UV, ozone, and COVID-19 transmission in Ontario, Canada using generalised linear models

• Published in: Environmental research Vol. 194; p. 110645
• Main Authors: To, Teresa, Zhang, Kimball, Maguire, Bryan, Terebessy, Emilie, Fong, Ivy, Parikh, Supriya, Zhu, Jingqin, Su, Yushan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.03.2021
• Subjects: COVID-19; Humans; Incidence; Linear Models; Ontario; Ontario - epidemiology; Ozone; Ozone - analysis; Reproductive number; SARS-CoV-2; Ultraviolet radiation; Ontario; COVID-19; Ozone; Reproductive number; Ultraviolet radiation; Ontario; Incidence
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2020.110645

Quantifying the impact of environmental factors on COVID-19 transmission is crucial in preventing more cases. Ultraviolet (UV) radiation and ozone (O3) have reported antimicrobial properties but few studies have examined associations with community infectivity of COVID-19. Research suggests UV light can be preventative while the effect of O3 is contested. We sought to determine the relationship between UV, O3, and COVID-19 incidence in Ontario, Canada. In our time series analyses, we calculated daily incidence rates and reproductive number (Rt) from 34,975 cases between January and June 2020 across 34 Ontario Public Health Units. We used generalised linear models, adjusting for potential confounders, to calculate point estimates (PE) and 95% confidence intervals (CI) for UV and O3. Analyses were further stratified by age groups and outbreaks at institutions versus community. We found that 1-week averaged UV was significantly associated with a 13% decrease (95% CI: 0.80–0.96) in overall COVID-19 Rt, per unit increase. A negative association with UV was also significant among community outbreaks (PE: 0.88, 95% CI: 0.81–0.96) but not institutional outbreaks (PE: 0.94, 95% CI: 0.85–1.03). A positive association of O3 with COVID-19 incidence is strongly suggested among institutional outbreak cases (PE: 1.06, 95% CI: 1.00–1.13). Our study found evidence to support the hypothesis that higher UV reduced transmission of COVID-19 and some evidence that ground-level O3 positively influenced COVID-19 transmission. Setting of infection should be strongly considered as a factor in future research. UV and O3 may explain some of COVID-19's seasonal behaviour. •Studied effects of UV and ozone on COVID-19 in Ontario, Canada.•Quantified transmission from 35,000 Ontario COVID-19 cases from January to June 2020.•Higher 1-week lagged UV was associated with decreased COVID-19 transmission.•Higher 1-week lagged O3 was associated with increased COVID-19 transmission.•O3 was a factor for institutional outbreaks while UV was for community outbreaks.