Estimating human health damage factors related to CO2 emissions by considering updated climate-related relative risks

Abstract

Frequent updates on the evaluation of health risks associated with climate change are made. The existing health damage factors associated with CO2 emission are based on the findings compiled by the 2004 World Health Organization (WHO) report. An updated version of the 2014 WHO report is now available, and based on its contents, this study aimed to estimate relative risk (RR) and calculate health damage factors for each shared socioeconomic pathway (SSP) scenario. Damage factors (DALY/kg-CO2) were calculated as increment of temperature (°C/kg) multiplied by increment of RR per °C, base mortality rate without climate change (−), population, and disability-adjusted life year (DALY) per case of death. RRs and base mortality rates were calculated for each SSP scenario. RRs by SSP scenario were estimated based on the RRs of three economic growth scenarios (high growth, base case, and low growth), which were calculated based on the results of the 2014 WHO report. Base mortality rates for each SSP scenario were calculated based on its relationship with gross domestic product per capita. In relation to undernutrition, diarrhea, malaria, dengue, heat stress, and coastal floods, the health damage factors (DALY/kg) for the SSP1, SSP2, and SSP3 scenarios were 1.3 × 10−6, 1.5 × 10−6, and 2.0 × 10−6, respectively. During a 100-year evaluation period, the damage factors obtained in the current study were 3–5 times higher than those in previous studies mainly because relative risk per degree Celsius (RR/°C) in the 2014 WHO report was larger than that in the 2004 WHO report. When RRs were estimated for each SSP scenario, the RR of SSP3 (with higher base mortality) was relatively low, particularly in case of undernutrition. Therefore, differences in the damage factors between the scenarios were more likely smaller than before when a single RR was used. New health damage factors for the SSP1, SSP2, and SSP3 scenarios were estimated using an updated RR calculated based on the 2014 WHO report. These factors can be further updated in the future using RRs obtained from upcoming researches on climate-related health impact that were based on SSP scenarios.