Health effects in people relocating between environments of differing ambient air pollution concentrations: A literature review.

People who relocate to a new environment may experience health effects from a change in ambient air pollution. We undertook a literature review of studies of such relocations and health effects and report the results as a narrative analysis. Fifteen articles of heterogeneous designs met the inclusion criteria. Four short-term (relocation duration less than six months) and three long-term (relocation duration six months or greater) studies reported evidence of the effect of relocation on physiological outcome, biomarkers or symptoms. All had potential weaknesses of design or analysis but, as a whole, their results are broadly consistent in suggesting short-term adverse effects of air pollutants or their reversibility. One long-term study provided evidence that changes in air pollution exposure during adolescence have a measurable effect on lung function growth. Four cohort studies were also identified that used relocation to strengthen evidence of air-pollution-exposure relationships by using a design that incorporates effective randomization of exposure or the use of relocation to improve exposure classification. However, three studies of relocation during pregnancy provided limited evidence to conclude an effect of relocation-related change in exposure on pregnancy outcome. Overall, most relocation studies are consistent with short- or long-term adverse effects of air pollution on biological function or mortality, but many studies of change in exposure have design weaknesses that limit the robustness of interpretation. We outline principles for improved design and analysis to help strengthen future studies for the insights they can provide from their quasi-experimental designs, including on the nature and timing of functional changes of relocation-related changes in exposure to ambient air pollution.

Personal exposure monitoring of PM2.5 among US diplomats in Kathmandu during the COVID-19 lockdown, March to June 2020.

The 2019 Novel Coronavirus SARS-CoV 2 (COVID-191) pandemic has severely impacted global health, safety, economic development and diplomacy. The government of Nepal issued a lockdown order in the Kathmandu Valley for 80 days from 24 March to 11 June 2020. This paper reports associated changes in ambient PM2.5 measured at fixed-site monitors and changes in personal exposure to PM2.5 monitored by APT Minima by four American diplomats who completed monitoring before and during lockdown (24 h for each period per person, 192 person-hours in total). Time activities and use of home air pollution mitigation measures (use of room air cleaners (RACs), sealing of homes) were recorded by standardized diary. We compared PM2.5 exposure level by microenvironment (home (cooking), home (other activities), at work, commuting, other outdoor environment) in terms of averaged PM2.5 concentration and the contribution to cumulative personal exposure (the product of PM2.5 concentration and time spent in each microenvironment). Ambient PM2.5 measured at fixed-sites in the US Embassy and in Phora Durbar were 38.2% and 46.7% lower than during the corresponding period in 2017-2019. The mean concentration of PM2.5 to which US diplomats were exposed was very much lower than the concentrations of ambient levels measured at fixed site monitors in the city both before and during lockdown. Within-person comparisons suggest personal PM2.5 exposure was 50.0% to 76.7% lower during lockdown than before it. Time spent outdoors and cooking at home were large contributors to cumulative personal exposure. Low indoor levels of PM2.5 were achieved at work and home through use of RACs and measures to seal homes against the ingress of polluted air from outside. Our observations indicate the potential reduction in exposure to PM2.5 with large-scale changes to mainly fossil-fuel related emissions sources and through control of indoor environments and activity patterns.