## 4 Conclusions and Discussion
The health danger zones represent the space-time-behavior segments along an individual's space-time trajectory where his/her personal health impact from air pollution was high. It is very important to understand that these danger zones may not fully agree with the personal AQI color zones. This is because AQI reflects concentration of pollutant in the ambient air, but the health danger zones are tailored to reflect the health effect from pollutant intake. Even though the pollutant concentration may not be as high, certain space-time activities may create personal danger zones due to the need for significantly elevated air intake. The contributions of this study are mostly three-folds. First, time geography was extended to account for the dynamics of individual-environment interaction and was used as the framework for investigating the continuous change of personal exposure to and intake of air pollutant over space and time. Second, 3D maps were used to visualize personal exposure conditions. The 3D geovisualization modeled not only an individual's space-time path but also the changing dynamics of real-time personal AQI. Third, personal air pollution danger zones are defined and visualized along the personal space-time path to connect personal space-time behavior with personal health effects. Applying this approach to a future prediction of air pollution scenario, one can model personal air pollution danger zones for an individual's real or planned spatiotemporal activity trajectories. This can be used to assist an individual in selecting a spatiotemporal activity trajectory with the minimum adverse health effects. Therefore, the approach reported in this paper has a great potential in helping alleviate the adverse health effects of air pollution through managing individual-level space-time activities. However, some limitations from the study should be noticed. First, the data accuracy for the empirical study in the paper is limited due to sensor precision. The increment of the portable O\({}_{3}\) sampler was limited to 10 ppb, and any variation below this level was not detectable by the sensor. Second, the volunteer's pollutant intake was estimated based on the past empirical findings about general population's air inhalation rate. Future research should consider using portable breath sensor that can automatically and accurately record an individual's breathe rate. Last, the limitation of the data collection means used in the reported pilot study must be recognized. It is impractical to expect the general public to carry both a GPS and a pollutant sensor while conducting daily activities. As pointed out by [PERSON] and [PERSON] [9], the research on real-time assessment of personal air pollution exposure and health effects are limited by the availability of sensors that can genuinely integrate location-detection and air pollutant sampling technologies. This technological limitation has been one major restriction for most of on-going or not-fully-implemented projects seeking to link air sensor to GPS (such as those reviewed in [19]). The focus of this paper is on the integration, analysis, and visualization of the related data for the purpose of analyzing personal health effects and health danger zones from air pollution. It is by no means the purpose of this study to showcase a GIS and air sensor integrated data collection approach. This study pilots the investigation of personal air pollution exposure and intake, aiming at evaluating personal health effects of air pollution. Although only O\({}_{3}\) was investigated by the empirical study, the approach can be extended to other pollutants when proper sensors are available and health standard related AQIs are defined. Our next step of work will include continuous search for and design of an improved data collection means to support extending the individual-level health effects analysis and health danger zone modeling to the general public in order to serve people with varied backgrounds and different space-time behavior patterns.