Health impacts of transportation and the built environment: A quantitative risk assessment

The design of urban transportation networks can affect three kinds of human health risks: (1) motor vehicle crashes, (2) air pollution from automobiles, and (3) physical inactivity occurring when motor vehicles replace walking and cycling as the main means of transportation. However, the relative magnitude of each of these risks in relation to the way cities are designed is poorly understood, and tools and methods that simultaneously assess all three risks are limited. Furthermore, available tools rely on static methods that fail to account for cumulative health impacts over time. This work developed the first dynamic micro-simulation model for quantifying all three risks and then applied the model to compare transportation health risks between neighborhood groups of varying designs within the Raleigh-Durham-Chapel Hill region. The model combines information on crash risk as a function of vehicle miles traveled, demographic and built environment variables routinely collected by the US Census Bureau, modeled estimates of fine particulate air pollution arising from traffic computed at the census block scale, and baseline public health data from the North Carolina State Center for Health Statistics in order to estimate premature mortality risks from each of the three transportation-risk sources at the census block group scale. The model estimates that the combined health impacts of transportation are lowest in block groups with designs that encourage walking for transportation (18.4 annual excess deaths per 100,000 persons on average over 10 years, compared to 22.9 in the least walkable block groups). While air pollution health impacts are higher in the most walkable block groups (2.14 annual excess deaths per 100,000 persons compared to 1.15), physical inactivity and crash risks are lower in these areas (2.70 annual excess deaths per 100,000 compared to 6.66 and 13.5 compared to 15.1, respectively). Similarly, net individual risks of premature mortality are lower among those who walk, bike, or ride transit to work due to increased physical activity and decreased risk of fatal crashes. These results illustrate that designing neighborhoods to encourage walking has important net health benefits.Doctor of Philosoph

The built environment, spatial variation in fine particulate matter concentrations, and attributable mortality: a scenario-based land use regression approach

A land use regression model is calibrated to predict annual average PM2.5 concentrations throughout the Triangle Region. A risk assessment model is used to predict attributable all-cause mortality from exposure to predicted concentrations. Two alternative land development scenarios are compared to current conditions in terms of air quality and health impacts. This study finds that compact development alone is not an effective intervention to reduce all-cause mortality attributable to fine particulate matter in urban areas; however, regional air quality improves in response to more compact development. While compact development patterns may reduce total vehicle-kilometers travelled and improve regional air quality, the combination of compact urban forms and automobile dependence may result in significant local air quality impacts co-located with area of high population density. Therefore, compact urban forms may exacerbate health impacts associated with fine particulate matter if other policy options to reduce automobile dependence are not simultaneously put forth.Master of City and Regional Plannin

Health Impacts of Increased Physical Activity from Changes in Transportation Infrastructure: Quantitative Estimates for Three Communities

Recently, two quantitative tools have emerged for predicting the health impacts of projects that change population physical activity: the Health Economic Assessment Tool (HEAT) and Dynamic Modeling for Health Impact Assessment (DYNAMO-HIA). HEAT has been used to support health impact assessments of transportation infrastructure projects, but DYNAMO-HIA has not been previously employed for this purpose nor have the two tools been compared. To demonstrate the use of DYNAMO-HIA for supporting health impact assessments of transportation infrastructure projects, we employed the model in three communities (urban, suburban, and rural) in North Carolina. We also compared DYNAMO-HIA and HEAT predictions in the urban community. Using DYNAMO-HIA, we estimated benefit-cost ratios of 20.2 (95% C.I.: 8.7–30.6), 0.6 (0.3–0.9), and 4.7 (2.1–7.1) for the urban, suburban, and rural projects, respectively. For a 40-year time period, the HEAT predictions of deaths avoided by the urban infrastructure project were three times as high as DYNAMO-HIA’s predictions due to HEAT’s inability to account for changing population health characteristics over time. Quantitative health impact assessment coupled with economic valuation is a powerful tool for integrating health considerations into transportation decision-making. However, to avoid overestimating benefits, such quantitative HIAs should use dynamic, rather than static, approaches

Azole Drugs Are Imported By Facilitated Diffusion in Candida albicans and Other Pathogenic Fungi

