Mobile Source Air Toxics

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Mobile Source Air Toxics

• Richard Cook
• Office of Transportation and Air Quality

Air Toxics Center Assessment and Standards
Division Phone [phone] e-mail
cook.rich_at_epa,gov
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Mobile Source Air Toxics

• More than 700 compounds have been identified in
  exhaust and evaporative emissions from onroad and
  nonroad mobile sources
• 21 of these compounds were listed in recent
  mobile source air toxic rulemaking (202(l)(2)) as
  hazardous air pollutants.
• Compounds list in IRIS (EPA Integrated Risk
  Information Database) as known, probable, or
  possible human carcinogens, or have RfC or RfD
  for chronic non-cancer effects.
• We are currently re-evaluating this list

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List of Mobile Source Air Toxics
Found in evaporative as well as exhaust
emissions.
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What is the mobile source contribution to the air
toxics problem?
Sum of 188 Emissions (Million tons) in
1999 Major 1.3 Area and Other 1.6 Mobile
Onroad 1.4 Mobile Nonroad 0.8
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What is the mobile source contribution to the air
toxics problem?
Mobile sources account for about half of total
risk (does not include diesel PM)
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Mobile Source Air Toxics of Greatest Concern

• Diesel Exhaust
• Likely human carcinogen at environmental exposure
  levels
• Too many uncertainties to derive a unit risk
• Low end of occupational exposures and
  environmental exposures overlap
• Range of environmental risk in U.S. potentially
  10-3 to 10-5
• Diesel PM also contributes significantly to the
  effects (premature mortality) associated with
  fine PM
• Gasoline PM -- an emerging issue

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Mobile Source Air Toxics of Greatest Concern

• Benzene
• Known human carcinogen, causes leukemia
• Chronic exposure is also associated with a number
  of other blood disorders
• recent research shows effects at exposure levels
  below 5 ppm
• Lifetime cancer risk from exposure to benzene
  from ambient sources exceeds 1 in 100,000
  (1x10-5) for more than half the U.S. population
  (1996 National Air Toxics Assessment)
• About 75 of emissions are from mobile sources

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Mobile Source Air Toxics of Greatest Concern

• 1,3-Butadiene
• U.S. EPA recently released new risk assessment
• Known human carcinogen
• Causes a variety of reproductive and
  developmental effects in mice and rats
• Results of 1996 NATA suggest upper bound lifetime
  cancer risk from exposure to 1,3-butadiene from
  ambient sources exceeds 1 in 1 million (1x10-6)
  for more than half the U.S. population
• About 60 of emissions from mobile sources

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Mobile Source Air Toxics of Greatest Concern

• Formaldehyde
• U.S. EPA currently working on revised risk
  assessment
• Currently considered likely human carcinogen,
  causes nasal tumors in rats
• Recently published research by National Cancer
  Institutes shows causal relationship in humans
  between formaldehyde exposure and cancer of the
  nasopharynx
• Also a respiratory irritant
• About half of emissions from mobile sources

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Mobile Source Air Toxics of Greatest Concern

• Acetaldehyde
• U.S. EPA currently working on revised risk
  assessment
• Currently considered likely human carcinogen,
  causes nasal tumors in rats
• Also a respiratory irritant
• Results of 1996 NATA suggest upper bound lifetime
  cancer risk from exposure to acetaldehyde from
  ambient sources exceeds 1 in 1 million (1x10-6)
  for more than half the U.S. population
• About 70 of emissions from mobile sources

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Mobile Source Air Toxics of Greatest Concern

• Acrolein
• U.S. EPA recently completed a revised risk
  assessment
• respiratory tract irritant
• Exposures to acrolein exceed RfC for noncancer
  effects (respiratory) for almost the entire U.S.
  population
• About 40 of emissions from mobile sources

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How are existing programs impacting mobile source
air toxics?

• Many programs are reducing air toxics
• Highway vehicles
• Tier 2 vehicle and gasoline sulfur standards,
  2007 heavy duty rule, Phase 2 Reformulated
  Gasoline, mobile source air toxic
  anti-backsliding standards
• Nonroad
• Tier 4 nonroad rule, recreational vehicle rule,
  small spark ignition engine controls, locomotive
  and commercial marine diesel rules

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How are existing programs impacting mobile source
air toxics?

• Nonroad equipment
• HAP emissions reduced from 860K tons in 1996 to
  560K tons in 2020
• Highway vehicles
• Reduction in emissions between 1996 and 2020 over
  2 million tons, from about 2.5 million to 0.5
  millions tons, or 83
• Emissions may increase slightly between 2020 and
  2030

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New Regulatory Initiatives
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Community-based Programs

• Reduce air toxics in short term
• New standards dont address existing fleet
• Slow fleet turnover for trucks, nonroad equip.
• Local, voluntary strategies
• Retrofits (trucks, buses, nonroad equipment)
• Low-sulfur diesel fuel
• Anti-idling
• Commuter Choice (travel demand management)

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OTAQ Air Toxics Research

• Designed to address the following questions
• What do we know about ambient concentrations?
• What do we know about elevated concentrations in
  hotspots ?
• e.g., near roadways and from attached garages?
• What do we know about personal and occupational
  exposure levels?
• What are the implications for estimating risk?

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OTAQ Air Toxics Research

• Emissions Research
• Diesel nonroad emissions testing
• Done at Southwest Research
• Final reports to be released this summer
• Small engine emission test program (OTAQ/NERL)
• currently underway
• Motor vehicle mercury emissions test program
  (OTAQ/NERL)
• pilot program at U of Mich
• Next phase in planning process

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OTAQ Air Toxics Research

• Air Quality and Exposure Modeling
• Local-scale air modeling
• with OAQPS/EPA Regions/States and locals
• improving our ability to capture spatial
  gradients and high end exposure
• Houston, Portland, Philadelphia
• Use link level highway vehicle inventories
• Air quality and exposure modeling for future
  years using NATA tools
• with OAQPS

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OTAQ Air Toxics Research

• Monitoring hotspots and personal exposure
• Providing support for studies addressing near
  roadway microenvironment in Baltimore and Fresno
• Supported ARB/UC study of exposure in school
  buses
• Supporting analysis of data from RIOPA Study
• How do mobile sources and attached garages
  contribute to personal exposure

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Emission Inventory Improvement

• National Mobile Inventory Model (NMIM)
• creates national, county-level emission
  inventories
• criteria pollutants, gaseous HAPs, PAHs, metals
• includes MOBILE6.2, NONROAD, county database in a
  JAVA framework
• streamlines inventory development process and
  makes it easier for States to provide improved
  local inputs
• National Emissions Inventory
• Final 1999 mobile source inventory using latest
  tools and methods
• Draft 2002 inventory
• Revised 1990 and 1996 inventories consistent with
  1999 and 2002
• http//www.epa.gov/ttn/chief/net/
• Projected inventories to 2030 being developed.

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Additional Information

• Kathryn Sargeant
• Director, Air Toxics Center
• 734-214-4441
• sargeant.kathryn_at_epa.gov
• Chris Lieske
• Team Leader, mobile source air toxics rule
• 734-214-4584
• lieske.christopher_at_epa.gov
• Website
• www.epa.gov/otaq/toxics.htm