Heat related illnesses are one of the leading causes of weather-related mortality in the United States, and heat extremes continue to increase in frequency and duration. Public health interventions include population mobility, including travel to central cooling centers or wellness checks on vulnerable populations. Using anonymized cellphone data from Safegraph’s neighborhood patterns dataset and gridded temperature data from gridMET, we explored the mobility-temperature relationship in the San Francisco Bay Area at fine spatial and temporal scale. We leveraged spatial variability in median income and temporal variability in COVID-19 related policies across two summers (2020-2021) to analyze their influence on the mobility-temperature relationship. We completed quantile regressions for a dataset stratified by income and year. We found that mobility increased at a higher rate with higher temperatures in 2020 than 2021. However, in 2021, the relationship reversed for several wealthier income groups, where mobility decreased with higher temperatures. We then augmented the analysis and calculated a panel regression with fixed effects to characterize the mobility-temperature relationship while controlling for temporal and spatial variability. This analysis suggested that all areas exhibited lower mobility with higher summer temperatures. However, similar to the results of the quantile regression, the rate of decrease in mobility in response to high temperature was significantly greater among the wealthiest census block groups compared with the least wealthy. Given the fundamental difference in the mobility response to temperature across income groups, our results are relevant for heat mitigation efforts in highly populated regions in current and future climate conditions.

Floating communities exist throughout the world. Many live on water with a high pathogen load due to difficulties associated with sewage management. In Claverito, an informal floating community in Iquitos, Peru, we conducted a controlled experiment to test the ability of water hyacinth (Eichhornia crassipes) to remove Escherichia coli from water. When river E. coli concentrations were at or below ~1500 CFU 100 mL-1, water hyacinth reduced shallow concentrations (8-cm depth) down to levels deemed safe by U.S. EPA for recreational use. Above this threshold, plants were able to reduce E. coli levels within shallow water, but not down to “safe” levels. At deeper depths (>25 cm), there was evidence that plants increased E. coli concentrations. Water hyacinth removed E. coli from shallow water by providing a surface (i.e., submerged roots) onto which pathogens sorbed and by protecting organisms that consume E. coli. Unfortunately, because of root association, the total E. coli load within the water column was greater with water hyacinth present, and results hinted that the plants’ protective environment also harbored parasites. The use of water hyacinth to keep surface water around floating communities low in E. coli could be beneficial as this is the water layer with which people most likely interact. Aquatic vegetation naturally proliferates in and around Claverito. While this study was based on curating aquatic plants in order to achieve a water-quality outcome, it nonetheless supports concrete actions for Claverito residents under non-curated conditions, which are outlined at the end of the manuscript.