Despite the wealth of knowledge regarding the mechanisms of action and the mechanisms of resistance to azole antifungals, very little is known about how the azoles are imported into pathogenic fungal cells. Here the in-vitro accumulation and import of Fluconazole (FLC) was examined in the pathogenic fungus, Candida albicans. In energized cells, FLC accumulation correlates inversely with expression of ATP-dependent efflux pumps. In de-energized cells, all strains accumulate FLC, suggesting that FLC import is not ATP-dependent. The kinetics of import in de-energized cells displays saturation kinetics with a Km of 0.64 uM and Vmax of 0.0056 pmol/min/108 cells, demonstrating that FLC import proceeds via facilitated diffusion through a transporter rather than passive diffusion. Other azoles inhibit FLC import on a mole/mole basis, suggesting that all azoles utilize the same facilitated diffusion mechanism. An analysis of related compounds indicates that competition for azole import depends on an aromatic ring and an imidazole or triazole ring together in one molecule. Import of FLC by facilitated diffusion is observed in other fungi, including Cryptococcus neoformans, Saccharomyces cerevisiae, and Candida krusei, indicating that the mechanism of transport is conserved among fungal species. FLC import was shown to vary among Candida albicans resistant clinical isolates, suggesting that altered facilitated diffusion may be a previously uncharacterized mechanism of resistance to azole drugs

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

The Built Environment, Spatial Variation in Fine Particulate Matter Concentrations, and Attributable Mortality: A Scenario-Based Land Use Regression Approach

A land use regression model is calibrated to predict annual average PM[25] concentrations throughout the Triangle Region. A risk assessment model is used to predict attributable all-cause mortality from exposure to predicted concentrations. Two alternative land development scenarios are compared to current conditions in terms of air quality and health impacts. This study finds that compact development alone is not an effective intervention to reduce all-cause mortality attributable to fine particulate matter in urban areas; however, regional air quality improves in response to more compact development. While compact development patterns may reduce total vehicle-kilometers travelled and improve regional air quality, the combination of compact urban forms and automobile dependence may result in significant local air quality impacts co-located with area of high population density. Therefore, compact urban forms may exacerbate health impacts associated with fine particulate matter if other policy options to reduce automobile dependence are not simultaneously put forth

Estimating active transportation behaviors to support health impact assessment in the United States

Health impact assessment (HIA) has been promoted as a means to encourage transportation and city planners to incorporate health considerations into their decision-making. Ideally, HIAs would include quantitative estimates of the population health effects of alternative planning scenarios, such as scenarios with and without infrastructure to support walking and cycling. However, the lack of baseline estimates of time spent walking or biking for transportation (together known as active transportation), which are critically related to health, often prevents planners from developing such quantitative estimates. To address this gap, we use data from the 2009 US National Household Travel Survey to develop a statistical model that estimates baseline time spent walking and biking as a function of the type of transportation used to commute to work along with demographic and built environment variables. We validate the model using survey data from the Raleigh-Durham-Chapel Hill, NC, metropolitan area. We illustrate how the validated model could be used to support transportation-related HIAs by estimating the potential health benefits of built environment modifications that support walking and cycling. Our statistical model estimates that on average, individuals who commute on foot spend an additional 19.8 (95% CI 16.9–23.2) minutes per day walking compared to automobile commuters. Public transit riders walk an additional 5.0 (95% CI 3.5–6.4) minutes per day compared to automobile commuters. Bicycle commuters cycle for an additional 28.0 (95% CI 17.5–38.1) minutes per day compared to automobile commuters. The statistical model was able to predict observed transportation physical activity in the Raleigh-Durham-Chapel Hill region to within 0.5 MET-hours per day (equivalent to about 9 minutes of daily walking time) for 83% of observations. Across the Raleigh-Durham-Chapel Hill region, an estimated 38 (95% CI 15–59) premature deaths potentially could be avoided if the entire population walked 37.4 minutes per week for transportation (the amount of transportation walking observed in previous US studies of walkable neighborhoods). The approach developed here is useful both for estimating baseline behaviors in transportation HIAs and for comparing the magnitude of risks associated with physical inactivity to other competing health risks in urban areas