Final Report: Regional Development, Population Trend, and Technology Change Impacts on Future Air Pollution Emissions in the San Joaquin Valley

EPA Grant Number: R831842
Title: Regional Development, Population Trend, and Technology Change Impacts on Future Air Pollution Emissions in the San Joaquin Valley
Investigators: Kleeman, Michael J. , Handy, Susan , Lund, Jay , Niemeier, Deb
Institution: University of California - Davis
EPA Project Officer: Chung, Serena
Project Period: October 1, 2004 through September 30, 2007 (Extended to September 30, 2010)
Project Amount: $680,000
RFA: Regional Development, Population Trend, and Technology Change Impacts on Future Air Pollution Emissions (2004) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Climate Change , Air


Future base-case emissions inventories were projected for California in the years 2030 and 2050 using projected population growth and existing air pollution regulations as a starting point.  Four unique scenarios that employed different levels of population density were explored for the SJV in the year 2030.  A coupled land use, transportation, area source, and point source emissions model was used to project the emissions for each population density scenario.  The air quality outcomes of all changes to emissions were analyzed using a reactive chemical transport model applied over different spatial and temporal scales. 

Emissions scenarios were also developed for the entire state of California to analyze the co-benefits of energy emissions changes under two different mitigation strategies for climate change.  The measures needed to implement California Assembly Bill (AB) 32 were analyzed for the year 2030 and the scenarios needed to meet the objectives of California Governor’s Executive Order (CGEO) S-3-05 were analyzed for the year 2050.  The air quality outcomes associated with all changes were analyzed using detailed reactive chemical transport models under representative spatial and temporal scales.


Table ES1: Cross comparison of future criteria pollutant emissions inventories created during the current project.

Target Issue

Smart Growth Impact on PM2.5

Global Warming Solutions Act of 2006 (AB32) Impact on PM2.5

California Governor’s Executive Order S-3-05 Impact on PM2.5





Area or Region

San Joaquin Valley

California statewide

California statewide

Population density

Growth only, compact, business as usual, sparse

Business as usual

Business as usual

Land Development

No change, compact, business as usual, sparse

Business as usual

Business as usual

On-road Transportation Sources

No change, compact, as planned, sparse

GHG vehicular standards, efficiency measures, advanced vehicles, drayage truck emission standards

Hydrogen, biofuel, electric, efficient, vehicles, or public mass transit

Other Transportation Sources

High speed rail

Ship electrification, green ships, high speed rail

Farming vehicular, aircraft, farming equipment inc in biofuel scenarios

Electricity and Residential Sources

As planned electrical emissions, landuse based changes for residential

Energy efficiency, renewable, efficient building appliance standards, water related energy consumption reductions

Inc electricity consumption for electric vehicles

Industrial Sources

As planned

Energy efficiency audits to specific manufacturers, refinery and petroleum measures

Increased biorefineries for biofuel scenarios

Agricultural Sources

No change, reduced dairy, reduced dust, increased dairy, increased dust, as planned

Renewable dairy digester biogas energy generation

No change


Future scenarios in the SJV that employ higher population density reduce transportation emissions of criteria pollutants and GHG by an amount up to 20%.  These regional benefits do not necessarily translate into reduced exposure to airborne particulate matter.  Scenarios that specify redevelopment of historical downtown cores with high density housing lead to increased population-weighted concentrations of primary PM components such as elemental carbon and organic compounds.  This trend partly reflects the fact that historical downtown cores in the SJV are located close to major transportation corridors that are dominated by goods-movement rather than commuter trips.  Several levels of emissions controls must be implemented before high density population growth reduces PM exposure relative to low density growth.  Emissions from residential wood combustion must be eliminated, and emissions from food cooking operations and diesel engines must be reduced by 90% before the “as-planned” population density reduces population-weighted PM concentrations relative to a “sparse” density scenario during a simulated severe future air pollution episode.


Figure ES1: Impact of population density (D1=low, D2=medium, D3=high) and emissions control level (C0-C4) on population-weighted PM2.5 concentrations in the SJV. Units are (µg m-3) averaged over the three week study period.

