pm breakdown future for differential effects of...
TRANSCRIPT
PM Breakdown Alternative future science/policy scenarios for
differential effects of particle components
Particulate Matter and Health: Evaluating Alternatives
to a Mass‐Based PM StandardEPRI Air Quality Research Seminar
May 26‐27, 2010Washington, DC
John BachmannVision Air Consulting, LLC
SulfateCarbonaceous
Nitrate
Ammonium
Crustal, metals
Overview
• Today: – Current consensus reflected in EPA Integrated Science
Assessment for indicators for particle pollution, NAAQS
• The future:– Consider alternative futures with improved information on
differential effects of components and the mixture
– Potential regulatory responses to alternative scenarios
Why?
• Recognize tension between NRC, other scientific panel recommendations for multipollutant
approaches and deconstruction of PM
• The Holy Grail: optimized control strategies to maximize risk reductions at minimum costs
• How best to incorporate evolving scientific understandings into policy
PM/Ozone – Multiple pollutants, sources
Pollutants contributing to PM2.5
and OzoneSO2
–
Sulfate particlesNOx
–
Nitrate PM, acid gases, formation of ozone and organic PMVOC
–
formation of ozone and organic PMVOC(C6unsat)
–
secondary organic PMNH3
–
AmmoniumDirect emissions
of carbonaceous PM, crustal materials, metalsCO
–
background ozone formation
Sulfate
Esti Ammonium
Nitrate
Carbonaceous
Crustal
The policy dilemma – split PM, increased focus on integrating multipollutant sources
Multiple sources of multiple pollutants
HNO3
SO2
NO2
CO
Organics
NH3
A brief history of particle pollution • How did we get to standards for a complex mixture?
– From Seneca (61AD) to the New York Times (1940s), Fumus, smoake,
smoke,
soot defined
air pollution
– Source oriented mixture; incomplete combustion
– 1940s‐50s introduced photochemical smog and a focus on gases, specifics
– Ways to measure –
Filter‐based optical (British smoke, Cohs), gravimetric
(TSP) implemented on a routine basis in Europe and the US
– Some interest in measuring chemical components in PM for source
identification and effects assessment (e.g. US NASN)
Gravioris caeli (heavy heaven) in Rome
NY Times 3 Feb 1927
Donora PA 1948
Los Angeles 1943-55
• Community health studies used available monitoring– Focus on differentiating coal smoke particles from related gases
– Toxicology focused high concentrations of a limited number of
laboratory particle types, compounds
– Early criteria used ‘particulates’
for both BS and TSP studies;
presumption all measured generally small combustion aerosols
– PM Criteria led to the first US standards for TSP
A brief history of particle pollution
Legislative Basis for NAAQS• Key issues in criteria (S.108) and NAAQS (S.109)
NAAQS for all pollutants with criteria prior to enactment (includes particulate matter)
List new pollutants and develop criteria Endanger public health or welfareNumerous or diverse mobile or stationary sourceNo existing criteria
Based on the latest scientific criteria….• Primary standards must be requisite
to protect public health
with an
adequate margin of safety*• Secondary standards should protect public welfare (the environment,
materials, visibility, ecosystems….) from known or anticipated adverse
effects• Costs of controlling pollution are not considered
*Legislative history shows Congressional intent to protect a representative sample of the most sensitive groups, not the most sensitive individuals
Anatomy of Air Quality Standards
The four major components of air quality standards– Indicator
‐
i.e. what
is measured (Oxidants, O3
, TSP, PM2.5
) and
how Federal Reference Method (FRM)– Averaging time ‐
1‐hr, 8‐hr, 24‐hr, annual
– Form
‐
statistic – e.g. exceedance, concentration based
– Level
– e.g. 15 ug/m3 (PM), 0.08 ppm O3
(gases)
TSP PM10PM2.5
Evolution of PM NAAQS
• 1971 – EPA promulgates NAAQS for “total suspended
particulate”
(particles smaller than ~25‐45 µm in diameter)
• 1987 – EPA revises PM NAAQS, changing the indicator from TSP
to PM10
to focus on "inhalable" particles (< 10 µm)
• 1997 – EPA revises PM NAAQS to focus separately on the “fine”
and “coarse”
