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IUAPPA-IPURGAP Reducing the Impact of Vehicles On Air and Environmental Quality in Cities January 22-23, 2004 The Mexico City Air Quality Case Study Mario J. Molina and Luisa T. Molina Massachusetts Institute of Technology Topographical Map of the MCMA Population Growth

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Reducing the Impact of Vehicles

On Air and Environmental Quality in Cities

January 22-23, 2004

The Mexico City Air Quality Case Study

Mario J. Molina and Luisa T. Molina

Massachusetts Institute of Technology


Topographical Map of the MCMA

  • Population Growth
    • 17.5 million (1999): 20-fold increase since 1900
    • Growth projection to 25 million (2010)
  • Urban Sprawl
    • 1500 km2 (1999): 10-fold increase since 1960
    • Expansion to peripheral areas
  • Geographic and Topographical Conditions
    • High altitude (2240m): less efficient combustion processes
    • Mountains are a physical barrier for winds
    • 2nd largest mega-city in the world
    • Temperature inversions in the dry season
  • Increases in Emissions Sources

Trends in criteria pollutant concentrations for the MCMA

(averages of data at five RAMA sites: TLA, XAL, MER, PED, and CES)


Trends in criteria pollutant concentrations for the MCMA

(averages of data at five RAMA sites: TLA, XAL, MER, PED, and CES)


Integrated Program on Urban, Regional and Global Air Pollution: Mexico City Case Study (Mexico City Air Quality Program)


Provide objective, balanced assessments of the causes and alternative cost-effective solutions to urban, regional and global air pollution problems through quality scientific, technological, social and economic analysis in the face of incomplete data and uncertainty

- Use Mexico City as the initial case study

- Develop an approach that applies globally

- Build on strong base of ongoing basic research


Collaborative Research and Education Program

Mexican Participants

Universidad Autónoma Metropolitana (UAM)

Instituto Mexicano del Petróleo (IMP)

Petroleos Mexicanos (PEMEX)

Universidad Nacional Autónoma de México (UNAM)

Universidad de las Americas, Puebla (UDLA)

Universidad Iberoamericana (UIA)

Instituto Tecnológico de Estudios Superiores de Monterrey (ITESM)

Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT)

Instituto Nacional de Ecología (INE); Centro Nacional de Investigación y Capacitación Ambiental (CENICA)

Gobierno del Distrito Federal (GDF); Secretaria de Medio Ambiente (SMA)

Gobierno del Estado de México, Secretaria de Ecología (SEGEM)

Secretaría de Salud (SS)

Insituto Nacional de Salud Pública (INSP)

US Participants

Massachusetts Institute of Technology (MIT)Washington State University (WSU)

Montana State University (MSU)

University of Colorado at Boulder (UC)

Lawrence Berkeley National Laboratory (LBNL)

Aerodyne Research Inc. (ARI)

Department of Energy/Atmospheric Science Program (DOE/ASP)

Argonne National Laboratory (ANL)

Pacific Northwest National Laboratory (PNNL)

Los Alamos National Laboratory (LANL)

Colorado State University (CSU)

Pennsylvania State University (PSU)

National Science Foundation (NSF)

University of California at Riverside (UCR)

National Center for Atmospheric Research (NCAR)

European Participants

Chalmers University, Sweden

ETH-ZurichEcole Polytechnique Federal de Lausanne

University of Heidelberg

Free University of Berlin


Summary of the First Phase of the

Mexico City Air Quality Program

Chapter 1. Air Quality Impacts: A Global and Local Concerns

Chapter 2. Cleaning the Air: A Comparative Overview

Chapter 3. Forces Driving Pollutant Emissions in the MCMA

Chapter 4. Health Benefits of Air Pollution Control

Chapter 5. Air Pollution Science in the MCMA: Understanding Source-Receptor Relationships Through Emissions Inventories, Measurements and Modeling

Chapter 6. The MCMA Transportation System: Mobility and Air Pollution

Chapter 7. Key Findings and Recommendations

Estimates of mortality impacts from particulate matter, drawn from time-series studies worldwide and in Mexico City

Estimated Health Benefits of a 10% Reduction of Pollution Levels in the MCMA

Background Rate

Risk Coefficient

Risk Reduction




(% per 10µg/m3)






Time Series








10 000


Risk Coefficient

Background Rate

Risk Reduction


(% per 10µg/m3)



Time Series





Minor Restricted




Activity Days


Focus of the Second Phase of the

  • Mexico City Air Quality Program
  • Systematic development of scientific information, evaluation methodologies and simulation tools in the following areas:
  • activities that lead to the generation of pollutants in the MCMA (transportation, production of goods and services, degradation of the natural environment, etc.);
  • dispersion and transformation of atmospheric pollutants (focus on ozone and particles);
  • evaluation of risks and the effects of pollutants on the population;
  • cost-benefit analysis of control strategies;
  • integrated assessment of policy options and priorities for control strategies;
  • strategies for capacity building.

