Benefits of Mobile Phone Technology for Personal Environmental Monitoring.
BACKGROUND
Tracking individuals in environmental epidemiological studies using novel mobile phone technologies can provide valuable information on geolocation and physical activity, which will improve our understanding of environmental exposures.


OBJECTIVE
The objective of this study was to assess the performance of one of the least expensive mobile phones on the market to track people's travel-activity pattern.


METHODS
Adults living and working in Barcelona (72/162 bicycle commuters) carried simultaneously a mobile phone and a Global Positioning System (GPS) tracker and filled in a travel-activity diary (TAD) for 1 week (N=162). The CalFit app for mobile phones was used to log participants' geographical location and physical activity. The geographical location data were assigned to different microenvironments (home, work or school, in transit, others) with a newly developed spatiotemporal map-matching algorithm. The tracking performance of the mobile phones was compared with that of the GPS trackers using chi-square test and Kruskal-Wallis rank sum test. The minute agreement across all microenvironments between the TAD and the algorithm was compared using the Gwet agreement coefficient (AC1).


RESULTS
The mobile phone acquired locations for 905 (29.2%) more trips reported in travel diaries than the GPS tracker (P<.001) and had a median accuracy of 25 m. Subjects spent on average 57.9%, 19.9%, 9.0%, and 13.2% of time at home, work, in transit, and other places, respectively, according to the TAD and 57.5%, 18.8%, 11.6%, and 12.1%, respectively, according to the map-matching algorithm. The overall minute agreement between both methods was high (AC1 .811, 95% CI .810-.812).


CONCLUSIONS
The use of mobile phones running the CalFit app provides better information on which microenvironments people spend their time in than previous approaches based only on GPS trackers. The improvements of mobile phone technology in microenvironment determination are because the mobile phones are faster at identifying first locations and capable of getting location in challenging environments thanks to the combination of assisted-GPS technology and network positioning systems. Moreover, collecting location information from mobile phones, which are already carried by individuals, allows monitoring more people with a cheaper and less burdensome method than deploying GPS trackers.
ISGlobal, Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.|Pompeu Fabra University (UPF), Barcelona, Spain.|Ciber on Epidemiology and Public Health (CIBERESP), Barcelona, Spain.|Physical Activity and Sports Sciences Department, Fundació Blanquerna, Ramon Llull University, Barcelona, Spain.
David
http://orcid.org/0000-0003-2337-1712
D
Donaire-Gonzalez
ISGlobal, Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.|Pompeu Fabra University (UPF), Barcelona, Spain.|Ciber on Epidemiology and Public Health (CIBERESP), Barcelona, Spain.
Antònia
http://orcid.org/0000-0002-9275-7101
A
Valentín
Center for Environmental Policy, Imperial College London, London, United Kingdom.
Audrey
http://orcid.org/0000-0002-1092-3971
A
de Nazelle
ISGlobal, Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.|Pompeu Fabra University (UPF), Barcelona, Spain.|Ciber on Epidemiology and Public Health (CIBERESP), Barcelona, Spain.
Albert
http://orcid.org/0000-0002-7968-1747
A
Ambros
ISGlobal, Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.|Pompeu Fabra University (UPF), Barcelona, Spain.|Ciber on Epidemiology and Public Health (CIBERESP), Barcelona, Spain.
Glòria
http://orcid.org/0000-0002-8588-6722
G
Carrasco-Turigas
Department of Environmental and Occupational Health Services, University of Washington, Seattle, WA, United States.
Edmund
http://orcid.org/0000-0003-4058-0313
E
Seto
Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.|Department of Environmental Health, Fielding School of Public Health, University of California, Los Angeles, CA, United States.
Michael
http://orcid.org/0000-0002-4121-0587
M
Jerrett
ISGlobal, Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain.|Pompeu Fabra University (UPF), Barcelona, Spain.|Ciber on Epidemiology and Public Health (CIBERESP), Barcelona, Spain.
Mark J
http://orcid.org/0000-0001-9461-7981
MJ
Nieuwenhuijsen
automatic data processing; cell phones; environmental exposure; mobile applications; monitoring, ambulatory; smartphone; spatio-temporal analysis; travel