The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities

Keita Wagatsuma; Denise Feurer; Wenhua Yu; Rongbin Xu; Tim Riffe; Maxi Stella Kniffka; Enrique Acosta; Ben Armstrong; Malcolm Mistry; Rachel Lowe; Dominic Royé; Masahiro Hashizume; Aurelio Tobias; Ana Maria Vicedo-Cabrera; Lina Madaniyazi; Chris Fook Sheng Ng; Carmen Íñiguez; Martina S. Ragettli; Eric Lavigne; Patricia Matus Correa; Nicolás Valdés Ortega; Jan Kyselý; Aleš Urban; Hans Orru; Ene Indermitte; Marek Maasikmets; Susanne Breitner-Busch; Alexandra Schneider; Yasushi Honda; Barrak Alahmad; Antonella Zanobetti; Joel Schwartz; Gabriela Carrasco; Iulian Horia Holobâca; Ho Kim; Whanhee Lee; Michelle L. Bell; Noah Scovronick; Fiorella Acquaotta; Micheline de Sousa Zanotti Stagliorio Coelho; Magali Hurtado Diaz; Eunice Elizabeth Félix Arellano; Paola Michelozzi; Massimo Stafoggia; Francesca de’Donato; Shilpa Rao; Xerxes Seposo; Shilu Tong; Jochem Klompmaker; Yuming Guo; Pierre Masselot; Antonio Gasparrini; Francesco Sera

doi:10.1016/j.envint.2026.110090

The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities

Keita Wagatsuma^*
, Denise Feurer
, Wenhua Yu
, Rongbin Xu
, Tim Riffe
, Maxi Stella Kniffka
, Enrique Acosta
, Ben Armstrong
, Malcolm Mistry
, Rachel Lowe
, Dominic Royé
, Masahiro Hashizume
, Aurelio Tobias
, Ana Maria Vicedo-Cabrera
, Lina Madaniyazi
, Chris Fook Sheng Ng
, Carmen Íñiguez
, Martina S. Ragettli
, Eric Lavigne
, Patricia Matus Correa

Nicolás Valdés Ortega, Jan Kyselý, Aleš Urban, Hans Orru, Ene Indermitte, Marek Maasikmets, Susanne Breitner-Busch, Alexandra Schneider, Yasushi Honda, Barrak Alahmad, Antonella Zanobetti, Joel Schwartz, Gabriela Carrasco, Iulian Horia Holobâca, Ho Kim, Whanhee Lee, Michelle L. Bell, Noah Scovronick, Fiorella Acquaotta, Micheline de Sousa Zanotti Stagliorio Coelho, Magali Hurtado Diaz, Eunice Elizabeth Félix Arellano, Paola Michelozzi, Massimo Stafoggia, Francesca de’Donato, Shilpa Rao, Xerxes Seposo, Shilu Tong, Jochem Klompmaker, Yuming Guo, Pierre Masselot, Antonio Gasparrini, Francesco Sera

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

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_2.5) 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_2.5 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_2.5 was assessed using a product term between non-linear humidex function and linear PM_2.5 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/m³ increase in PM_2.5 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_2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM_2.5 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.

Original language	English
Article number	110090
Pages (from-to)	110090
Journal	Environment international
Volume	208
DOIs	https://doi.org/10.1016/j.envint.2026.110090
State	Published - Feb 2026

Bibliographical note

Publisher Copyright:
© 2026 The Author(s).

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being
SDG 11 Sustainable Cities and Communities

Keywords

COVID-19
Effect modification
Humidex
MCC Collaborative Research Network
PM
Two-stage design

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10.1016/j.envint.2026.110090

Cite this

Wagatsuma, K., Feurer, D., Yu, W., Xu, R., Riffe, T., Kniffka, M. S., Acosta, E., Armstrong, B., Mistry, M., Lowe, R., Royé, D., Hashizume, M., Tobias, A., Vicedo-Cabrera, A. M., Madaniyazi, L., Sheng Ng, C. F., Íñiguez, C., Ragettli, M. S., Lavigne, E., ... Sera, F. (2026). The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities. Environment international, 208, 110090. Article 110090. https://doi.org/10.1016/j.envint.2026.110090

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title = "The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities",

abstract = "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 (PM2.5) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM2.5 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 PM2.5 was assessed using a product term between non-linear humidex function and linear PM2.5 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/m3 increase in PM2.5 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 PM2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM2.5 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, Two-stage design",

author = "Keita Wagatsuma and Denise Feurer and Wenhua Yu and Rongbin Xu and Tim Riffe and Kniffka, \{Maxi Stella\} and Enrique Acosta and Ben Armstrong and Malcolm Mistry and Rachel Lowe and Dominic Roy{\'e} and Masahiro Hashizume and Aurelio Tobias and Vicedo-Cabrera, \{Ana Maria\} and Lina Madaniyazi and \{Sheng Ng\}, \{Chris Fook\} and Carmen {\'I}{\~n}iguez and Ragettli, \{Martina S.\} and Eric Lavigne and Correa, \{Patricia Matus\} and Ortega, \{Nicol{\'a}s Vald{\'e}s\} and Jan Kysel{\'y} and Ale{\v s} Urban and Hans Orru and Ene Indermitte and Marek Maasikmets and Susanne Breitner-Busch and Alexandra Schneider and Yasushi Honda and Barrak Alahmad and Antonella Zanobetti and Joel Schwartz and Gabriela Carrasco and Holob{\^a}ca, \{Iulian Horia\} and Ho Kim and Whanhee Lee and Bell, \{Michelle L.\} and Noah Scovronick and Fiorella Acquaotta and \{de Sousa Zanotti Stagliorio Coelho\}, Micheline and Diaz, \{Magali Hurtado\} and \{F{\'e}lix Arellano\}, \{Eunice Elizabeth\} and Paola Michelozzi and Massimo Stafoggia and Francesca de{\textquoteright}Donato and Shilpa Rao and Xerxes Seposo and Shilu Tong and Jochem Klompmaker and Yuming Guo and Pierre Masselot and Antonio Gasparrini and Francesco Sera",

