ArticleFrontiers in public health2026
COVID-19 social interventions were associated with amplified, not attenuated, indoor source pollutant-respiratory health associations: a six-year time-series analysis in Xi'an, China.
Article in Frontiers in public health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
0 citing papers in PubMed.
No citing paper in PubMed yet.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
5 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Background: The COVID-19 pandemic triggered unprecedented social interventions that altered ambient air quality, population behavior, and healthcare-seeking. Whether these interventions modified the short-term association between air pollutants and respiratory health, and in which direction, remains unclear. Methods: We conducted a time-series study of daily respiratory outpatient visits (ICD-10: J00-J99, R04-R07, and R09) from a tertiary hospital in Xi'an, China, from January 2020 to December 2025. The study period was stratified into three COVID-19 phases: strict control (2020-2022), transition (Jan-Jun 2023), and post-pandemic (Jul 2023-2025). Generalized additive models with quasi-Poisson regression evaluated associations between PM2.5, SO2, NO2, and O3 and outpatient visits, adjusting for meteorological confounders, temporal trends, and phase. Pollutant-by-phase interaction terms tested for effect modification. Results: A total of 2,052,777 respiratory outpatient visits were recorded over 2,192 days. In full-period models, SO2 (lag4: ER = 9.11, 95% CI: 3.86-14.64%) and NO2 (lag5: ER = 2.72, 95% CI: 2.05-3.40%) showed the strongest associations. Phase-stratified analysis showed that the SO2 association was stronger during the strict control period (ER = 18.40, 95% CI: 10.29-27.11%) than the post-pandemic period (ER = 2.91, 95% CI: -4.82-11.28%), and the NO2 association followed the same pattern (3.07% vs. 1.31%). Formal interaction tests supported this gradient (SO2 × phase Conclusion: Contrary to the assumption that lockdowns would uniformly attenuate pollution-health effects, the health associations of combustion-source pollutants (SO2, NO2) in Xi'an were consistently stronger during strict COVID-19 control than the post-pandemic period, though formal interaction tests did not reach statistical significance. This pattern is consistent with, but does not confirm, an indoor exposure amplification mechanism in which prolonged home confinement increased cumulative exposure to residential heating emissions. These findings should be regarded as hypothesis-generating and indicate that reduced outdoor air pollution does not automatically translate into reduced health risk when population behavior changes substantially.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.