tetano
Editor, Senior Moderator
Environ Int
. 2026 Jan 24:208:110090.
doi: 10.1016/j.envint.2026.110090. Online ahead of print.
The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities
Keita Wagatsuma[SUP] 1 [/SUP], Denise Feurer[SUP] 2 [/SUP], Wenhua Yu[SUP] 3 [/SUP], Rongbin Xu[SUP] 3 [/SUP], Tim Riffe[SUP] 4 [/SUP], Maxi Stella Kniffka[SUP] 5 [/SUP], Enrique Acosta[SUP] 6 [/SUP], Ben Armstrong[SUP] 7 [/SUP], Malcolm Mistry[SUP] 8 [/SUP], Rachel Lowe[SUP] 9 [/SUP], Dominic Royé[SUP] 10 [/SUP], Masahiro Hashizume[SUP] 11 [/SUP], Aurelio Tobias[SUP] 12 [/SUP], Ana Maria Vicedo-Cabrera[SUP] 13 [/SUP], Lina Madaniyazi[SUP] 14 [/SUP], Chris Fook Sheng Ng[SUP] 15 [/SUP], Carmen Íñiguez[SUP] 16 [/SUP], Martina S Ragettli[SUP] 17 [/SUP], Eric Lavigne[SUP] 18 [/SUP], Patricia Matus Correa[SUP] 19 [/SUP], Nicolás Valdés Ortega[SUP] 19 [/SUP], Jan Kyselý[SUP] 20 [/SUP], Aleš Urban[SUP] 20 [/SUP], Hans Orru[SUP] 21 [/SUP], Ene Indermitte[SUP] 21 [/SUP], Marek Maasikmets[SUP] 22 [/SUP], Susanne Breitner-Busch[SUP] 23 [/SUP], Alexandra Schneider[SUP] 23 [/SUP], Yasushi Honda[SUP] 24 [/SUP], Barrak Alahmad[SUP] 25 [/SUP], Antonella Zanobetti[SUP] 25 [/SUP], Joel Schwartz[SUP] 25 [/SUP], Gabriela Carrasco[SUP] 26 [/SUP], Iulian Horia Holobâca[SUP] 27 [/SUP], Ho Kim[SUP] 28 [/SUP], Whanhee Lee[SUP] 29 [/SUP], Michelle L Bell[SUP] 30 [/SUP], Noah Scovronick[SUP] 31 [/SUP], Fiorella Acquaotta[SUP] 32 [/SUP], Micheline de Sousa Zanotti Stagliorio Coelho[SUP] 33 [/SUP], Magali Hurtado Diaz[SUP] 34 [/SUP], Eunice Elizabeth Félix Arellano[SUP] 34 [/SUP], Paola Michelozzi[SUP] 35 [/SUP], Massimo Stafoggia[SUP] 35 [/SUP], Francesca de'Donato[SUP] 35 [/SUP], Shilpa Rao[SUP] 36 [/SUP], Xerxes Seposo[SUP] 37 [/SUP], Shilu Tong[SUP] 38 [/SUP], Jochem Klompmaker[SUP] 39 [/SUP], Yuming Guo[SUP] 3 [/SUP], Pierre Masselot[SUP] 40 [/SUP], Antonio Gasparrini[SUP] 40 [/SUP], Francesco Sera[SUP] 41 [/SUP]
Affiliations
Several studies have explored the short-term effects of environmental stressors on coronavirus disease 2019 (COVID-19) transmission and severity. However, evidence on the interactive effects of meteorological conditions and air pollution remains limited and geographically variable. We therefore aimed to quantify the independent and interactive effects of short-term exposure to humidex, a composite index of temperature and relative humidity, and fine particulate matter ≤ 2.5 μm (PM[SUB]2.5[/SUB]) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM[SUB]2.5[/SUB] concentrations were collected from 439 cities in 22 countries during January 2020-August 2022 as part of the Multi-Country Multi-City Collaborative Research Network. A two-stage design was applied: first, city-specific quasi-Poisson models with distributed lag non-linear models estimated exposure-response associations; second, multilevel random-effects meta-analyses pooled city-specific estimates. Effect modification by PM[SUB]2.5[/SUB] was assessed using a product term between non-linear humidex function and linear PM[SUB]2.5[/SUB] function. Approximately 95.1 million confirmed COVID-19 cases were analyzed. Lower humidex values (0.1 °C versus 15.1 °C) were associated with increased daily cases (relative risk [RR]: 1.1192, 95% confidence interval [CI]: 1.0214-1.2262). A 10 μg/m[SUP]3[/SUP]increase in PM[SUB]2.5[/SUB] over the current and preceding 2 days was associated with a modest increase in daily cases (RR: 1.0079, 95% CI: 1.0001-1.0161). No statistically significant interaction between humidex and PM[SUB]2.5[/SUB] was observed. Short-term exposure to cold-dry conditions and elevated PM[SUB]2.5[/SUB] independently increased COVID-19 incidence, highlighting the need to consider both thermal environment and air quality when designing climate-resilient public health responses. These findings enhance understanding of how climate-related environmental stressors influence COVID-19 transmission.
Keywords: COVID-19; Effect modification; Humidex; MCC Collaborative Research Network; PM(2.5); Two-stage design.