MCMA-2003 Field Measurement Campaign

Science Questions

  • Emission inventories:
  • What are the sources of NH3? HCHO? What are their emissions rates?
  • Are hydrocarbon emissions underestimated? Are NOx emissions overestimated?
  • Are there significant biogenic emissions, e.g., terpenes?
  • Chemistry: transformation of emissions in the atmosphere
  • How is the reduction in NOx and/or HC related to reduction in O3 and PM?
  • Would reductions in NOx lead to a reduction in nitrate particulates?
  • What is the impact of reducing ammonia?
  • How much HCHO is primary vs. secondary (produced photochemically)?
  • What is the partitioning of NOy (NOx, HNO3, organic nitrates)?
  • What are the sources and the chemical composition of the fine PM?

MCMA-2003 Field Measurement Campaign

Science Questions (cont)

  • Meteorology:
  • What is the height of the mixing layer?
  • How does it evolve with time?
  • Is there any “carry over” of pollutants from one day to the next?
  • Do the models satisfactorily predict wind speeds and directions?
  • Urban-Regional-Global Chemical Transformation:
  • What are the effective source terms for emissions for global climate models?
  • What are the roles of aerosols in modifying the local/regional radiative transfer processes and cloud properties?

Ozone with 1-4 x HC emissions

Mar. 2, 1997

Mar. 14, 1997

Ozone concentrations are average of all measurement sites.


MCMA-2003 Field Campaign

Supersite Instrumentation

Supersite Location: CENICA (UAM-Ixtapalapa)

  • Instrumentation:
  • CENICA - monitoring station, tethered balloon
  • RAMA - monitoring station
  • WSU – VOC sampling
  • DOE/ PNNL – PTRMS, single particle sampler/analyzer, MFRSBR, RSR
  • UCB/LBL – Particle sampling apparatus
  • DOE/Argonne National Lab – PAN, black carbon, olefins, NH3
  • Colorado U. – AMS
  • Penn State – OH and HO2
  • IMP – MINIVOLS and MOUDI , aldehyde cartridges
  • MIT/U. Heidelberg - DOAS
  • MIT/ Free U. Berlin – LIDAR
  • MIT – PAHs
  • UCR – nitro-PAHs, PAHs
  • Chalmers – FTIR, DOAS
  • Plus others
mit iup doas equipment on cenica roof top hut
MIT/IUP DOAS equipment on Cenica Roof-top (Hut)
  • DOAS-1
  • L= 960m
  • H= 16m
  • BTX, Styrene
  • Benzaldehyde, Phenol
  • Naphtalene
  • NO2, HONO
  • HCHO, O3, SO2
  • DOAS-2
  • L= 4420m
  • H= 70m
  • HONO, HCHO, O3
  • NO2, (NO3)
  • SO2
  • Glyoxal
  • Radiation:
  • Spectrometry
  • Actinic photon flux
  • (incl. straylight)
  • -> any J-value
  • Filterradiometry
  • J(NO2)

East South South-West

aerosol mass spectrometer ams at cenica
Aerosol Mass Spectrometer (AMS) at CENICA
  • 100% transmission (60-600 nm), aerodynamic sizing, linear mass signal.
  • Jayne et al., Aerosol Science and Technology 33:1-2(49-70), 2000.
  • Jimenez et al., J. Geophys. Res.- Atmospheres, 108(D7), 8425, doi:10.1029/ 2001JD001213, 2003.

