For example, masts could be used to measure rainfall in areas without rain gauges, according to a study published in the Proceedings of the National Academy of Sciences (PNAS) this month (4 February).
In the PNAS study, the researchers estimated average rainfall intensity from telecommunication network data for the Netherlands, taking advantage of the fact that rain causes signal losses between mobile-phone masts. They then compared these estimated rainfall maps with those generated from radar and rain gauges.
'There was a good match between the rainfall maps based on the mobile network and those based on the radar and rain gauge data,' says lead author Aart Overeem, a hydrologist with Wageningen University in the Netherlands and the Royal Netherlands Meteorological Institute.
The researchers say their findings could be applicable in Africa and other places that lack a reliable network of rain gauges.
They hope their study will persuade mobile-phone companies to release relevant data freely for use in research and to measure rainfall.
But Overeem adds that the rain-measuring technique must be studied further both over a longer period and in places, such as the tropics, where mobile-phone masts often operate at lower radio frequencies. At such frequencies, there is a more complex relationship between rain and signal weakening that could affect the accuracy of rainfall maps.
A further application for mobile-phone towers could be to divert some of their electricity supply to cool vaccines, says Harvey Rubin, professor of medicine at the University of Pennsylvania in the United States and a director of Energize the Chain (EtC), an organisation that aims to set up this refrigeration.
The power for masts comes from generators, electricity companies or renewable energy sources such as the wind, which is paid for by mast operators.
As part of an EtC project in Zimbabwe, telecommunications firm Econet Wireless Zimbabwe has provided mast-cooled vaccine refrigerators at more than 100 sites, Rubin says, adding that the organisation will be focusing on India and Kenya next.
'Through the EtC initiative, it costs just 60 US cents a day to run one of the World Health Organization-approved vaccine refrigerators in remote villages,' he says.
Judah Levine, an EtC director who is also chief executive officer of HIP Consult, a US-based firm with expertise in African telecommunications markets, says that masts in countries such as Ghana and Zambia are owned and operated by companies on behalf of mobile telecommunication firms, so it is important to get both tower and telecommunication operators on board.
But Amekugee Eugene Gameli, project manager at mobile mast firm Helios Towers Ghana, says that, although using towers to cool vaccines is innovative, guidelines on masts' positioning could hinder the idea's implementation. In Ghana, he says, mobile masts must be at least 400 metres from hospitals, making them less suitable for storing vaccines.
On masts' rainfall-mapping abilities, Gameli warned that their use in urban areas could lead to errors because pollution also contributes to signal loss between towers, which could be mistaken for rainfall.