Predicting the microbial exposure risks in urban floods using GIS, building simulation, and microbial models

London is expected to experience more frequent periods of intense rainfall and tidal surges, leading to an increase in the risk of flooding. Damp and flooded dwellings can support microbial growth, including mould, bacteria, and protozoa, as well as persistence of flood-borne microorganisms. The amount of time flooded dwellings remain damp will depend on the duration and height of the flood, the contents of the flood water, the drying conditions, and the building construction, leading to particular properties and property types being prone to lingering damp and human pathogen growth or persistence. The impact of flooding on buildings can be simulated using Heat Air and Moisture (HAM) models of varying complexity in order to understand how water can be absorbed and dry out of the building structure. This paper describes the simulation of the drying of building archetypes representative of the English building stock using the EnergyPlus based tool ‘UCL-HAMT’ in order to determine the drying rates of different abandoned structures flooded to different heights and during different seasons. The results are mapped out using GIS in order to estimate the spatial risk across London in terms of comparative flood vulnerability, as well as for specific flood events. Areas of South and East London were found to be particularly vulnerable to long-term microbial exposure following major flood events

Simulation of pollution transport in buildings: the importance of taking into account dynamic thermal effects

The recent introduction of the Generic Contaminant Model in EnergyPlus allows for the integrated modelling of multizone contaminant and dynamic thermal behaviour within a single simulation package. This article demonstrates how dynamic thermal simulation can modify pollutant transport within a building. PM2.5 infiltration from the external to internal environment under dynamic thermal conditions is compared in CONTAM, EnergyPlus 8.0, and Polluto, an in-house pollutant transport model developed in EnergyPlus 3.1. The influence of internal temperature on indoor PM2.5 levels is investigated by comparing results from standard CONTAM simulations and dynamic thermal EnergyPlus 8 simulations. Circumstances where the predictions of such models can diverge are identified

Using building simulation to model the drying of flooded building archetypes

With a changing climate, London is expected to experience more frequent periods of intense rainfall and tidal surges, leading to an increase in the risk of flooding. This paper describes the simulation of the drying of flooded building archetypes representative of the London building stock using the EnergyPlus-based hygrothermal tool ‘University College London-Heat and Moisture Transfer (UCL-HAMT)’ in order to determine the relative drying rates of different built forms and envelope designs. Three different internal drying scenarios, representative of conditions where no professional remediation equipment is used, are simulated. A mould model is used to predict the duration of mould growth risk following a flood on the internal surfaces of the different building types. Heating properties while keeping windows open dried dwellings fastest, while purpose built flats and buildings with insulated cavity walls were found to dry slowest

Developmental changes in hypoxic exposure and responses to anoxia in Drosophila melanogaster

© 2015. Published by The Company of Biologists Ltd. Holometabolous insects undergo dramatic morphological and physiological changes during ontogeny. In particular, the larvae of many holometabolous insects are specialized to feed in soil, water or dung, inside plant structures, or inside other organisms as parasites where they may commonly experience hypoxia or anoxia. In contrast, holometabolous adults usually are winged and live with access to air. Here, we show that larval Drosophila melanogaster experience severe hypoxia in their normal laboratory environments; third instar larvae feed by tunneling into a medium without usable oxygen. Larvae move strongly in anoxia for many minutes, while adults (like most other adult insects) are quickly paralyzed. Adults survive anoxia nearly an order of magnitude longer than larvae (LT50: 8.3 versus 1 h). Plausibly, the paralysis of adults is a programmed response to reduce ATP need and enhance survival. In support of that hypothesis, larvae produce lactate at 3× greater rates than adults in anoxia. However, when immobile in anoxia, larvae and adults are similarly able to decrease their metabolic rate, to about 3% of normoxic conditions. These data suggest that Drosophila larvae and adults have been differentially selected for behavioral and metabolic responses to anoxia, with larvae exhibiting vigorous escape behavior likely enabling release from viscous anoxic media to predictably normoxic air, while the paralysis behavior of adults maximizes their chances of surviving flooding events of unpredictable duration. Developmental remodeling of behavioral and metabolic strategies to hypoxia/anoxia is a previously unrecognized major attribute of holometabolism

Housing as a modifier of air contaminant and temperature exposure in Great Britain: A modelling framework

