Wildfire Dominates the PM2.5 Budget
California’s PM2.5 comes overwhelmingly from wildfire smoke. On-road transport is 11%. Residential sources are 1.2%. Power generation is 0.1%. The entire controllable fraction — everything electrification can touch — is only 12.3% of total PM2.5 exposure.
Policy attention goes to the 12% that can be electrified. The question here is what happens if a fraction of that attention goes to the 77% instead.
Wildfire Treatment vs Transport Electrification
We compare wildfire PM2.5 reduction scenarios against the transport and building electrification policies at 2035. Transport and building deaths are net — after the regional ozone chemistry (LA-Basin disbenefit, Central Valley benefit) is accounted for. Wildfire has no ozone interaction. We report both CRFs: Di (conservative) and Krewski (higher risk per µg/m³).
| Intervention | Deaths (Di) | Deaths (Krewski) | Cost ($B) | $/Death (Di) |
|---|---|---|---|---|
| T1 Baseline (ACC II) | 455 | 1,450 | $0 | Free |
| T2 Accelerated | 626 | 2,001 | $2.0B | $3.20M |
| 5% Wildfire Reduction | 330 | 1,099 | $0.8–2.5B | $2.5–7.5M |
| 10% Wildfire Reduction | 661 | 2,196 | $1.7–5.0B | $2.5–7.5M |
| 20% Wildfire Reduction | 1,172 | 3,857 | $3.3–9.9B | $2.82–8.45M |
| B2 Accelerated (Building) | 57 | 180 | $2.0B | $34.9M |
Di deaths come from the point-estimate ozone-PM2.5 integration. Krewski-CRF deaths scale by the Krewski/Di ratio (~3.2) observed in the Monte Carlo. Wildfire cost range: $500–$1,500/acre across 1.65–9.9M acres annually. Transport cost from CEC scenario definitions. Under Di, wildfire 10% (661 deaths) edges ahead of Transport T2 (626); under Krewski, wildfire dominates. See Inv 08 for the CRF burden-scale analysis — Di and Krewski agree on T2 as the optimal transport scenario, but the age-threshold difference rescales the burden ~4×.
Wildfire Dominates Every Region
The wildfire share is not just a statewide average. In every major air basin, wildfire PM2.5 exceeds on-road transport by at least 6:1. Sacramento is the most extreme: wildfire is 90% of PM2.5 while on-road is just 6%.
| Region | Wildfire % | On-Road % | Wildfire / On-Road |
|---|---|---|---|
| LA Basin | 74% | 12% | 6:1 |
| San Joaquin Valley | 75% | 14% | 6:1 |
| Bay Area | 87% | 6% | 14:1 |
| Sacramento | 90% | 6% | 15:1 |
| Rest of CA | 81% | 11% | 8:1 |
This is not an argument against electrification. T1 baseline (ACC II) is free and avoids 455 deaths (Di); it should proceed regardless. The question is where the marginal $2B goes. Wildfire treatment is now a co-leading candidate, and choosing between it and transport turns on which CRF you trust. See Inv 08 (CRF Policy Flip).
Di et al. 2017 CRF · CARB emissions inventory · InMAP source-receptor matrix · Census tract population · Wildfire PM2.5 from MODIS/GlobFire · Prescribed burn cost literature ($33–100/acre) · Linear scaling (conservative)