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- Member of: Shinya Inoue
Heat exposure for urban populations has become more prevalent as the temperature and duration of heat waves in cities increase. Occupational exposure to heat is a major concern for personal health, and excessive heat exposure can cause devastating outcomes. While occupational heat exposure studies have traditionally focused on environmental temperature, work intensity, and clothing, little is known about the daily exposure profile of workers, including their daily travel and working patterns. This study developed a novel measure of exposure and reprieve dynamics, the moving average hourly exposure (MAHE) to balance short-duration but high-exposure events and capture the inability to reprieve from exposure events. MAHE was assessed by combining an activity-based travel model (ABM) and the Occupational Requirement Survey to simulate urban workers' total daily heat exposure. The simulation considers daily travel, work schedules, and outdoor working frequency. The simulation was conducted for 1 million workers in Phoenix, Arizona, using Mean Radiant Temperature (MRT). The results show that 53% to 89% of workers in Phoenix's construction, agriculture, transportation, raw material extraction, and entertainment industries will likely experience MAHE over 38°C for at least an hour. These industries also have up to 34% of the laborers exposed to over 7 hours of continuous 38°C and above MAHE exposure. The location of the most intense heat exposure was identified near the downtown and central business districts, significantly different from the home locations of the workers in suburban and rural areas. Formulating the MAHE balances heat risk events with cooling benefits and aids in identifying individuals with prolonged high heat exposure.
The City of Phoenix Street Transportation Department partnered with the Rob and Melani Walton Sustainability Solutions Service at Arizona State University (ASU) and researchers from various ASU schools to evaluate the effectiveness, performance, and community perception of the new pavement coating. The data collection and analysis occurred across multiple neighborhoods and at varying times across days and/or months over the course of one year (July 15, 2020–July 14, 2021), allowing the team to study the impacts of the surface treatment under various weather conditions.
Background:
Environmental heat exposure is a public health concern. The impacts of environmental heat on mortality and morbidity at the population scale are well documented, but little is known about specific exposures that individuals experience.
Objectives:
The first objective of this work was to catalyze discussion of the role of personal heat exposure information in research and risk assessment. The second objective was to provide guidance regarding the operationalization of personal heat exposure research methods.
Discussion:
We define personal heat exposure as realized contact between a person and an indoor or outdoor environment that poses a risk of increases in body core temperature and/or perceived discomfort. Personal heat exposure can be measured directly with wearable monitors or estimated indirectly through the combination of time–activity and meteorological data sets. Complementary information to understand individual-scale drivers of behavior, susceptibility, and health and comfort outcomes can be collected from additional monitors, surveys, interviews, ethnographic approaches, and additional social and health data sets. Personal exposure research can help reveal the extent of exposure misclassification that occurs when individual exposure to heat is estimated using ambient temperature measured at fixed sites and can provide insights for epidemiological risk assessment concerning extreme heat.
Conclusions:
Personal heat exposure research provides more valid and precise insights into how often people encounter heat conditions and when, where, to whom, and why these encounters occur. Published literature on personal heat exposure is limited to date, but existing studies point to opportunities to inform public health practice regarding extreme heat, particularly where fine-scale precision is needed to reduce health consequences of heat exposure.
Hot Playgrounds and Children's Health: A Multiscale Analysis of Surface Temperatures in Arizona, USA
Objectives: To provide novel quantification and advanced measurements of surface temperatures (Ts) in playgrounds, employing multiple scales of data, and provide insight into hot-hazard mitigation techniques and designs for improved environmental and public health.
Methods: We conduct an analysis of Ts in two Metro-Phoenix playgrounds at three scales: neighborhood (1 km resolution), microscale (6.8 m resolution), and touch-scale (1 cm resolution). Data were derived from two sources: airborne remote sensing (neighborhood and microscale) and in situ (playground site) infrared Ts (touch-scale). Metrics of surface-to-air temperature deltas (Ts–a) and scale offsets (errors) are introduced.
