Low-carbon energy generates public health savings in California

Abstract

Abstract. California's goal to reduce greenhouse gas (GHG) emissions to a level that is 80 % below 1990 levels by the year 2050 will require adoption of low-carbon energy sources across all economic sectors. In addition to reducing GHG emissions, shifting to fuels with lower carbon intensity will change concentrations of short-lived conventional air pollutants, including airborne particles with a diameter of less than 2.5 µm (PM 2.5 ) and ozone (O 3 ). Here we evaluate how business-as-usual (BAU) air pollution and public health in California will be transformed in the year 2050 through the adoption of low-carbon technologies, expanded electrification, and modified activity patterns within a low-carbon energy scenario (GHG-Step). Both the BAU and GHG-Step statewide emission scenarios were constructed using the energy-economic optimization model, CA-TIMES, that calculates the multi-sector energy portfolio that meets projected energy supply and demand at the lowest cost, while also satisfying scenario-specific GHG emissions constraints. Corresponding criteria pollutant emissions for each scenario were then spatially allocated at 4 km resolution to support air quality analysis in different regions of the state. Meteorological inputs for the year 2054 were generated under a Representative Concentration Pathway (RCP) 8.5 future climate. Annual-average PM 2.5 and O 3 concentrations were predicted using the modified emissions and meteorology inputs with a regional chemical transport model. In the final phase of the analysis, mortality (total deaths) and mortality rate (deaths per 100 000) were calculated using established exposure-response relationships from air pollution epidemiology combined with simulated annual-average PM 2.5 and O 3 exposure. Net emissions reductions across all sectors are −36 % for PM 0.1 mass, −3.6 % for PM 2.5 mass, −10.6 % for PM 2.5 elemental carbon, −13.3 % for PM 2.5 organic carbon, −13.7 % for NO x , and −27.5 % for NH 3 . Predicted deaths associated with air pollution in 2050 dropped by 24-26 % in California (1537-2758 avoided deaths yr −1 ) in the "climatefriendly" 2050 GHG-Step scenario, which is equivalent to a 54-56 % reduction in the air pollution mortality rate (deaths per 100 000) relative to 2010 levels. These avoided deaths have an estimated value of USD 11.4-20.4 billion yr −1 based on the present-day value of a statistical life (VSL) equal to USD 7.6 million. The costs for reducing California GHG emissions 80 % below 1990 levels by the year 2050 depend strongly on numerous external factors such as the global price of oil. Best estimates suggest that meeting an intermediate target (40 % reduction in GHG emissions by the year 2030) using a non-optimized scenario would reduce personal income by USD 4.95 billion yr −1 (−0.15 %) and lower overall state gross domestic product by USD 16.1 billion yr −1 (−0.45 %). The public health benefits described here are comparable to these cost estimates, making a compelling argument for the adoption of low-carbon energy in California, with implic...

Effects of Low‐Carbon Energy Adoption on Airborne Particulate Matter Concentrations With Feedbacks to Future Climate Over California

“…The BAU 8 hr max average surface O 3 concentration reaches a maximum of 41.85 ppb in Southern California downwind (east) of LA with increases of 2–4 ppb in northern California and LA under the GHG‐Step scenario. These surface concentration changes are consistent with previous simulations using a stand‐alone regional chemical transport model (Zapata et al, 2018b). Decreasing NO x emissions in the GHG‐Step scenario lead to increasing O 3 concentrations because the BAU scenario had excess NO x that quenched O 3 formation.…”

“…The altered marine emissions increase surface PM 2.5 EC by as much as +0.62 μg m −3 (Figure 2d), surface PM 2.5 sulfate by +0.29 (Figure 2j), surface PM 2.5 OC by +0.13 μg m −3 (Figure 2f), and surface PM 2.5 nitrate by +0.04 μg m −3 (Figure 2h) over the shipping lanes. Increased use of biofuels over land is an economically optimal way to use the limited quantity of biofuels for maximum GHG emissions reductions in the GHG‐Step scenario (Zapata et al, 2018a, 2018b).…”

“…Air quality simulations carried out in past studies predict that the CA‐TIMES GHG‐Step scenario not only reduced GHG emissions but also yielded significantly lower ambient concentrations of criteria pollutants leading to improved public health (Zapata et al, 2018b). The current study focuses on regional forcing by short‐lived pollutants, such as aerosols and ozone (O 3 ).…”

“…The altered marine emissions increase surface PM 2.5 EC by as much as +0.62 μg m −3 (Figure 2d), surface PM 2.5 sulfate by +0.29 (Figure 2j), surface PM 2.5 OC by +0.13 μg m −3 (Figure 2f), and surface PM 2.5 nitrate by +0.04 μg m −3 (Figure 2h) over the shipping lanes. Increased use of biofuels over land is an economically optimal way to use the limited quantity of biofuels for maximum GHG emissions reductions in the GHG-Step scenario (Zapata et al, 2018a(Zapata et al, , 2018b. Surface PM 2.5 nitrate (NO 3 − ) concentrations were predicted to be highest in between Fresno and Bakersfield at 1.11 μg m −3 in the BAU scenario (Figure 2g) with a maximum reduction (−0.39 μg m −3 ) also found at this location when switching to the GHG-Step scenario (Figure 2h).…”

Health Benefits in California of Strengthening the Fine Particulate Matter Standards

“…The avoided all-cause mortality incidence associated with reductions in long-term PM 2.5 exposure was estimated based on pooling log-linear CRF estimated by Jerrett et al and Jerrett et al (California studies), and the kriging and land use regression results are obtained from Krewski et al (US study). While log-linear CRFs were selected for consistency with several recent studies, ,,, it has been suggested that log–log supralinear CRFs (i.e., an upward curving slope) may be more appropriate for estimating mortality incidence at lower PM 2.5 concentrations. , Therefore, avoided mortality incidences are also estimated using the supralinear CRF from Burnett et al (global study) . Relative to the results for log-linear CRFs, 46–57% increases in health benefits are estimated with the increasing difference between supralinear and linear CRF estimations, as the standard is reduced, which agrees with the findings of Marshall et al…”