Ground-level ozone
The UNECE/WHO Task Force on Health recommended the use of the SOMO35 as a relevant ozone indicator for health impact assessments (UNECE/WHO 2003). SOMO35 is calculated as the sum over the year of the daily 8-h maximum ozone concentrations in excess of a 35 ppb threshold. Based on a comprehensive meta-analysis of time series studies conducted for the World Health Organization [4] and on advices received from the UNECE/ WHO Task Force on Health, the GAINS model quantifies premature mortality through an association with the SOMO35 indicator. Contrary to \(PM_{2.5}\) GAINS`_ does not quantify the loss of life expectancy or Years of Life Lost from exposure to ground-level ozone but only mortality impacts.
The GAINS calculation estimates the full-year daily changes in mortality as a function of daily 8-h maximum ozone concentrations, employing the concentration-response curves derived in the above-mentioned meta-analysis. The annual cases of premature mortality attributable to ozone in receptor region k are then calculated as follows:
where:
\(d_{BL}(k)\) |
Natural-cause baseline annual total deaths in region k |
SOMO35(k) |
Population-weighted mean SOMO35 exposure in region k expressed in \(\mu g ^{-3}.d\) |
\(\beta_{O_3}\) |
Risk coefficient corresponding to changes in relative risk for 1 \(\mu g ^{-3}.d\) increase in exposure |
Note that, in GAINS v4.0.3, the relative risk devised by Orellano et al. [9] has been implemented and will be updated pending advice from the World Health Organization in the upcoming HRAPIE2 assessment.