenish the pool, so to speak".
"However, this does not necessarily circumvent issues that may arise from other chronic factors that could impact sperm quality."
Dr De Iuliis said another area of research being pursued in reproductive medicine was "why some men produce poor quality sperm and therefore have fertility issues".
"One key finding we have made is that a man with fertility problems will produce a large proportion of sperm that show signs of oxidative stress," he said.
"In a similar fashion to our electromagnetic energy study, if we can understand the cause of this stress, we can then develop better therapies for these men who may depend on IVF to father a child."
He said antioxidants are used to combat oxidative stress.
"There is already a lot of work around using antioxidant molecules to combat sperm oxidative stress, including work here in Newcastle.
"However, taking off-the-shelf antioxidants has failed to show any improvements in IVF circles so far."
Many women change their lifestyle before they become pregnant, such as drinking or smoking less to help ensure a healthy pregnancy.
Men, too, should pay attention to their health when trying for a baby.
"It has been well established that men's health is strongly linked to fertility," Dr De Iuliis said.
"Certainly the clear example of this is the quite significant negative impacts smoking has on sperm quality.
"We are now understanding that obesity may also play a significant role in reducing sperm quality."
His research group, like others worldwide, was "certainly interested in the potential of using semen quality as a marker of a man's general health".
"There is a strong view in the field that the quality of the sperm cell that ultimately fertilises the egg is of great importance," he said.
It was important for the pregnancy and the future health of the child, "including the child's reproductive health".
The healthier the parents, the more likely sperm and egg quality will be higher and the better likelihood of a successful pregnancy and healthy children.
Age also plays a significant role, more so for women, but sperm quality does "inherently decline with a man's age".
"We know that having a healthy lifestyle does contribute to better sperm quality, but it is certainly not the whole story."
Boxers or Briefs
Sperm-underwear research that the Harvard T. H. Chan School of Public Health released last year included tests on 656 men.
It found that men who most frequently wore boxers had "significantly higher sperm concentrations and total sperm counts when compared with men who did not usually wear boxers".
Dr De Iuliis said heating the testes does lead to poorer sperm.
"This is why some fertility professionals recommend boxer shorts," he said.
The Harvard school also found couples who ate more fish were more likely to conceive and men who used marijuana had significantly higher concentrations of sperm.