GHG mitigation strategies planned for California will have air quality co-benefits through reduced activity and/or new technologies associated with energy consumption that lead to lower emissions of criteria pollutants.  AB32 measures are predicted to reduce state-wide population-weighted concentrations by ~6% during a future extreme air pollution event.  Projected PM reductions are only 3% in the SJV due to the use of methane capture and combustion units to generate electricity from major dairies.


a) California-wide

b) San Joaquin Valley Air Basin

Figure ES2: Population weighted average percent changes for the 12 day episode, for each AB32 implementation level across the state or air basin. 


The different choices for transportation technology and fuels needed to comply with CGEO S-3-05 also provide co-benefits through reduced criteria pollutant emissions and PM2.5 concentrations.  Two “mixed approach” strategies (Scenarios 6 and 7 in figure ES3) that employ (1) biofuels & hybrid electric vehicles and (2) hydrogen fuel cells & electric vehicles, respectively, both reduce population weighted PM2.5 concentrations by approximately 9% in California during a simulated future wintertime air pollution episode.   Reductions in the SJV are generally similar to those across the entire state due to the uniform application of each strategy across all regions.


a) California-wide
b) San Joaquin Valley Air Basin

Figure ES3: Change in population-weighted PM2.5 concentrations during a 12-day stagnation episode in 2050.  Results are shown for (a) California state-wide average, and (b) SJV average.  The error bars represent the standard deviation due to daily variation in the episode.


Expected Results:

The air quality benefits of “smart growth” community planning, compact building designs with mixed residential / commercial land use in downtown urban cores, must be considered carefully in the SJV.  The proximity of traditional downtown cores next to major transportation corridors for goods movement and other sources that do not scale with population density leads to increased PM exposure under high population density scenarios unless rigorous emissions control programs are implemented simultaneously.  “Smart growth” should not be viewed as a method to reduce public exposure to airborne particulate matter in the SJV.

Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 9 publications 4 publications in selected types All 4 journal articles
Type Citation Project Document Sources
Journal Article Hixson M, Mahmud A, Hu J, Bai S, Niemeier DA, Handy SL, Gao S, Lund JR, Sullivan DC, Kleeman MJ. Influence of regional development policies and clean technology adoption on future air pollution exposure. Atmospheric Environment 2010;44(4):552-562. R831842 (2009)
R831842 (Final)
  • Full-text: Science Direct-Full Text PDF
  • Abstract: Science Direct-Abstract
  • Other: UC Davis-Full Text PDF
  • Journal Article Hixson M, Mahmud A, Hu J, Kleeman MJ. Resolving the interactions between population density and air pollution emissions controls in the San Joaquin Valley, USA. Journal of the Air & Waste Management Association 2012;62(5):566-575. R831842 (Final)
  • Abstract from PubMed
  • Full-text: Taylor and Francis-Full Text PDF
  • Abstract: Taylor and Francis-Abstract
  • Journal Article Kleeman MJ, Zapata C, Stilley J, Hixson M. PM2.5 co-benefits of climate change legislation part 2: California governor's executive order S-3-05 applied to the transportation sector. Climatic Change 2013;117(1-2):399-414. R831842 (Final)
  • Full-text: UC Davis-Full Text PDF
  • Abstract: Springer-Abstract
  • Journal Article Zapata C, Muller N, Kleeman MJ. PM2.5 co-benefits of climate change legislation part 1: California's AB 32. Climatic Change 2013;117(1-2):377-397. R831842 (Final)
  • Full-text: SemanticScholar-Full Text PDF
  • Abstract: Springer-Abstract
  • Supplemental Keywords:

    RFA, Scientific Discipline, Air, climate change, Air Pollution Effects, Environmental Monitoring, Ecological Risk Assessment, Urban and Regional Planning, Atmosphere, ecosystem models, atmospheric carbon dioxide, human activities, VOCs, economic models, emissions impact, greenhouse gases, urban growth, climate models, demographics, ecosystem impacts, air quality, climate variability, Global Climate Change

    Progress and Final Reports:

    Original Abstract
  • 2005 Progress Report
  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report