Commentary on the Critical Review
Public Health and Components of Particulate
Matter: The Changing Assessment of Black Carbon
Michael T. Kleinman
Department of Medicine
University of California, Irvine
Recent Findings and Implications of Air QualityRelated Health Research at UC Irvine
• Nearly 50% of deaths are
associated with heart disease.
• Biomarkers of heart disease are
associated with organic (OC) and
elemental carbon (EC)
components of UFP.
• EC may be important because
large surface area may act as a
“carrier” that brings chemicals into
areas that they couldn’t ordinarily
reach.
• EC and BC are possible surrogates
for motor vehicle emissions and
may also be causally related to CV
morbidity and mortality.
• Near road exposures promote
airway allergies;
• PM exposure accelerates
atherosclerosis.
• PM exposure is associated with
inflammation and oxidative stress
in the brain.
When we studied the effects of
ultrafine particles on airway allergies,
• The association with
allergy biomarkers e.g.
IL-5 was:
– strongest for elemental
carbon (EC) and organic
carbon constituents
(OC).
– not explained by
differences in particle
number, metals or
particle mass
concentrations
Testing the Roles of Black and Organic Carbon
• Human biomarker study (Delfino) indicated importance of UFP organic carbon (OC)
constituents related to coronary artery disease.
• We had previously shown that UFP accelerates atherosclerosis in mice.
• We had also shown that PM is less reactive, in vitro, when we remove the organic
constituents from UFP using a denuder (which works analogously to modern diesel
afterburner emission controls).
• So we tested the hypothesis that removal of the OC from UFP would block the
acceleration of atherosclerosis.
Ambient Air
Electrostatic
Classifier
315 lpm
Electrostatic
Classifier
CPC
15 lpm
5 lpm
CPC
Diffusion Dryer
0.3 lpm
Virtual Impactor
10 lpm
Condenser
300 lpm
Ultrafine
Impactor
(Dp 50 =180 nm
Saturation Tank
VACES
Pump
Adsorption
/Cooling
2.5 lpm
4.7 lpm Quartz f ilter
4.7 lpm
5 lpm
2.5 lpm
Heater
Heater
Quartz f ilter
Thermodenuder
Tef lon f ilter
Tef lon f ilter
Pump
1. We exposed mice in LA to air,
denuded and undenuded PM.
2. We examined serum biomarkers
and arteries
Black Carbon and Brown Carbon?
• Black carbon (BC) is a major component of “soot”, a
complex light-absorbing mixture that comprised of a
mixture of Elemental Carbon (EC) and Particulate
Organic Carbon (OC).
• BC is the most strongly light-absorbing component of
particulate matter (PM), and is formed by the
incomplete combustion of fossil fuels, biofuels, and
biomass.
• BC is emitted directly into the atmosphere in the form
of fine particles (PM2.5) and ultrafine particles (PM0.1).
These are also considered nanoparticles.
• BC is the most effective form of PM, by mass, at
absorbing solar energy: per unit of mass in the
atmosphere, BC can absorb a million times more
energy than carbon dioxide (CO2).
• Organic carbon aerosols are a significant absorber of
solar radiation. The absorbing part of organic aerosols
is referred to as "brown" carbon (BrC).
EC
OC +
BrC
BC
http://www.epa.gov/blackcarbon/basic.html
Changes in Particle Composition After
Thermal Denuding
Health-related characteristics of Ultrafine PM
-3
dM/dlog10 dva (µg m )
12
ultrafines
less oxygenated
(to denuder)
quasiultrafines
10
m/z 55 (C4H7
+)
4
2
m/z 44 (CO2+)
0
2
3
4
5 6 7 8 9
100
 0.4
1000
m/z 55 (C4H7
When you denude the UFP
3500
Ambient
Denuded
2.0
1.5
2
+)
dva (nm)
47 %
42 %
66 %
1.0
0.5
Concentraton, pg/m3
DTT activity, nmol/min/m3
2.5
larger particles
oxygenated
6
3.5
3.0
Organics
Sulfate
Ammonium
Nitrate
8
5 6 7 8 9
m/z 44 (CO2+)
accumulation mode
3000
2500
Ambient
HMW PAHs
Denuded
14%
2000
53 %
1500
1000
81 %
500
0
0.0
50 C
100 C
Temperature
200 C
50 C
100 C
Temperature, oC
200 C
4
Removing the Organic Constituents
From Ambient UFP Blocks CV Effects
Reflections on CR Conclusions
• Conclusion: ‘Using the U.S. EPA rubric for judging causality, we
conclude that there is a causal relationship between BC/EC for all
cause and various CVD mortality and morbidity endpoints.”
– The OC may be more associated with disease causality than the EC
– If true different mitigation approaches may be necessary to best protect public
health.
• Conclusion: “…in rapidly developing countries having high levels
of air pollution, it is clear that concentrations of BC and PAHs are
considerably higher than in the US and Western Europe, and that
adverse health outcomes are also highly elevated in these
countries. “
– The potential causal role of toxic organic components of combustion
emissions suggests that future consideration of more specific metrics of
air quality as opposed to “bulk” metrics such as particle mass or particle
number may be needed as part of a clean air strategy.