note = "Publisher Copyright: {\textcopyright} 2026 The Author(s).",

year = "2026",

month = feb,

doi = "10.1016/j.envint.2026.110090",

language = "English",

volume = "208",

pages = "110090",

journal = "Environment international",

issn = "0160-4120",

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Wagatsuma, K, Feurer, D, Yu, W, Xu, R, Riffe, T, Kniffka, MS, Acosta, E, Armstrong, B, Mistry, M, Lowe, R, Royé, D, Hashizume, M, Tobias, A, Vicedo-Cabrera, AM, Madaniyazi, L, Sheng Ng, CF, Íñiguez, C, Ragettli, MS, Lavigne, E, Correa, PM, Ortega, NV, Kyselý, J, Urban, A, Orru, H, Indermitte, E, Maasikmets, M, Breitner-Busch, S, Schneider, A, Honda, Y, Alahmad, B, Zanobetti, A, Schwartz, J, Carrasco, G, Holobâca, IH, Kim, H, Lee, W, Bell, ML, Scovronick, N, Acquaotta, F, de Sousa Zanotti Stagliorio Coelho, M, Diaz, MH, Félix Arellano, EE, Michelozzi, P, Stafoggia, M, de’Donato, F, Rao, S, Seposo, X, Tong, S, Klompmaker, J, Guo, Y, Masselot, P, Gasparrini, A & Sera, F 2026, 'The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities', Environment international, vol. 208, 110090, pp. 110090. https://doi.org/10.1016/j.envint.2026.110090

TY - JOUR

T1 - The joint impact of temperature, humidity, and air pollution on COVID-19 incidence

T2 - a multi-country time-series study in 439 cities

AU - Wagatsuma, Keita

AU - Feurer, Denise

AU - Yu, Wenhua

AU - Xu, Rongbin

AU - Riffe, Tim

AU - Kniffka, Maxi Stella

AU - Acosta, Enrique

AU - Armstrong, Ben

AU - Mistry, Malcolm

AU - Lowe, Rachel

AU - Royé, Dominic

AU - Hashizume, Masahiro

AU - Tobias, Aurelio

AU - Vicedo-Cabrera, Ana Maria

AU - Madaniyazi, Lina

AU - Sheng Ng, Chris Fook

AU - Íñiguez, Carmen

AU - Ragettli, Martina S.

AU - Lavigne, Eric

AU - Correa, Patricia Matus

AU - Ortega, Nicolás Valdés

AU - Kyselý, Jan

AU - Urban, Aleš

AU - Orru, Hans

AU - Indermitte, Ene

AU - Maasikmets, Marek

AU - Breitner-Busch, Susanne

AU - Schneider, Alexandra

AU - Honda, Yasushi

AU - Alahmad, Barrak

AU - Zanobetti, Antonella

AU - Schwartz, Joel

AU - Carrasco, Gabriela

AU - Holobâca, Iulian Horia

AU - Kim, Ho

AU - Lee, Whanhee

AU - Bell, Michelle L.

AU - Scovronick, Noah

AU - Acquaotta, Fiorella

AU - de Sousa Zanotti Stagliorio Coelho, Micheline

AU - Diaz, Magali Hurtado

AU - Félix Arellano, Eunice Elizabeth

AU - Michelozzi, Paola

AU - Stafoggia, Massimo

AU - de’Donato, Francesca

AU - Rao, Shilpa

AU - Seposo, Xerxes

AU - Tong, Shilu

AU - Klompmaker, Jochem

AU - Guo, Yuming

AU - Masselot, Pierre

AU - Gasparrini, Antonio

AU - Sera, Francesco

PY - 2026/2

Y1 - 2026/2

N2 - 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 (PM2.5) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM2.5 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 PM2.5 was assessed using a product term between non-linear humidex function and linear PM2.5 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/m3 increase in PM2.5 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 PM2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM2.5 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.

AB - 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 (PM2.5) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM2.5 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 PM2.5 was assessed using a product term between non-linear humidex function and linear PM2.5 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/m3 increase in PM2.5 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 PM2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM2.5 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.

KW - COVID-19

KW - Effect modification

KW - Humidex

KW - MCC Collaborative Research Network

KW - PM

KW - Two-stage design

UR - https://www.scopus.com/pages/publications/105029027309

U2 - 10.1016/j.envint.2026.110090

DO - 10.1016/j.envint.2026.110090

M3 - Article

C2 - 41621133

AN - SCOPUS:105029027309

SN - 0160-4120

VL - 208

SP - 110090

JO - Environment international

JF - Environment international

M1 - 110090

ER -

The joint impact of temperature, humidity, and air pollution on COVID-19 incidence: a multi-country time-series study in 439 cities

Abstract

Bibliographical note

UN SDGs

Keywords

Access to Document

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