Background: Environmental health is a growing area of knowledge, continually increasing and updating the body of evidence linking the environment to human health. Aim: This study summarizes the epidemiological evidence on environmental risk factors from meta-analyses through an umbrella review. Methods: An umbrella review was conducted on meta-analyses of cohort, case-control, case-crossover, and time-series studies that evaluated the associations between environmental risk factors and health outcomes defined as incidence, prevalence, and mortality. The specific search strategy was designed in PubMed using free text and Medical Subject Headings (MeSH) terms related to risk factors, environment, health outcomes, observational studies, and meta-analysis. The search was limited to English, Spanish, and French published articles and studies on humans. The search was conducted on September 20, 2020. Risk factors were defined as any attribute, characteristic, or exposure of an individual that increases the likelihood of developing a disease or death. The environment was defined as the external elements and conditions that surround, influence, and affect a human organism or population’s life and development. The environment definition included the physical environment such as nature, built environment, or pollution, but not the social environment. We excluded occupational exposures, microorganisms, water, sanitation and hygiene (WASH), behavioral risk factors, and no-natural disasters. Results: This umbrella review found 197 associations among 69 environmental exposures and 83 diseases and death causes reported in 103 publications. The environmental factors found in this review were air pollution, environmental tobacco smoke, heavy metals, chemicals, ambient temperature, noise, radiation, and urban residential surroundings. Among these, we identified 65 environmental exposures defined as risk factors and 4 environmental protective factors. In terms of study design, 57 included cohort and/or case-control studies, and 46 included time-series and/or case-crossover studies. In terms of the study population, 21 included children, and the rest included adult population and both sexes. In this review, the largest body of evidence was found in air pollution (91 associations among 14 air pollution definitions and 34 diseases and mortality diagnoses), followed by environmental tobacco smoke with 24 associations. Chemicals (including pesticides) were the third larger group of environmental exposures found among the meta-analyses included, with 19 associations. Conclusion: Environmental exposures are an important health determinant. This review provides an overview of an evolving research area and should be used as a complementary tool to understand the connections between the environment and human health. The evidence presented by this review should help to design public health interventions and the implementation of health in all policies approach aiming to improve populational health.

Purpose of Review The COVID-19 pandemic has impacted daily-life activities around the world. Multiple countries and cities are implementing different mitigation strategies to reduce their transmission (e.g., physical distancing, stay-at-home orders, avoiding large gatherings). Such interventions have been related to positive and negative health externalities. Currently, the selection of mitigation strategies has not been systematically considering a long-term vision for urban health equity. This review presents evidence and a framework linking COVID-19 mitigation strategies, the built environment, and transport to health determinants and outcomes. In addition, the paper provides a set of urban interventions aimed at supporting COVID-19 mitigation strategies and promoting a long-term health equity vision. Recent Findings COVID-19 mitigation strategies, in addition to helping reduce disease transmission, have also decreased urban road transport, resulting in indirect benefits on air quality, traffic noise, and traffic incidents. On the other hand, the same mitigation strategies have had negative impacts on physical activity, mental health, home isolation, and access to transport options, among others. COVID-19 mitigation strategies are an opportunity to test and implement built environment and transport interventions aimed to maximize health equity and minimize health risks. National and local authorities should systematically integrate a long-term urban health equity vision when designing and implementing COVID-19 mitigation strategies. Summary COVID-19 offers an opportunity to rethink the built environment and transport infrastructure with the aim to support short-term mitigation strategies and reduce long-term urban health inequities.

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