Mobile Laboratory Modes of Operation

February 2002

Stationary Sampling

High time resolution point sampling

Quality Assurance for conventional

air monitoring sites

Mobile Sampling/Mapping

Motor vehicle pollution emission ratios

Large source plume identification

Ambient background pollution distributions


Detailed mobile source

emissions characterization

Plume tracer flux measurements


Environmental Education and Outreach

  • Visiting Mexican scholars at MIT
  • Workshops/symposia on air quality
  • Professional development courses on air quality for mid-career personnel in the government, industry and academic sectors as well as non-governmental organizations and the media
  • Masters Program in Environment and Health Management at MIT and Harvard School of Public Health (INE-MIT-Harvard joint program)
  • Exchange program between MIT and Mexican institutions
  • Establish the Research and Development Network on Air Quality in Large Cities in Mexico
  • Web-based activities for senior high school teachers and students (with Monterrey Tech, ITESM)

MIT Scenario Analysis

  • Integrating Bottom-Up and top-Down Analytic Approaches
  • Three Feasibility “Screens”
    • Technical Feasibility (effective)
    • Economic Feasibility (affordable)
      • Pursued through quantitative analysis
    • Political Feasibility (implementable)
      • Pursued through qualitative dialogue
  • “Feasibility” depends in part upon the “Future Story”
      • Allows us to identify more robust options

A Diverse Mix of Emissions/Sources

Source: CAM 1998 MCMA Emissions Inventory

collaborative activities with latin american cities
Collaborative Activities with Latin American Cities

Air quality forecasting training workshops (with Santiago de Chile and São Paulo)

Transportation/land use and atmospheric modeling and measurements (with Santiago de Chile and other Latin American cities)

Inter-American Network for Atmosphere and Biosphere Studies (IANABIS)


Fleet composition and operations

  • Provide incentives to increase the turnover rate of the trucks, taxis, colectivos, and private auto fleets.
  • Enforce existing regulations on maximum age of taxis and colectivos
  • Develop incentives to encourage retrofitting of trucks with emission control devices.
  • Continue audits of Vehicle Verification Testing Stations using on-road test data, and correct irregularities

Public transportation

  • Give priority to the organization of the transportation system
  • at the metropolitan level, including the improvement and
  • coordination of all the current modes of transport.
  • Increase the use of the metro system by improving service
  • quality, performance, and personal security.
  • Facilitate inter-modal transfers to improve convenience and
  • speed of public transport.
  • Important origins and strategic destinations should be
  • considered in the planning for the proposed expansion of the
  • metro network.


  • Develop infrastructure to enable intercity truck traffic to bypass the downtown core in order to improve air quality and reduce congestion.
  • Evaluate the feasibility of implementing Intelligent
  • Transportation Systems (ITS) to improve traffic management
  • and thereby reducing pollution.
  • Consider alternative transportation pricing policies, enabled
  • by ITS, to reduce the volume of traffic and pollution.


  • Establish new specifications with lower sulfur content in
  • gasoline and diesel that enable the introduction of future
  • cleaner vehicle technologies.
  • Develop natural gas as a potential transportation fuel for
  • urban buses and intra-urban trucks
  • Prohibit illegal vehicle conversions to run on LPG without
  • adequate emission controls

Recommendations (short term)

  • Improve enforcement
    • Taxis < 6 years old (DF), <10 years old (EM).
    • Microbuses <7 years old
    • Registration and license plates.
    • Centralize VVP database.
    • VVP certificates up to date/not counterfeit.
    • Increase audits & evaluations of VVP.
    • Traffic regulations.
  • Improve Data
    • Establish reliable registration database.
    • Improve trip data.
    • Update traffic accounting data.
    • Use remote sensing and tunnel tests to improve emission inventory.
    • Make emission and vehicle data publicly available for new and used vehicles.

Recommendations (medium term)

  • Control Vehicle Demand
    • Limit private vehicle use.
    • Restrict taxi numbers through a permitting process.
    • Regulate colectivo’s, but encourage their continuation.
    • Create ‘no private vehicle’ areas in DF.
    • Discourage single passenger trips.
  • Upgrade the Fleet
    • Registration fees less age sensitive.
    • Tighten VVP emission standards for older vehicles and inspect trucks (NOx, PM, PAH)
    • Require vehicle retrofit (gasoline and diesel).
    • Upgrade bus fleet.
    • Acquire USA standards at only two year delay.
    • Lower sulfur (gasoline and diesel).

Recommendations (long term)

  • Land Use Planning
    • Establish a regional planning commission with authorities & financial independence like SCAQMD.
    • Generate a long term plan that is consistent with high mobility and low pollution.
    • Enforce sanctity of land reserves.
    • Develop and use a mobility/land use tool for planning.
  • Public Transport
    • Integrate colectivos with public transport.
    • Promote multi-mode transport fares.
    • Encourage park & ride.
    • Improve security and safety on public transport and in park & ride lots.
    • Give traffic preference to public transport and multi-person vehicles (dedicated lanes, etc.)