2020 · Science of the Total Environment 726, 138605 · Short communication · Single author
1,056 citations on Google Scholar (checked 20 Oct 2026)
Assessing nitrogen dioxide (NO₂) levels as a contributing factor to coronavirus (COVID-19) fatality
The research
I tested whether long-term exposure to nitrogen dioxide helps explain where COVID-19 deaths were concentrated early in the pandemic. The study covered 66 administrative regions in Italy, Spain, France and Germany, with 4,443 deaths reported by 19 March 2020. The purpose of publishing it was to shift attention from pre-existing diseases as the main explanation of mortality towards environmental factors, which deserve further research.
What was novel
- Three datasets in one analysis. Satellite NO₂ (Sentinel-5P TROPOMI, 5.5 km), vertical airflow at 850 hPa and regional death counts were combined at administrative-region level, rather than using national totals.
- Airflow as a dispersal test. Downward airflow keeps NO₂ close to the ground, while upward airflow disperses it. Reading the two together flags regions where high NO₂ is held near the surface.
How the results stand out
Five regions (four in northern Italy and Madrid) account for 3,487 deaths, 78% of the total. They had the highest NO₂ levels, roughly 177–294 µmol/m², and downward airflow. About 83% of deaths fell in regions where NO₂ exceeded 100 µmol/m².
Limitations and the debate
The analysis is descriptive. It has no formal statistical test, no adjustment for age, population density or other confounders, and it uses absolute death counts rather than rates. The “long-term” window is only two months. A commentary by Chudnovsky raised these points, and I responded in follow-up letters in the same journal.
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