Individual-level studies with adjustment for important COVID-19 risk factors suggest positive associations of long-term air pollution exposure (particulate matter and nitrogen dioxide) with COVID-19 infection, hospitalisations and mortality. The evidence, however, remains limited and mechanisms unclear. We aimed to investigate these associations within UK Biobank, and to examine the role of underlying chronic disease as a potential mechanism. UK Biobank COVID-19 positive laboratory test results were ascertained via Public Health England and general practitioner record linkage, COVID-19 hospitalisations via Hospital Episode Statistics, and COVID-19 mortality via Office for National Statistics mortality records from March–December 2020. We used annual average outdoor air pollution modelled at 2010 residential addresses of UK Biobank participants who resided in England (n = 424,721). We obtained important COVID-19 risk factors from baseline UK Biobank questionnaire responses (2006–2010) and general practitioner record linkage. We used logistic regression models to assess associations of air pollution with COVID-19 outcomes, adjusted for relevant confounders, and conducted sensitivity analyses. We found positive associations of fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) with COVID-19 positive test result after adjustment for confounders and COVID-19 risk factors, with odds ratios of 1.05 (95% confidence intervals (CI) = 1.02, 1.08), and 1.05 (95% CI = 1.01, 1.08), respectively. PM 2.5 and NO 2 were positively associated with COVID-19 hospitalisations and deaths in minimally adjusted models, but not in fully adjusted models. No associations for PM₁₀ were found. In analyses with additional adjustment for pre-existing chronic disease, effect estimates were not substantially attenuated, indicating that underlying chronic disease may not fully explain associations. We found some evidence that long-term exposure to PM_2.5 and NO₂ was associated with a COVID-19 positive test result in UK Biobank, though not with COVID-19 hospitalisations or deaths.

Urban greenspace provides opportunities for outdoor exercise and may increase physical activity, with accompanying health benefits. Areas suitable for walking (walkability) are also associated with increased physical activity, but interactions with greenspace are poorly understood. We investigated associations of walkability and green walkability with physical activity in an urban adult cohort. We used cross-sectional data from Greater London UK Biobank participants (n = 57,726) and assessed walkability along roads and footpaths within 1000 m of their residential addresses. Additionally, we assessed green walkability by integrating trees and low-lying vegetation into the walkability index. Physical activity outcomes included self-reported and accelerometer-measured physical activity and active transport. We assessed associations using log-linear, logistic and linear regression models, adjusted for individual- and area-level confounders. Higher green walkability was associated with favourable International Physical Activity Questionnaire responses and achievement of weekly UK government physical activity guideline recommendations. Participants living in the highest versus lowest quintile of green walkability participated in 2.41 min (95% confidence intervals: 0.22, 4.60) additional minutes of moderate-and-vigorous physical activity per day. Higher walkability and green walkability scores were also associated with choosing active transport modes such as walking and cycling. Our green walkability approach demonstrates the utility in accounting for walkability and greenspace simultaneously to understand the role of the built environment on physical activity.

The household sanitation target during the Millennium Development Goal (MDG) period used a binary “Improved”/”Unimproved” metric to evaluate progress. The “Unimproved” category was divided into three service levels: Shared Sanitation (facilities acceptable), Unimproved Facilities, and Open Defecation (no facility). Despite these data being publicly available, no analysis of country-level progress across these sanitation service levels during the MDGs has been published. We propose that retrospective analysis of progress across service levels can illuminate the diverse approaches used to address particular urban and rural sanitation deficits, and may provide insight to national and global actors in their ongoing efforts to address household sanitation. Additionally, we propose that a Sanitation Ladder Score, weighted to ascribe full, partial, and no credit to use of improved, shared and unimproved, and open defecation, respectively, is essential for concise communication of progress. Our analysis required gap-filling of data missing from the Joint Monitoring Programme (JMP) dataset; our final dataset consists of 190 countries representing 99.8% of global population. 149 countries achieved greater progress on the Sanitation Ladder Score than on the MDG metric. Using the four JMP progress categories, 144 countries fell into the same progress category and 41 achieved a higher category of Ladder Score progress. Countries with large gains in shared sanitation tended to have much greater progress on the Sanitation Ladder Score than on the MDG metric. A more detailed analysis is reported for six countries, with insight from the literature into their approaches. This Sanitation Ladder Score could be modified to incorporate the new “Safely Managed” service level tracked under the Sustainable Development Goals (SDGs) and likewise could be modified for other SDG targets for which multiple levels of service/achievement are reported. We encourage others to build upon our analysis; our complete dataset is freely available online (https://melliott.people.ua.edu/data.html).