Adverse short-term effects of ozone on cardiovascular mortalities modified by season and temperature: a time-series study

Key factors in epidemiological exposure and insights for environmental management: Evidence from meta-analysis

In recent years, the precision of exposure assessment methods has been rapidly improved and more widely adopted in epidemiological studies. However, such methodological advancement has introduced additional heterogeneity among studies. The precision of exposure assessment has become a potential confounding factors in meta-analyses, whose impacts on effect calculation remain unclear. To explore, we conducted a meta-analysis to integrate the long- and short-term exposure effects of PM2.5, NO2, and O3 on all-cause, cardiovascular, and respiratory mortality in the Chinese population. Literature was identified through Web of Science, PubMed, Scopus, and China National Knowledge Infrastructure before August 28, 2023. Sub-group analyses were performed to quantify the impact of exposure assessment precisions and pollution levels on the estimated risk. Studies achieving merely city-level resolution and population exposure are classified as using traditional assessment methods, while those achieving sub-kilometer simulations and individual exposure are considered finer assessment methods. Using finer assessment methods, the RR (under 10 μg/m3 increment, with 95% confidence intervals) for long-term NO2 exposure to all-cause mortality was 1.13 (1.05-1.23), significantly higher (p-value = 0.01) than the traditional assessment result of 1.02 (1.00-1.03). Similar trends were observed for long-term PM2.5 and short-term NO2 exposure. A decrease in short-term PM2.5 levels led to an increase in the RR for all-cause and cardiovascular mortality, from 1.0035 (1.0016-1.0053) and 1.0051 (1.0021-1.0081) to 1.0055 (1.0035-1.0075) and 1.0086 (1.0061-1.0111), with weak between-group significance (p-value = 0.13 and 0.09), respectively. Based on the quantitative analysis and literature information, we summarized four key factors influencing exposure assessment precision under a conceptualized framework: pollution simulation resolution, subject granularity, micro-environment classification, and pollution levels. Our meta-analysis highlighted the urgency to improve pollution simulation resolution, and we provide insights for researchers, policy-makers and the public. By integrating the most up-to-date epidemiological research, our study has the potential to provide systematic evidence and motivation for environmental management.

Association of Ozone and Temperature with Ischemic Heart Disease Mortality Risk: Mediation and Interaction Analyses

Global warming and elevated ozone (O3) levels are gradually gaining widespread attention, and exposure to which may cause many physiological changes associated with cardiovascular events such as hypertension, cardiomyocyte apoptosis, etc. In addition, ischemic heart disease (IHD) is the leading cause of death worldwide. However, the contributions of temperature and O3, independently or in combination, to IHD mortality are not well understood. This study employs a two-stage analytical protocol (generalized additive model followed by meta-analysis) to explore the respective associations of temperature and O3 with IHD mortality, and determine their possible mediation and interaction effects. Our results suggest that increases of 10 μg/m3 in O3 and 1 °C in temperature at lag01 day are associated with increased IHD mortality risks of 0.789% and 0.686%, respectively. O3 can mediate the relationship between temperature and IHD mortality, with a pooled estimate of 0.140%, while temperature can mediate the association between O3 and IHD mortality, with a pooled estimate of 0.162%. The additive and multiplicative interaction effects of O3 and temperature were significantly associated with IHD mortality. The study findings demonstrate that higher temperature and O3 concentrations can increase human IHD mortality risk through interaction and mediation effects, providing a scientific basis for the synergistic management of temperature and O3 or associated interventions.

A bibliometric analysis of research on the health impacts of ozone air pollution

Ground-level ozone (O3) is one of the major air pollutants. A large body of literature has linked O3 air pollution to various adverse human health effects. The objective of this study is to attain a comprehensive and in-depth understanding of the progress and frontiers of research on O3 and human health. We used bibliometric methods to summarize publications on O3 air pollution and public health between 1990 and 2022 obtained from the Web of Science Core Collection database. VOSviewer and R software were used for bibliometric analysis and visualization. A total of 4501 relevant papers were included in the analysis. There has been a significant increase in the number of publications since 2013, with the USA being the major contributor, followed by China and England. Harvard University was the most prolific research institution, followed by the US Environmental Protection Agency and the University of North Carolina System. Professor Joel Schwartz was the most published author and has established a complex network of national and international collaborations. Co-occurrence analysis of keywords suggested evolving research hotspots, from toxicological studies to population-based epidemiological studies and from the respiratory system to the extra-pulmonary system. Research on O3 and its human health effects has progressed rapidly over the past few decades, but academic disparities still persist between developed and developing countries. There is an urgent need to strengthen international cooperation to address the public health challenges posed by rising O3 air pollution in the future.