fractions of PM10
– New standards established for “fine”
particles < 2.5 µm in diameter
(PM2.5
)
– PM10
standards retained to focus on “coarse fraction”
(particles
between 2.5 and 10 µm in diameter)
• 2006‐09 – Complete PM NAAQS review/revision– Tighten daily standard, re‐rationalize PM10
– DC Court review: PM10
upheld, remand PM2.5
annual
TSP/PM10 Trends 1960-2005
By 1990; 70 PM10
nonattainment areas
Filter medium change
TSP SIPS on hold during PM NAAQS review
Little progress 1961- 66
Continuous progress 1966-77
Current CAA regulatory authorities in use for PM/components
•
Section 108, 109 Criteria and NAAQS – Lead, TSP, PM10
, PM2.5
– risk based– Indirect – SO2
, NOx
, O3
(VOC) NAAQS– Implementation policy and guidance (multiple authorities) for
State Implementation Plans•
Inventories; monitoring; reasonably achievable control measures
(RACM) ‐
technology (RACT); ‘progress’
requirements; plans to attain
and maintain NAAQS•
Federal measures (e.g.) – Tailpipe standards and regulation of fuels (S, Pb, aromatics, renewables)– Regional transport programs for SOx and NOx (Acid Rain, CAIR)– NSPS, Hazardous air pollutant standards
http://www.epa.gov/air/oaqps/greenbk/7220585.pdf
Direct stationary source authorities
•
Section 111 New Source Performance Standards– NSPS for all “major”
new sources of PM, SOx, NOx, VOC, Pb
i.e. ‘criteria’
pollutants
– 111(d) NSPS for new (federal) and existing (SIP) sources of non‐ criteria pollutants
• Reduced sulfur compounds, fluorides• Sulfuric acid mist; Mercury (remanded)
•
Section 112 Hazardous Air Pollutant Standards– 187 listed HAPs – e.g. Coke oven emissions, POM, As, Cr(IV), Cd,
Mn, Hg, Ni, Pb– PM used to index metals and POM in some rules– Mandated MACT for new and existing major HAP sources;
evaluate residual risk for further controls; e.g. stationary diesels– GACT for smaller sources, urban air toxics program
Other source specific authorities•
Acid rain program – 9.1 mt SOx cap, NOx power plants
•
Title V stationary source permit program•
New source review, PSD increments for PM, gases– Attainment: BACT Nonattainment: LAER + offsets
•
Visibility in 156 class I areas – PM ‘extinction’
weighted•
Mobile sources– Tailpipe standards for new vehicles – Diesel PM, air toxics– Fuels – low S content, reduced aromatics, renewables
Heavy-Duty PM Emissions
What happens in 5‐10 years with significant new scientific
information?Crustal, metals
SulfateCarbonaceous
Nitrate
Ammonium
Science/Policy scenarios• Posit several alternative outcomes based on current
and potential future research programs– Assume ‘reasonably strong’
scientific consensus for each
hypothetical projected outcome regarding components– Variants based on mass, components, sources, interactions– Emphasis on PM2.5
and components
• Consider alternative regulatory responses to scenarios– Examples of how EPA reacted to similar scenarios for TSP,
PM10
, and Pb NAAQS– Indicator(s) and levels for PM NAAQS– Use of NAAQS implementation, source specific authorities
Scientific consensus scenarios•
Current ‐
suggestions of differential toxicity, source
and regional differences, but a multiplicity of signals from multiple sources/components
•
Scenario A*
‐
clear evidence for significantly greater toxicity for a single substance/class – e.g. Ni, UFP in
the mix. 1) Small mass fraction (e.g. Ni)2) Large mass fraction (e.g. primary organics)
•
Scenario B* ‐
clear evidence for significantly greater toxicity for mix of particles from single source class – e.g. diesels, coke ovens
*Assume remainder of mix is lower toxicity, but no additional differentiation possible
Scientific consensus scenarios
•
Scenario C ‐
clear consensus a significant component of PM mass contributes only by influencing the
character of more toxic components
•
e.g. acids mobilizing metals, polymerizing organics
•
‘Inert’
particles as delivery agents for co‐occurring gases
•
Scenario D ‐
clear consensus that a significant mass component is unlikely to play any role in PM effects
•
e.g. sea salt, rural fine dusts
Scientific consensus scenarios
• Scenario E – clear consensus of ability to parse relative harm for multiple components, classes, or sources
