The state of scientific evidence on air pollution and human health in Nepal

•Only 23 studies linking air pollution and health have been conducted in Nepal.•Most studies use indirect exposure assessment and focus on respiratory health.•Studies generally had short timeframes and few participants.•Exposure studies demonstrate higher pollution than in other parts of the world.•Further research needed with larger studies and more health outcomes.

Air pollution has been linked to acute and chronic health effects. However, the majority of evidence is based in North America and Europe, with a growing number of studies in Asia and Latin America. Nepal is one of the many South Asian countries where little such research has been conducted. We summarized the state of scientific evidence and identify research gaps based on the existing literature on air pollution and human health in Nepal. We performed a systematic literature search to identify relevant studies. Studies were categorized as those that estimate: (1) health impacts of indoor air pollution, (2) health impacts of outdoor air pollution, (3) health burdens from outdoor air pollution in Nepal based on existing concentration-response relationships from elsewhere, or (4) exposure and air quality but do not link to health. We identified 89 studies, of which 23 linked air pollution to health impacts. The remainder focused on exposure and air quality, demonstrating high pollution levels. The few health studies focused mainly on indoor air (n=15), especially in rural areas and during cooking. Direct exposure measurements were for short time periods; most studies used indirect exposure methods (e.g., questionnaire). Most health studies had small sample sizes with almost all focusing on respiratory health. Although few studies have examined air pollution and health in Nepal, the existing studies indicate high pollution levels and suggest large health impacts. Nepal's dearth of scientific research on air pollution and health is not unique and likely is similar to that of many other developing regions. Future research with larger studies and more health outcomes is needed. Key challenges include data availability.