Damage factors of stratospheric ozone depletion on human health impact with the addition of nitrous oxide as the largest contributor in the 2000s

Abstract

Abstract Purpose Stratospheric ozone (O3) depletion caused by O3-depleting substances (ODSs) remains an unsolved issue. The leakage of older ODSs in the atmosphere continue to affect stratospheric O3, and nitrous oxide (N2O) remains the largest contributor to stratospheric O3 depletion. The purpose of this study was to update the damage factors of stratospheric O3 depletion on human health impacts, particularly skin cancers and eye cataracts, for the years 2010 and 2015 by adding N2O. Methods The framework to derive damage factors followed that of our previous study; the marginal increase in total incidence per unit ODS emission was estimated using the following terms: ground surface emission, tropospheric chlorine loading, equivalent effective stratospheric chlorine (EESC), total O3 in the air column, ultraviolet-B (UV-B) at the ground surface, incidence due to erythemal UV-B exposure, standardized age structure, population, and ODS atmospheric lifetime. By multiplying the disability-adjusted life years (DALYs) per incidence by the marginal increase in total incidence per unit emission, the damage factor was obtained as the DALY per unit emission. The following update was made in this study: the addition of N2O and revisions of the relationship between EESC and total O3, ODS lifetime, population, and DALY per incidence. Results and discussion Damage factors of all ODSs regulated by the Montreal Protocol and of N2O were calculated for melanoma, non-melanoma skin cancers, and eye cataracts. The total damage factors of N2O were 2.1 × 10–5 and 2.2 × 10–5 DALY per kg nitrogen (N) in 2010 and 2015, respectively. These values were smaller than those of chlorofluorocarbons and halons; however, the global effect of N2O on stratospheric O3 depletion was approximately 170,000 DALYs or 3.9 billion USD in 2010, accounting for 48% of the total damage. The damage factor of N2O on climate change was estimated, based on existing literature, to be 27 times higher than that for stratospheric O3 depletion estimated in this study. Conclusions N2O is currently the largest contributor to stratospheric O3 depletion, which accounted for approximately 50% of the total health impact induced by all ODSs in 2010. Although another important impact of N2O, i.e., climate change, was demonstrated to be 27 times more damaging than stratospheric O3 depletion, this means that N2O emissions contribute to two global environmental issues simultaneously. Thus, efforts to reduce N2O emissions should be increased.