This paper presents the development of a modelling framework that quantifies the modifying effect of dwelling characteristics on exposure to indoor air pollution and excess temperature. A georeferenced domestic building stock model of Great Britain was created using national housing surveys, historical weather, and local terrain data. Dynamic building performance simulation was applied to estimate indoor air pollution and overheating risk metrics at the individual building level. These metrics were then aggregated at various geographic units and mapped across Britain within a Geographic Information System (GIS) environment to compare spatial trends. Results indicate that flats and newly built properties are characterised by lower indoor air pollution from outdoor sources, but higher air pollution from indoor sources. Flats, bungalows and newly built, more airtight dwellings are found to be more prone to overheating. Consequently, urban populations may experience higher levels of pollution from indoor sources and overheating resulting from the higher prevalence of flats in cities

Mapping indoor overheating and air pollution risk modification across Great Britain: A modelling study

Housing has long been thought to play a significant role in population exposure to environmental hazards such as high temperatures and air pollution. However, there is sparse data describing how housing may modify heat and air pollution exposure such that housing's role in poor health and mortality from these hazards may be estimated. This paper describes the development of individual-address level indoor overheating and air pollution risk modifiers for Great Britain, for use alongside historical weather, outdoor air pollution, population socio-economic data, and mortality data in a large-scale epidemiological investigation. A geographically-referenced housing stock database was developed using the Homes Energy Efficiency Database (HEED) and the English Housing Survey (EHS). Simulations of unique combinations of building, fabric, occupation, and environment were run using a modelling framework developed for EnergyPlus 8.0, estimating indoor temperature metrics, indoor/outdoor ratio of pollution from outdoor sources, and indoor air pollution from multiple indoor sources. Results were compiled, matched back to individual properties in HEED, and mapped using Geographical Information Systems (GIS). Results indicate urban areas had higher numbers of buildings prone to overheating, reduced levels indoor air pollution from outdoor sources, and higher air pollution from indoor sources relative to rural areas, driven largely by variations in building types. The results provide the first national-scale quantitative estimate of heat and indoor air pollution modification by dwellings, aggregated at levels suitable for inclusion in health analysis

The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources.

UNLABELLED: A number of studies have estimated population exposure to PM2.5 by examining modeled or measured outdoor PM2.5 levels. However, few have taken into account the mediating effects of building characteristics on the ingress of PM2.5 from outdoor sources and its impact on population exposure in the indoor domestic environment. This study describes how building simulation can be used to determine the indoor concentration of outdoor-sourced pollution for different housing typologies and how the results can be mapped using building stock models and Geographical Information Systems software to demonstrate the modifying effect of dwellings on occupant exposure to PM2.5 across London. Building archetypes broadly representative of those in the Greater London Authority were simulated for pollution infiltration using EnergyPlus. In addition, the influence of occupant behavior on indoor levels of PM2.5 from outdoor sources was examined using a temperature-dependent window-opening scenario. Results demonstrate a range of I/O ratios of PM2.5 , with detached and semi-detached dwellings most vulnerable to high levels of infiltration. When the results are mapped, central London shows lower I/O ratios of PM2.5 compared with outer London, an apparent inversion of exposure most likely caused by the prevalence of flats rather than detached or semi-detached properties. PRACTICAL IMPLICATIONS: Population exposure to air pollution is typically evaluated using the outdoor concentration of pollutants and does not account for the fact that people in London spend over 80% of their time indoors. In this article, building simulation is used to model the infiltration of outdoor PM2.5 into the domestic indoor environment for dwellings in a London building stock model, and the results mapped. The results show the variation in relative vulnerability of dwellings to pollution infiltration, as well as an estimated absolute indoor concentration across the Greater London Authority (GLA) scaled by local outdoor levels. The practical application of this work is a better understanding of the modifying effect of the building geometry and envelope design on pollution exposure, and how the London building stock may alter exposure. The results will be used to inform population exposure to PM2.5 in future environmental epidemiological studies

A novel post-processing contaminant transport and decay model for EnergyPlus

This paper introduces PolyPol, a post-processing tool that calculates the transport and deposition of an unlimited number of contaminants from airflow data output from EnergyPlus simulations. In addition, the model is able to use data on temperature and humidity-related airborne pathogen decay or chemical reaction rates to estimate the loss or gain of species over time. An initial intermodel validation between the EnergyPlus Generic Contaminant Model, CONTAM, and PolyPol is performed, and the importance of dynamic indoor temperatures and water vapour concentration demonstrated. PolyPol is then used to model influenza levels in a pre and post-energy efficient retrofit terraced dwelling, accounting for building thermal, moisture, and ventilative behaviour, and biological decay