Review of the Primary National Ambient Air Quality Standard for Sulfur Oxides

117 Pages·2017·2.86 MB·English

by  Hagan, Nicole

Review of the Primary National
Ambient Air Quality Standard for
Sulfur Oxides:
Risk and Exposure Assessment
Planning Document
[This page intentionally left blank.]
EPA-452/P-17-001
February 2017

Review of the Primary National Ambient Air Quality
Standard for Sulfur Oxides:
Risk and Exposure Assessment Planning Document

U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Office of Air and Radiation
Health and Environmental Impacts Division
Research Triangle Park, North Carolina
DISCLAIMER

This document has been prepared by staff in the Health and Environmental Impacts
Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency
(EPA). Any findings and conclusions are those of the authors and do not necessarily reflect the
views of the Agency. This document is being circulated to facilitate discussion with the Clean
Air Scientific Advisory Committee and for public comment to inform the EPA’s consideration of
the primary national ambient air quality standard for sulfur oxides. This information is
distributed for the purposes of pre-dissemination peer review under applicable information
quality guidelines. It does not represent and should not be construed to represent any Agency
determination or policy.
Questions or comments related to this document should be addressed to Dr. Stephen
Graham, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
C539-07, Research Triangle Park, North Carolina 27711 (email: [email protected]) and
Dr. Nicole Hagan, U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, C504-06, Research Triangle Park, North Carolina 27711 (email:
[email protected]).

i
TABLE OF CONTENTS
LIST OF FIGURES ...................................................................................................................... v
LIST OF TABLES ....................................................................................................................... vi
LIST OF ACRONYMS AND ABBREVIATIONS .................................................................. vii
EXECUTIVE SUMMARY .................................................................................................... ES-1
1 INTRODUCTION .............................................................................................................. 1-1
1.1 Background ................................................................................................................. 1-2
1.2 Conceptual Model for SO Exposure and Risk ........................................................... 1-3
2
REFERENCES ......................................................................................................................... 1-7
2 OVERVIEW OF THE PREVIOUS ASSESSMENT ...................................................... 2-1
2.1 Analysis Approach and Modeling Elements ............................................................... 2-1
2.1.1 Additional Analyses of Monitoring Data ............................................................... 2-3
2.1.2 Air Quality Scenarios ............................................................................................. 2-3
2.1.3 Benchmark Levels, Exposure-Response, and Risk Metrics .................................. 2-4
2.1.4 Relationship Between 1-Hour and 5-Minute Concentrations ................................ 2-6
2.2 Air Quality-Based Assessment ................................................................................... 2-6
2.2.1 Air Concentrations ................................................................................................. 2-7
2.2.2 Study Areas and Years ........................................................................................... 2-9
2.2.3 Comparison of Air Concentrations to Benchmarks ............................................... 2-9
2.2.4 Key Uncertainties and Limitations ...................................................................... 2-10
2.3 Risk and Exposure Assessment ................................................................................. 2-12
2.3.1 Study Areas, Time Period, and Simulated Population ......................................... 2-12
2.3.2 Exposure Modeling .............................................................................................. 2-13
2.3.2.1 Air Concentrations ........................................................................................... 2-15
2.3.2.2 Simulated Populations ...................................................................................... 2-16
2.3.2.3 Human Activity Patterns .................................................................................. 2-17
2.3.2.4 Microenvironmental Concentrations ................................................................ 2-18
2.3.2.5 Exposure Estimates .......................................................................................... 2-18
2.3.3 Health Risk Characterization ............................................................................... 2-19
2.3.4 Key Uncertainties and Limitations ...................................................................... 2-20
REFERENCES ....................................................................................................................... 2-24
3 CONSIDERATION OF THE NEWLY AVAILABLE INFORMATION .................... 3-1
ii
3.1 Key Considerations ..................................................................................................... 3-1
3.2 Health Effects Information .......................................................................................... 3-2
3.2.1 At-Risk Populations ............................................................................................... 3-3
3.2.2 Lung Function Decrements .................................................................................... 3-3
3.2.3 Other Endpoints ..................................................................................................... 3-4
3.3 Ambient Air Concentrations ....................................................................................... 3-5
3.3.1 Estimation of 5-Minute Concentrations ................................................................. 3-5
3.3.2 Characterizing the Spatial and Temporal Distribution of 1-hour SO Concentrations
2
................................................................................................................................ 3-7
3.4 Exposure Estimates ..................................................................................................... 3-7
3.4.1 Microenvironmental Concentrations ..................................................................... 3-8
3.4.2 Human Activity Patterns ........................................................................................ 3-8
3.4.3 Physical Attributes and Ventilation Rate ............................................................... 3-9
3.4.4 Exposure Estimate Bins ....................................................................................... 3-10
3.5 Conclusions ............................................................................................................... 3-10
REFERENCES ....................................................................................................................... 3-13
4 PLAN FOR THE CURRENT HEALTH RISK AND EXPOSURE ASSESSMENT ... 4-1
4.1 Population-based Exposure Assessment ..................................................................... 4-2
4.1.1 APEX Model Overview ......................................................................................... 4-3
4.1.2 Exposure Domain................................................................................................... 4-4
4.1.2.1 Study Areas and Time Periods ........................................................................... 4-4
4.1.3 SO Concentrations in Ambient Air ..................................................................... 4-12
2
4.1.3.1 Monitor Data Completeness Requirements...................................................... 4-12
4.1.3.2 Approach for Estimating Missing Values in Ambient Air Monitor Data ........ 4-13
4.1.3.3 AERMOD Predicted Concentrations ............................................................... 4-17
4.1.3.4 Adjusting Concentrations to Just Meet a Standard .......................................... 4-19
4.1.4 Microenvironmental Concentrations ................................................................... 4-22
4.1.5 At-Risk Populations ............................................................................................. 4-24
4.1.6 Simulated Individuals .......................................................................................... 4-24
4.1.6.1 Population Demographic Information .............................................................. 4-25
4.1.6.2 Asthma Prevalence ........................................................................................... 4-25
4.1.6.3 Commuting ....................................................................................................... 4-27
4.1.6.4 Human Activity Patterns .................................................................................. 4-27
iii
4.1.6.5 Personal Attributes ........................................................................................... 4-29
4.1.7 Exposure Assessment Estimates .......................................................................... 4-30
4.2 Health Risk Characterization .................................................................................... 4-31
4.2.1 Health Endpoints .................................................................................................. 4-31
4.2.2 Target Ventilation Rates ...................................................................................... 4-31
4.2.3 Exposure Benchmark-Based Health Risk ............................................................ 4-32
4.2.3.1 Benchmark Levels ............................................................................................ 4-32
4.2.3.2 Exposure Benchmark-based Risk Results ........................................................ 4-33
4.2.4 Lung Function Decrement-based Health Risk ..................................................... 4-34
4.2.4.1 Development of Exposure-Response Functions .............................................. 4-34
4.2.4.2 Lung Function Decrement-based Health Risk Results .................................... 4-39
4.3 Assessment of Variability and Characterization of Uncertainty ............................... 4-40
4.3.1 Assessment of Variability and Co-variability ...................................................... 4-41
4.3.2 Characterization of Uncertainty ........................................................................... 4-41
REFERENCES ....................................................................................................................... 4-44

