The effect of short-term exposure to O₃, NO₂, and their combined oxidative potential on mortality in Rome

There is large epidemiological evidence on the short-term health effects of O3 and NO2. These gaseous pollutants induce oxidative stress through their oxidative potential. Therefore, the evaluation of their combined oxidative capacity (Ox) has been proposed rather than studying the effect of either gas individually. To study the short-term effects of daily concentrations of O3, NO2, and Ox on mortality in Rome, in 2002–2015, daily deaths from the city mortality registry were analyzed along with O3 and NO2 levels observed in Rome and with estimated Ox and Owt (Ox, weighted by the redox potential of O3 and NO2). A Poisson regression model was used considering trends, and meteorological and
population changes. The effects on mortality were estimated at lag 0–1 and 0–5 for 10 μg/m3. O3 and NO2 were associated with mortality, with the highest effects at lag 0–5, 0.81% (0.45–1.17) and 2.72% (2.07–3.37), respectively.
Ox had an intermediate effect between the two gases. After adjusting for PM10, Owt had a stronger effect (1.72%; 1.14–2.30) than either gas, 0.86% (0.50–1.22) for O3 and 1.61% (1.15–2.06) for NO2. Both Ox and Owt were associated with
cerebrovascular, respiratory and, to a lesser extent, cardiac mortality more than either gas. These results suggest that the use of Ox (or Owt) can provide a better assessment of the combined role of O3 and NO2 on mortality and can avoid the
uncertainty of the threshold level for ozone. The brain and lungs seem to be the main targets of O3 and NO2.