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The authors stated in the Discussion that "In addition, physical distancing and other public health interventions were introduced nationwide in England during the first epidemic, mitigating any distortion between air-pollution and COVID-19 mortality due to potential regional level differences." Moreover, the public health message from this study, and others like it, is that outdoor air pollution increases mortality rates of COVID-19 thereby suggesting to some that going outdoors will increase infections. As we indicated in our review ([17]), bias from this under ascertainment can be appreciable and will likely vary by socioeconomic status of regions and the capacity of each area to test and treat COVID-19 that will covary with concentrations of air pollution ([7]). Many of the following comments are generic to most studies of COVID-19 and air pollution which we have discussed at length in our methodological paper in Environmental Health Perspectives ([17]) as well as in another critique of a recent paper ([8]). [Extracted from the article]

Abstract: In the UK, excessive levels of radon gas have been detected in domestic housing. Areas where 1% of existing homes were found to be over the Action Level of 200Bq·m−3 were declared to be Radon Affected Areas. Building Regulations have been introduced which require that, for areas where between 3% and 10% of existing houses are above the Action Level, new homes should be built with basic radon protection using a membrane, and that, where 10% or more of existing homes exceed this level, new homes should be built with full radon protection. Initially these affected areas followed administrative boundaries, known as Counties. However, with increasing numbers of measurements of radon levels in domestic homes recorded in the national database, these areas have been successively refined into smaller units – 5km grid squares in 1999, down to 1km grid squares in 2007. One result is the identification of small areas with raised radon levels within regions where previously no problem had been identified. In addition, some parts of areas that were previously considered radon affected are now considered low, or no, risk. Our analysis suggests that the net result of improved mapping is to increase the number of affected houses. Further, the process is more complex for local builders, and inspectors, who need to work out whether radon protection in new homes is appropriate. Our group has assessed the cost-effectiveness of radon remediation programmes, and has applied this analysis to consider the cost-effectiveness of providing radon protection in both new and existing homes. This includes modelling the potential failure rate of membranes, and whether testing radon levels in new homes is appropriate. The analysis concludes that it is more cost effective to provide targeted radon protection in high radon areas, although this introduces more complexity. The paper also considers the trend in housing to a greater proportion of apartments, the regional variations in types of housing and the decreasing average number of occupants in each dwelling, and concludes that data and methods are now available to respond to the health risks of radon at a local level, in keeping with a general initiative to prioritise responses to health and social welfare issues at a more local level. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Within-house and within-room spatial temporal variability in PBDE contamination of indoor dust may influence substantially the reliability of human exposure assessments based on single point samples, but have hitherto been little studied. This paper reports concentrations of PBDEs 17, 28, 47, 49, 66, 85, 99, 100, 153, and 154 in indoor dust samples (n=112) from two houses in Birmingham, UK. To evaluate within-house spatial variability, four separate rooms were sampled in house 1 and two separate rooms sampled in house 2. Up to four different 1m2 areas in the same room were sampled to evaluate within-room spatial variability, and for all studied areas, samples were taken for eight consecutive months to evaluate temporal and seasonal variability. Concentrations of ΣPBDEs in individual samples from house 1 varied between 21 and 280ngg−1; while the range of concentrations in house 2 was 20–1000ngg−1. This indicates that where and when a sample is taken in a house can influence substantially the contamination detected. In one room, concentrations of PBDEs in an area located close to putative PBDE sources exceeded substantially those in an area 2m away, with marked differences also observed between two areas in another room. Substantial within-room spatial differences in PBDE concentrations were not discernible in the other rooms studied. Concentrations of PBDEs in the majority of rooms within the same houses were not markedly different between rooms. Nevertheless, large differences were observed between PBDE concentrations detected in two rooms in the same house in both houses studied. In one instance, this is hypothesised to be attributable to the presence of a carpet in one room and bare wooden floor in another, but firm conclusions cannot be drawn. Within-room temporal (month-to-month) variability was substantial (relative standard deviations for ΣPBDEs=15–200%). In some rooms, the introduction and removal of putative sources like a TV and a bed, appeared to exert a discernible influence on PBDE concentrations. PBDE concentrations in spring and summer were not markedly different from those observed in autumn and winter. Possible dilution of PBDE concentrations in dust at higher dust loadings (g dust per m2 floor surface) was investigated in a small number of rooms, but no firm evidence of such dilution was evident. [Copyright &y& Elsevier]