Spatiotemporal variability of air pollutant concentrations and individuals' mobility are likely to play an important role in health outcomes and, therefore, time–activity-based exposure assessments are likely to be more sensitive compared to static residence-based air pollution estimates. Applied research on the effects of the variability underlying air pollutant concentrations and individuals' mobility on personal exposure estimates remain limited, however. We demonstrate how consideration of individuals' mobility and the spatiotemporal variability of ambient air pollution affect personal exposure estimates using both real-world data and simulated environmental conditions. Our findings suggest that time–activity-based exposure estimates might be quite similar to static estimates if spatiotemporal patterns of air pollution concentration surfaces lack autocorrelation or if an individual has a low level of mobility. There can be substantial differences, though, between two approaches when the air pollution concentrations are characterized by a model of air pollution that shows low variation over time and space and individuals' time spent away from home is substantial.

The origins of many large-scale 'biogenic' earthen structures are controversial, because often the species that built them have vanished. This is especially true when they form regular (over-dispersed), self-organized vegetation patterns [1]. Here, we describe a vast array of soil mounds constructed by termites (Syntermes dirus) that has persisted for up to 4000 years and covers an estimated 230,000 km2 of seasonally dry tropical forest in a relatively undisturbed and climatically stable region of Northeast Brazil. The mounds are not nests, but rather they are generated by the excavation of vast inter-connecting tunnel networks, resulting in approximately 10 km3 of soil being deposited in 200 million conical mounds that are 2.5 m tall and approximately 9 m in diameter. S. dirus termites are still present in the soil surrounding the mounds and we found that intra-specific aggression occurred at a scale much larger than an individual mound. We suggest that the complex network of tunnels built to access episodic leaf-fall has allowed for the optimization of waste soil removal, which over thousands of years has formed an over-dispersed spatial pattern of mounds.