IMPROVING EXPOSURE DATA INPUTS
Needed to Assess Environmental Risks of Older Adults
Kent Thomas1, NicolleTulve\Tom McCurdy1, Miles Okino1, Ron Williams1, and Lisa Melnyk2
U.S. EPA/Office of Research and Development, National Exposure Research Laboratory, 'Human Exposure and Atmospheric Sciences Division
and Microbiological and Chemical Exposure Assessment Research Division
Aging Initiative Background
A goal of the US EPA's Aging Initiative is the development of a coordinated
program to address the environmental health concerns and risks that
may confront the nation's rapidly expanding population of older adults. To
address health issues, the Office of Research and Development (ORD)
Laboratories and Centers are working together to apply the environmental
public health paradigm to better understand the relationships between
external pollution sources, human exposures, internal doses, early
biological effects, and adverse health effects for older adults.
In addition to considering the health effects of exposures on healthy older
adults, EPA will use information about aging-related changes in activity,
exposure, and pharmacokinetic and pharmacodynamic factors to identify
particularly vulnerable subgroups within this diverse population.
It is important to understand the range of older adults' physical activities,
activity patterns, and residential locations to understand their potential
exposures to environmental contaminants. Those experiencing both higher
exposures and increased biological susceptibility may be at elevated risk for
adverse health outcomes.
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Figure 1. The Environmental Public Health Paradigm
and ORD Labs and Centers
Science Issues
There are many uncertainties that must be addressed in the areas of exposure and activity
assessment in order to better understand potential risks to environmental stressors in the
aging population. These include:
> Which chemical and biological stressors have been associated with impaired health in older
populations?
> What is the range of exposures to these stressors for older adults?
> Do exposures to chemical and biological stressors change (increase or decrease) with aging?
> How do aging-related changes in lifestyle, physical activity, activity patterns, locations,
pharmaceutical use, and diets affect exposures and pharmacokinetic processes?
> What groups of older persons are more susceptible to risks from environmental exposures?
What do we know about exposures and activities for these groups?
Figure 2- Susceptibility and the Public Health Paradigm
Figure 3. Activity, Exposure, and Susceptibility
Impact of Research for
Aging Populations
> Research on older adults' activities, exposures, and their subsequent pharmacokinetic
responses will reduce uncertainties in risk assessment through understanding and
elucidating the fundamental determinants of exposure and dose.
> This work will compile and consolidate existing data for use in exposure-to-dose and
pharmacokinetic models applicable to aging populations, and will provide additional aging-
specific information for the EPA's Exposure Factors Handbook.
> The information will be used by risk managers and risk assessors who need to incorporate
the differential susceptibility of this heterogeneous group into decisions affecting risk and
public health.
Aging-Related Research in the National Exposure Research Laboratory
Exposure
Assessment
> An outcome-based literature review is being performed to identity chemical and
biological stressors that may pose health risks for older adults.
> Information is being compiled on exposures to environmental contaminants for older
adults from literature sources and extant databases such as the National Health and
Nutrition Examination Survey and the National Human Exposure Assessment Survey.
> Panel studies of exposures experienced by older adults to particulate matter (PM)
have been completed in several regions of the country. Longitudinal data were
collected for exposures, exposure factors, and activity patterns.
Location
Mean
Age
%
Retired
% Time
Indoors
% Time
Outdoors
% Time
Other
Mean (Range)
Plv^g Personal
Exposure ((ig/m3)
Baltimore
81
96
94
4
2
13 (6.8-25)
Fresno 1
82
100
-
13 (0.4-24)
Fresno II
82
100
-91
-8
<1
11 (7.2-16)
RTP 1
64
86
84
4
12
28 (7.8-86)
RTPII
67
92
85
7
8
22 (8.3-100)
Figure 4. Example of Information from Selected PM Panel Studies
Exposure and Dose Modeling
> Aging-related changes in physiological parameters will be applied in physiologically
based pharmacokinetic models such as the Exposure Related Dose Estimating
Model (ERDEM).
> Sensitivity and uncertainty analysis of modified models will be performed to deter-
mine key parameters and identify data gaps where more information is needed to
reduce model uncertainties for older adults.
Work in the National Exposure Research
Laboratory is directed toward characterizing
what is known about activity, exposure, and dose for
environmental stressors at different life stages in the
aging population and to identifying key data gaps.
Completed and ongoing research is described in
several areas.
Activity Patterns and
Physical Activity
> Age-specific information will be compiled for physical activity, activity pattern,
location and microenvironment, and physiology from extant literature and databases
such as the Consolidated Human Activity Database (CHAD).
> These activity and physiological data will be analyzed to understand and identify
important differences in the aging population and to determine the adequacy of
existing data, particularly with regard to longitudinal patterns and for susceptible
sub-populations.
> Results will be organized to support human exposure and pharmacokinetic
modeling and for inclusion in an older adult Exposure Factor Handbook.
Figure 5. Conceptual Framework for Aging Activity and
Physiological Relationships
Identifying Susceptible Sub-populations
> It is important to develop information on activities and exposures for subgroups of the aging population that may be more vulnerable to environmental
hazards. However, age-based groupings alone are not sufficient for identifying groups that may be more highly exposed due to their locations or
activities or more susceptible due to their health status.
> Research will be performed to identify potentially vulnerable sub-populations and what is known about their health, activities, diets, and pharmaceutical
use that might increase risk. Critical data gaps can then be identified in important sub-populations for future research activities.
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