Results: Select in situ Ts in direct sunlight are shown to approach or surpass values likely to result in burns to children at touch-scales much finer than Ts resolved by airborne remote sensing. Scale offsets based on neighbourhood and microscale ground observations are 3.8 ◦C and 7.3 ◦C less than the Ts–a at the 1 cm touch-scale, respectively, and 6.6 ◦C and 10.1 ◦C lower than touch-scale playground equipment Ts, respectively. Hence, the coarser scales underestimate high Ts within playgrounds. Both natural (tree) and artificial (shade sail) shade types are associated with significant reductions in Ts.
Conclusions: A scale mismatch exists based on differing methods of urban Ts measurement. The sub-meter touch-scale is the spatial scale at which data must be collected and policies of urban landscape design and health must be executed in order to mitigate high Ts in high-contact environments such as playgrounds. Shade implementation is the most promising mitigation technique to reduce child burns, increase park usability, and mitigate urban heating.
Abstract:
Cascading failures across a network propagate localized issues to more broad and potentially unexpected failures in the network. In power networks, where load must be delivered in real-time by a generation source, network layout is an important part of cascading failure analysis. In lieu of real power network data protected for security reasons, we can use synthetic networks for academic purposes in developing a validating methodology. A contingency analysis technique is used to identify cascading failures, and this involves randomly selecting initial failure points in the network and observing how current violations propagate across the network. This process is repeated many times to understand the breadth of potential failures that may occur, and the observed trends in failure propagation are analyzed and compared to generate recommendations to prevent and adapt to failure. Emphasis is placed on power transmission networks where failures can be more catastrophic.
Syngas fermentation, the bioconversion of CO, CO[subscript 2], and H[subscript 2] to biofuels and chemicals, has undergone considerable optimization for industrial applications. Even more, full-scale plants for ethanol production from syngas fermentation by pure cultures are being built worldwide. The composition of syngas depends on the feedstock gasified and the gasification conditions. However, it remains unclear how different syngas mixtures affect the metabolism of carboxidotrophs, including the ethanol/acetate ratios. In addition, the potential application of mixed cultures in syngas fermentation and their advantages over pure cultures have not been deeply explored. In this work, the effects of CO[subscript 2] and H[subscript 2] on the CO metabolism by pure and mixed cultures were studied and compared. For this, a CO-enriched mixed culture and two isolated carboxidotrophs were grown with different combinations of syngas components (CO, CO:H[subscript 2], CO:CO[subscript 2], or CO:CO[subscript 2]:H[subscript 2]).
Results
The CO metabolism of the mixed culture was somehow affected by the addition of CO[subscript 2] and/or H[subscript 2], but the pure cultures were more sensitive to changes in gas composition than the mixed culture. CO[subscript 2] inhibited CO oxidation by the Pleomorphomonas-like isolate and decreased the ethanol/acetate ratio by the Acetobacterium-like isolate. H[subscript 2] did not inhibit ethanol or H[subscript 2] production by the Acetobacterium and Pleomorphomonas isolates, respectively, but decreased their CO consumption rates. As part of the mixed culture, these isolates, together with other microorganisms, consumed H[subscript 2] and CO[subscript 2] (along with CO) for all conditions tested and at similar CO consumption rates (2.6 ± 0.6 mmol CO L[superscript −1] day[superscript −1]), while maintaining overall function (acetate production). Providing a continuous supply of CO by membrane diffusion caused the mixed culture to switch from acetate to ethanol production, presumably due to the increased supply of electron donor. In parallel with this change in metabolic function, the structure of the microbial community became dominated by Geosporobacter phylotypes, instead of Acetobacterium and Pleomorphomonas phylotypes.
Conclusions
These results provide evidence for the potential of mixed-culture syngas fermentation, since the CO-enriched mixed culture showed high functional redundancy, was resilient to changes in syngas composition, and was capable of producing acetate or ethanol as main products of CO metabolism.
