Potential role of particulate matter in the spreading of COVID-19 in Northern Italy: first observational study based on initial epidemic diffusion

  1. Leonardo Setti
  2. Fabrizio Passarini
  3. Gianluigi De Gennaro
  4. Pierluigi Barbieri
  5. Sabina Licen
  6. Maria Grazia Perrone
  7. Andrea Piazzalunga
  8. Massimo Borelli
  9. Jolanda Palmisani
  10. Alessia Di Gilio
  11. Emanuele Rizzo
  12. Annamaria Colao
  13. Prisco Piscitelli
  14. Alessandro Miani

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Abstract

A number of studies have shown that the airborne transmission route could spread some viruses over a distance of 2 meters from an infected person. An epidemic model based only on respiratory droplets and close contact could not fully explain the regional differences in the spread of COVID-19 in Italy. On March 16th 2020, we presented a position paper proposing a research hypothesis concerning the association between higher mortality rates due to COVID-19 observed in Northern Italy and average concentrations of PM 10 exceeding a daily limit of 50 µg/m 3 .

Methods

To monitor the spreading of COVID-19 in Italy from February 24th to March 13th (the date of the Italian lockdown), official daily data for PM 10 levels were collected from all Italian provinces between February 9th and February 29th, taking into account the maximum lag period (14 days) between the infection and diagnosis. In addition to the number of exceedances of the daily limit value of PM 10 , we also considered population data and daily travelling information for each province.

Results

Exceedance of the daily limit value of PM 10 appears to be a significant predictor of infection in univariate analyses (p<0.001). Less polluted provinces had a median of 0.03 infections over 1000 residents, while the most polluted provinces showed a median of 0.26 cases. Thirty-nine out of 41 Northern Italian provinces resulted in the category with the highest PM 10 levels, while 62 out of 66 Southern provinces presented low PM 10 concentrations (p<0.001). In Milan, the average growth rate before the lockdown was significantly higher than in Rome (0.34 vs 0.27 per day, with a doubling time of 2.0 days vs 2.6, respectively), thus suggesting a basic reproductive number R 0 >6.0, comparable with the highest values estimated for China.

Conclusion

A significant association has been found between the geographical distribution of daily PM 10 exceedances and the initial spreading of COVID-19 in the 110 Italian provinces.

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  2. Version published to 10.1136/bmjopen-2020-039338
  3. Version published to 10.1101/2020.04.11.20061713v1 on medRxiv