&EPA
www.epa.gov/airscience
science in ACTION
CLEAN AIR RESEARCH
PROGRAM
NEW MODELS BEING DEVELOPED TO ESTIMATE EFFECTS OF PARTICULATE
MATTER AT DIFFERENT DOSES
Issue:
Why are some people's lungs
more affected by the same level
of air pollutants than others?
How does it impact them
differently? What is the
relationship between a particular
exposure condition and the
amount of pollutant that they
inhale?
Research that examines the
"dose" received from an air
pollutant is bridging the gap
between measurable air pollutants
and known health outcomes such
as pulmonary disease. It also
contributes to an understanding of
why people may respond
differently to the same air
pollutants.
The dose to the lung can vary
widely among individuals
depending on genetics, age, sex,
health status, and lifestyle.
For example, a dose of particulate
matter (PM) inhaled into certain
regions within the lung's airways
can be many times more harmful
in individuals with obstructive
airway disease than in healthy
individuals. Therefore, the
susceptibility of an individual to a
dose needs to be better
understood.
In addition, PM is a complex
mixture of different sized
particles and chemical
compounds. Thus, the lungs can
be impacted in different ways
depending on how much of a PM
type is deposited and where the
deposition occurs.
The knowledge gained from the
study of dose (or dosimetry
research) can be used to evaluate
risks to individuals and
susceptible groups and assist the
U.S. Environmental Protection
Agency in establishing effective
air pollution regulations.
Science Objective:
The Clean Air Research Program
in EPA's Office of Research and
Development addresses key
questions about PM dosimetry,
including the following:
• What host and PM-specific
factors determine the dose and
distribution in the lung?
• How best can the internal dose
be measured and characterized?
• Who experiences greater
internal dose from exposure
and thus is at greater risk?
• How can we accurately
estimate or predict internal dose
from daily exposures to PM?
EPA researchers have developed
a new method of measuring
continued on back
U.S. Environmental Protection Agency
Office of Research and Development
-------
&EPA
www.epa.gov/airscience
science in ACTION
CLEAN AIR RESEARCH PROGRAM
continued f-omjront
deposition of PM in the lung and
have applied this method to
characterize lung dose in various
groups, including young and
older adults, and individuals with
obstructive lung disease (e.g.,
asthma and chronic bronchitis).
These data are being used to
develop a simple, empirical
"lung-deposition model."
Although practical, most
dosimetry models are designed
for only healthy adults and simple
exposure conditions. Therefore,
EPA investigators are also
developing a comprehensive and
more versatile mathematical
model to apply to the variety of
real-world exposure conditions.
The model must be customizable
to estimate dose for people of
varying personal lifestyles, health
status, and places of residence.
Such a model will be valuable for
analyzing various exposure
scenarios taking place in the real
world and identifying the kinds of
exposure conditions under which
people are subjected to high lung
dose and thus high risk of harm
from exposure to PM.
Application and Impact:
EPA scientists have made
significant advances in the
development of models to
improve our understanding of the
relationship between exposure to
PM and the amount of dose
received in the lung. Findings
include:
• PM lung dose is determined
primarily by particle size and
how people breathe (e.g., slow,
fast, shallow, deep). Slow and
deep breathing or exercise can
increase lung deposition.
• Within the lung, not all regions
receive the same dose. Certain
lung regions are subject to
much greater dose than others.
Therefore, these high-dose
regions may be more
vulnerable to PM effects.
• Nano (ultrafine) PM deposits in
almost the same regions of the
lung as do coarse, micron-size
particles. Thus, very small and
large PM may exert a
compounded impact to those
regions where they deposit.
• Generally, PM dose is
comparable between healthy
young and older people in both
men and women, but regional
(hotspot) doses can be greater
in individuals with obstructive
lung disease.
ORD's research on PM dosimetry
helps to address the health risks
of PM by informing air pollution
standards and public health
advisories.
REFERENCES
Kim CS and Jaques PA. Analysis of total
respiratory deposition of inhaled ultrafine particles
in adult subjects at various breathing patterns.
Aerosol Sci. Technol. 38:525-540, 2004.
Kim CS. and Hu SC. Total respiratory tract
deposition of micrometer-sized particles in healthy
adults: Empirical equations for sex and breathing
pattern. J. Applied Physiol. 101:401-412, 2006.
Choi, J. and Kim, C. S. Mathematical analysis of
particle deposition in human lungs: An improved
single-path transport model. Inhalation Toxicol.
19:925-939, 2007.
CONTACT
Chong S. Kim, Ph.D., National Health and
Environmental Effects Research Laboratory,
EPA's Office of Research and Development, 919-
966-5049, kim.chong@epa.gov.
MARCH 2009
U.S. Environmental Protection Agency
Office of Research and Development
------- |