Use of Twitter data to improve Zika virus surveillance in the United States during the 2016 epidemic

​BMC Public Health - June, 2019

Zika virus (ZIKV) is an emerging mosquito-borne arbovirus that can produce serious public health consequences. In 2016, ZIKV caused an epidemic in many countries around the world, including the United States. ZIKV surveillance and vector control is essential to combating future epidemics. However, challenges relating to the timely publication of case reports significantly limit the effectiveness of current surveillance methods. In many countries with poor infrastructure, established systems for case reporting often do not exist. Previous studies investigating the H1N1 pandemic, general influenza and the recent Ebola outbreak have demonstrated that time- and geo-tagged Twitter data, which is immediately available, can be utilized to overcome these limitations.


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Development of spatiotemporal models to predict ambient ozone and NOx concentrations in Tianjin, China

Atmospheric Environment - May, 2019

Nitrogen oxides (NOx) and ozone (O3) are important air pollutants that are associated with adverse health effects. Land-use regression (LUR) models have been widely developed to estimate air pollution concentrations. Due to data availability, however, such models are usually not applied in developing countries. We aimed to characterize NOx and O3 concentrations and develop LUR models to predict their spatial and temporal distributions using publicly-available data in Tianjin, a heavily polluted city in China. Seasonal samples were collected across Tianjin at 29 locations for O3 and 49 locations for NOx. Heavy-duty vehicle counts estimated from 0.5 m × 0.5 m satellite images correlated well with field-measured counts, thus supporting the use of high-resolution satellite images to assess vehicle traffic. Concentrations of NOx were highest in winter, while the opposite pattern was observed for O3. 


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Cardiovascular diseases in middle aged and older adults in China: the joint effects and mediation of different types of physical exercise and neighborhood greenness and walkability

Environmental Research, November 2018

Both physical exercise and the built environment are associated with cardiovascular diseases(CVDs). Yet, the influence of the multiple dimensions of the built environment and different types of physical exercise on CVDs is not well understood. Further, little is known about the joint effects of physical exercise and the built environment, nor whether one mediates the effect of the other on the risk of CVDs. We aim to investigate the risk of CVDs on middle aged and older Chinese adult populations by analyzing the independent effects, as well as potential interactions and mediation effects of different types of physical exercise and two dimensions of the built environment; namely, greenness and walkability.


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May Source characterization and exposure modeling of gas-phase polycyclic aromatic hydrocarbon (PAH) concentrations in Southern California

Atmospheric Environment - February, 2018 

Airborne exposures to polycyclic aromatic hydrocarbons (PAHs) are associated with adverse health outcomes. Because personal air measurements of PAHs are labor intensive and costly, spatial PAH exposure models are useful for epidemiological studies. However, few studies provide adequate spatial coverage to reflect intra-urban variability of ambient PAHs. In this study, we collected 39–40 weekly gas-phase PAH samples in southern California twice in summer and twice in winter, 2009, in order to characterize PAH source contributions and develop spatial models that can estimate gas-phase PAH concentrations at a high resolution.

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Use of Visual Range Measurements to Predict PM2.5 Exposures in Southwest Asia and Afghanistan

Journal of the Air & Waste Management Assoc. - October, 2016 
Military personnel deployed to Southwest Asia and Afghanistan were exposed to high levels of ambient particulate matter (PM) indicating the potential for exposure-related health effects. However, historical quantitative ambient PM exposure data for conducting epidemiological health studies are unavailable due to a lack of monitoring stations. Since visual range is proportional to particle light extinction (scattering and absorption), visibility can serve as a surrogate for PM2.5 concentrations where ground measurements are not available. We used data on visibility, relative humidity (RH), and PM2.5 ground measurements collected in Kuwait from years 2004 to 2005 to establish the relationship between PM2.5 and visibility.


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A novel calibration approach using satellite and visibility observations to estimate PM2.5 exposures in Southwest Asia and Afghanistan
Journal of the Air & Waste Management Assoc., September, 2016 

In order to study effects of ambient particulate matter (PM) it was previously necessary to have access to a comprehensive air monitoring network. However, there are locations in the world where PM levels are above generally accepted exposure standards but lack a monitoring infrastructure. This is true in Iraq and other locations in Southwest Asia and Afghanistan where U.S. and other coalition troops were deployed beginning in 2001. Since aerosol optical depth (AOD), determined by satellite, and visibility are both highly related to atmospheric PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) concentrations, we employed a novel approach that took advantage of historic airport visibility measurements to calibrate the AOD-visibility relationship and determine visibility spatially and temporally (2006-2007) over an approximately 17,000 km squared region of Iraq. 


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Composition and Sources of Fine and Coarse Particles Collected during 2002–2010 in Boston, MA
Journal of the Air & Waste Management Association - February, 2015
Identifying the sources, composition, and temporal variability of fine (PM2.5) and coarse (PM2.5–10) particles is a crucial component in understanding particulate matter (PM) toxicity and establishing proper PM regulations. In this study, a Harvard Impactor was used to collect daily integrated fine and coarse particle samples every third day for 9 years at a single site in Boston, MA. In total, 1,960 filters were analyzed for elements, black carbon (BC), and total PM mass. Positive Matrix Factorization (PMF) was used to identify source types and quantify their contributions to ambient PM2.5 and PM2.5–10.


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