. 2026 Jan 24:208:110090.
doi: 10.1016/j.envint.2026.110090. Online ahead of print.
The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities
Keita Wagatsuma[SUP] 1 [/SUP], Denise Feurer[SUP] 2 [/SUP], Wenhua Yu[SUP] 3 [/SUP], Rongbin Xu[SUP] 3 [/SUP], Tim Riffe[SUP] 4 [/SUP], Maxi Stella Kniffka[SUP] 5 [/SUP], Enrique Acosta[SUP] 6 [/SUP], Ben Armstrong[SUP] 7 [/SUP], Malcolm Mistry[SUP] 8 [/SUP], Rachel Lowe[SUP] 9 [/SUP], Dominic Royé[SUP] 10 [/SUP], Masahiro Hashizume[SUP] 11 [/SUP], Aurelio Tobias[SUP] 12 [/SUP], Ana Maria Vicedo-Cabrera[SUP] 13 [/SUP], Lina Madaniyazi[SUP] 14 [/SUP], Chris Fook Sheng Ng[SUP] 15 [/SUP], Carmen Íñiguez[SUP] 16 [/SUP], Martina S Ragettli[SUP] 17 [/SUP], Eric Lavigne[SUP] 18 [/SUP], Patricia Matus Correa[SUP] 19 [/SUP], Nicolás Valdés Ortega[SUP] 19 [/SUP], Jan Kyselý[SUP] 20 [/SUP], Aleš Urban[SUP] 20 [/SUP], Hans Orru[SUP] 21 [/SUP], Ene Indermitte[SUP] 21 [/SUP], Marek Maasikmets[SUP] 22 [/SUP], Susanne Breitner-Busch[SUP] 23 [/SUP], Alexandra Schneider[SUP] 23 [/SUP], Yasushi Honda[SUP] 24 [/SUP], Barrak Alahmad[SUP] 25 [/SUP], Antonella Zanobetti[SUP] 25 [/SUP], Joel Schwartz[SUP] 25 [/SUP], Gabriela Carrasco[SUP] 26 [/SUP], Iulian Horia Holobâca[SUP] 27 [/SUP], Ho Kim[SUP] 28 [/SUP], Whanhee Lee[SUP] 29 [/SUP], Michelle L Bell[SUP] 30 [/SUP], Noah Scovronick[SUP] 31 [/SUP], Fiorella Acquaotta[SUP] 32 [/SUP], Micheline de Sousa Zanotti Stagliorio Coelho[SUP] 33 [/SUP], Magali Hurtado Diaz[SUP] 34 [/SUP], Eunice Elizabeth Félix Arellano[SUP] 34 [/SUP], Paola Michelozzi[SUP] 35 [/SUP], Massimo Stafoggia[SUP] 35 [/SUP], Francesca de'Donato[SUP] 35 [/SUP], Shilpa Rao[SUP] 36 [/SUP], Xerxes Seposo[SUP] 37 [/SUP], Shilu Tong[SUP] 38 [/SUP], Jochem Klompmaker[SUP] 39 [/SUP], Yuming Guo[SUP] 3 [/SUP], Pierre Masselot[SUP] 40 [/SUP], Antonio Gasparrini[SUP] 40 [/SUP], Francesco Sera[SUP] 41 [/SUP]
Affiliations
- PMID: 41621133
- DOI: 10.1016/j.envint.2026.110090
Several studies have explored the short-term effects of environmental stressors on coronavirus disease 2019 (COVID-19) transmission and severity. However, evidence on the interactive effects of meteorological conditions and air pollution remains limited and geographically variable. We therefore aimed to quantify the independent and interactive effects of short-term exposure to humidex, a composite index of temperature and relative humidity, and fine particulate matter ≤ 2.5 μm (PM[SUB]2.5[/SUB]) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM[SUB]2.5[/SUB] concentrations were collected from 439 cities in 22 countries during January 2020-August 2022 as part of the Multi-Country Multi-City Collaborative Research Network. A two-stage design was applied: first, city-specific quasi-Poisson models with distributed lag non-linear models estimated exposure-response associations; second, multilevel random-effects meta-analyses pooled city-specific estimates. Effect modification by PM[SUB]2.5[/SUB] was assessed using a product term between non-linear humidex function and linear PM[SUB]2.5[/SUB] function. Approximately 95.1 million confirmed COVID-19 cases were analyzed. Lower humidex values (0.1 °C versus 15.1 °C) were associated with increased daily cases (relative risk [RR]: 1.1192, 95% confidence interval [CI]: 1.0214-1.2262). A 10 μg/m[SUP]3[/SUP]increase in PM[SUB]2.5[/SUB] over the current and preceding 2 days was associated with a modest increase in daily cases (RR: 1.0079, 95% CI: 1.0001-1.0161). No statistically significant interaction between humidex and PM[SUB]2.5[/SUB] was observed. Short-term exposure to cold-dry conditions and elevated PM[SUB]2.5[/SUB] independently increased COVID-19 incidence, highlighting the need to consider both thermal environment and air quality when designing climate-resilient public health responses. These findings enhance understanding of how climate-related environmental stressors influence COVID-19 transmission.
Keywords: COVID-19; Effect modification; Humidex; MCC Collaborative Research Network; PM(2.5); Two-stage design.