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1.1 – CitiSense: Improving Geospatial Environmental Assessment of Air Quality Using a Wireless Personal Exposure Monitoring System
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1.1 – CitiSense: Improving Geospatial Environmental Assessment of Air Quality Using a Wireless Personal Exposure Monitoring System


Tuesday, October 23, 2012 …

Tuesday, October 23, 2012
Technical Session #1

Nima Nikzad (University of California, San Diego, US), Nakul Verma (UCSD, US), Celal Ziftci (UCSD, US), Elizabeth Bales (UCSD, US), Nichole Quick (UCSD, US), Piero Zappi (UCSD, US), Kevin Patrick (UCSD, US), Sanjoy Dasgupta (UCSD, US), Ingolf Krueger (UCSD, US), Tajana Rosing (UCSD, US), William Griswold (UCSD, US)

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  • It is estimated that purely genetic factors account for the development of only 10-15% of diseases, and that environmental factors and lifestyle choices play a significant role in the development of other diseases. The exposome was a term first coined by Christopher Wild in 2005 to describe an individual’s lifetime worth of exposure to environmental factors and lifestyle choices. A better understanding of the exposome, studied along with the genome, will yield improvements in our understanding of how diseases are developed.
  • An example of the impact of exposure is the development of asthma. Studies have shown that asthma cases are more prevalent in populations located near highways. What is alarming is that more than 30% of our public schools are located within 400m of a highway. It is not surprising that we have so many respiratory events in our children each year. And while we are starting to figure out that being near these busy roadways is not good for our health, we still don’t understand which pollutants associated with traffic are especially bad for our health.
  • The EPA requires local government agencies to monitor the quality of air in the region. The number and types of sensors are based on the size of the region, it’s population, and any regional issues such as smog in southern california. San Diego county, for example, encompasses a region of over 4000 sq miles and has a population over 3 million. Only 10 monitoring sites track ozone and pm for the entire region. The data from these sites are used to generate air quality maps such as this, where green represents good air, yellow is moderate. However, this is not actionable data for an individual. This map does not tell me what I as an individual, living and working in the UCSD area, am actually being exposed to. REGIONAL SUMMARIES are not adequate for understanding what INDIVIDUALS are being exposed to. We can do better.
  • An individual that is interested in better understanding what they are being exposed to can…
  • CitiSense consists of three main components: an air pollution monitoring device, a mobile phone application, and a back-end server.The wireless device is worn on or near the body and contains sensors for carbon monoxide, nitrogen dioxide, ozone, temperature, humidity, and barometric pressure. It streams readings over bluetooth to a user’s mobile phone, where our application computes the Air Quality Index for the readings and presents a large, color coded number to the user. The user can then view the individual pollutants that contributed to their score and do things like share interesting readings on Facebook.The data is compressed and uploaded to our back-end server, and a user can bring up a web page that allows them to view a map of their exposure from throughout the day.
  • We deployed Citisense in a month long study, using two groups of eight people. All users were recruited from the UCSD community through mailing lists and included students, faculty, and staff. A wide variety of transportation methods were represented in the study, and primary requirement was that each user have a commute of at least 20 minutes, each direction. Users were asked to carry a provided smartphone and sensor whenever traveling around. Let’s take a look at some of the data collected by these users.
  • Here we have charts of data from March 15th and April 16th of this year. The solid black line represents the reported air quality from the nearest EPA monitoring site to the UCSD campus, and the colored points represent the measured air quality by each of our users.
  • Motivated individuals may identify hotspots of pollution in their communityAlert government agencies  Quickly address source of issues, provide guidance
  • Real-time always-on participatory sensing systems like CitiSense have the potential to revolutionize public health by enabling citizens to collect data that institutions cannot collect on their own