1) mix of components makes a significant difference (synergy)
2) whole = sum of the parts
– Information might be limited to major classes of PM – sulfates,
nitrates, primary and secondary carbon, metals, some specifics
– Presumably a worthy research goal, but difficult to achieve
• Insert your own scenario here
Potential Regulatory Responses to Scenarios
Lessons from lead and PM10‐2.5
and PM10
experience
Alternative policy approaches to scenarios A‐E
The past as prologue –
lead (73‐78)
• By 1973, EPA decided against a lead NAAQS in favor of regulation of fuels provision (Scenario A‐1)
• Contested by NRDC in 1976; DC Circuit ruled EPA must list lead under section 108 and develop criteria, NAAQS
(1976)
• First lead NAAQS in 1978; lead continued to be included in TSP/PM10
/PM2.5
mass standards Blood lead in Children
The past as prologue – PM •
PM review 1978‐87– ‘Non‐inhalable’
particles in TSP excluded from PM10
NAAQS
•
PM review (2000‐2006). – Fine particles appeared to dominate effects in many studies,
much less evidence for coarse particles (scenario A‐2)– Still less evidence for rural coarse particles than urban– Regulatory Response:
• Keep PM10
and PM2.5
(final decision, upheld by DC Circuit)• In effect, coarse standard is tighter when fine particles are higher
– Road not taken –
separate coarse NAAQS
•
Recognize constraints and strong inertia in the system –•
regulatory and legal precedents, relative strength of evidence,
consensus ‐
critical in determining nature of regulatory
response.
Scenario A ‐
more toxic componentA‐1 – Minor component of mass
• Retain PM2.5
mass indicator for all components
• Consider nature of source(s) and effects. Evaluate, issue
appropriate standards under source specific provisions of
pollutant/class under 111(d), 112, mobile authorities.
• New NAAQS for minor PM mass component undesirable/unlikely,
but decision to use source specific standards; subject to challenge
A‐2 – Major component of mass• Retain PM2.5
mass indicator for all components
• Adopt additional PM NAAQS for new indicator class.
• Alternatives:– Subtract new indicator mass from PM2.5; adjust levels.
– No new indicator; issue implementation policy and guidance to place
additional priority on sources of A‐2 component
• Implications for levels of remaining undifferentiated PM NAAQS
e.g. Ni
e.g. primary carbonaceous
– Retain PM2.5
mass indicator for all components
– Consider nature of source(s) and effects. • Evaluate, issue appropriate standards under source specific
provisions of pollutant/class under 111(d), 112, mobile authorities
– No new indicator or source specific standards• issue implementation policy and guidance to place additional
priority on named category of PM
– NAAQS for narrow source category appears unlikely
Scenario B – mix of PM from single source category
– Retain PM2.5
mass indicator
– Consider implementation policy and guidance to reduce emphasis on agent or focus on components
enhanced by the component
– Indirect participation in toxicity a rationale for retaining in NAAQS
– Response may depend on the nature and distribution of sources of ‘enhanced’
co‐pollutants
Scenario C –
‘enabling’
component
– Retain PM2.5
mass indicator• Issue implementation policy and guidance to place low
priority on sources of agent (iffy)
• e.g. fugitive dust policy
– Change the indicator exclude non‐contributing material, e.g. PM10 excluded non‐inhalable coarse
particles in TSP• Consider implications for secondary standards (currently
based on visibility), retain original indicator
Scenario D – low toxicity component
Scenario E –
relative toxicity ‘known’ for all major fractions
– Possibly retain a mass standard, strong implementation guidance (more likely if synergy)
– Break PM into a combination of separate NAAQS, and/or technology‐based source specific standards,
implementation guidance
– Level is a function of weighted combination of individual components
• Also an option for multi‐pollutant gas‐particle standards
• Note EPA staff option for secondary PM standard
weights ‘visibility toxicity’
(extinction) by component
Discussion