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

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. [ABSTRACT FROM AUTHOR]