  • 1. CitiSense: Improving Geospatial Environmental Assessment of Air Quality Using a Wireless Personal Exposure Monitoring System Nima Nikzad, Nakul Verma, Celal Ziftci, Elizabeth Bales, Nichole Quick†, Piero Zappi, Kevin Patrick†, Sanjoy Dasgupta,Ingolf Krueger, Tajana Šimunić Rosing, and William G. GriswoldDept of Computer Science and Engineering, †School of Medicine University of California, San Diego Wireless Health 2012 – October 23rd, 2012
  • 2. Disease is Primarily Non-Genetic 85% Genetic 15% Other Controllable factors account for most diseases  Other: Environmental, lifestyle, and multifactorial “Exposome” – Environmental exposures over an individual’s lifetime [Wild, 2005]  Along with genome  Improves understanding of disease 2
  • 3. Impact of Environmental Exposure USA Today, 10/1/2009 Asthma events are 50% higher near highways  30% of public schools are near highways  350,000 – 1,300,000 respiratory events in children annually Diesel exhaust  Carcinogens, long-term impact Peak exposure Cardiac events, hospital admission 3
  • 4. Current State of Air Quality Monitoring EPA requires local agencies to monitor air quality for their region  Required number of exposure monitoring is not adequate. are The current state of sensors, monitored pollutants based on region size, population, regional issues Regional air quality summaries are not sufficient. We require a better understanding of what individuals are actually being exposed to. sq. mi. 4000 3.1M residents 10 monitoring sites for San Diego County! 4
  • 5. Participatory Sensing of the Environment contribute CitiSense EPA distribute5
  • 6. CitiSense: System Overview Air Pollution Sensor CitiSense Smartphone App CO, NO2, O3, H umidity, Pressur e, Temp Back-end Server Upload Measurements6
  • 7. User Study of Individual Exposure Conducted a month-long user study (Spring 2012)  16 users (two groups of eight users each) Recruited from the UCSD community  Students, faculty, and staff  Variety of commuting methods: car, bus, bicycle, motorized scooter, trolley, and train  Commute at least 20 minutes each direction Each user was asked to carry a provided smartphone and CitiSense sensor everyday  Compensated $75 for time, travel costs at conclusion 7
  • 8. Individual Exposure vs. Regional SummaryUnhealthyUnhealthy for S.G.Moderate GoodMarch 15th, 2012 8
  • 9. Data Enables Finer Grained Maps User reported AQI measurements Simple interpolation during a 5-minute window starting (using standard geostatistical at 4:27PM PST, April 16th 2012 kriging techniques)9
  • 10. Implications for Public Health Deploying CitiSense in a community could:  Improve measurement of individual exposure  Monitor cumulative impact of this exposure on regional health outcomes  Provide feedback to highly-sensitive users, community  Advance our understanding of the exposome 10
  • 11. Opportunities and Challenges Improved modeling techniques  Machine learning techniques  Tag readings with user-context, activity Sensor calibration  Keeping sensors calibrated in the field  Detecting, correcting faulty sensors Energy management on devices  Localization, networking, processing  power hungry  Minimize impact on user’s smartphone battery lifeWebsite: https://sosa.ucsd.edu/confluence/display/CitiSensePublic/CitiSense 11
  • 12. Conclusion Using CitiSense, measurements of individual exposure found to vary significantly from reported regional summaries Better understanding the exposome will lead to a better understanding of disease etiology and revolutionize the practice of public health The cumulative impact of many individuals using personal sensing devices may have an important role to play in the future of environmental measurement for public health 12
  • 13. Air Quality Index13
  • 14. System Architecture: Rich Services14
  • 15. User Observations “… just by walking through a high bus area exposes you to unhealthy air (more than I would have thought).” “… surprised how it spikes to yellow, red, or purple anytime I go near a busy street.” “One of the things that was surprising was how sort of local the pollution is.”https://sosa.ucsd.edu/confluence/display/CitiSensePublic/CitiSense 15
  • 16. Impact of Understanding the Exposome Better understanding the exposome has the potential to revolutionize the practice of public health Enable individuals to make healthier Drive public policy choices16