LIST OF APPENDICES
A. Consideration of Support in Newly Available Information for Quantitative Assessment of
Other Asthma-Related Health Outcomes
B. Occurrences of 5-Minute SO Concentrations of Interest in the Recent Ambient Air
2
Monitoring Data (2013-2015)
C. Comparisons of SO Hourly Concentration Distributions between High and Low Years in
2
2011-2015
iv
LIST OF FIGURES
Figure 1-1. Conceptual model for exposure and associated health risk of SO in ambient air. .. 1-6
2
Figure 2-1. Overview of analysis approach for 2009 REA. Blue boxes indicate approach for
estimating air concentrations, purple boxes indicate exposure modeling, and red
dashed boxes indicate use of health effects information. ......................................... 2-3
Figure 3-1. Trend in number of monitors with 5-minute data. .................................................... 3-6
Figure 4-1. Overview of the analysis approach for the REA. ..................................................... 4-2
Figure 4-2. Map indicating approximate dimensions of potential model-based study area (blue
circles surrounding sources) and SO emission sources > 100 tons per year in Brown
2
County, WI. .............................................................................................................. 4-8
Figure 4-3. Map indicating approximate dimensions of potential model-based study area (blue
circles surrounding sources) and SO emission sources > 100 tons per year in
2
Cuyahoga County, OH. ............................................................................................. 4-9
Figure 4-4. Map indicating approximate dimensions of potential model-based study area (blue
circles surrounding sources) and SO emission sources > 100 tons per year in
2
Hillsborough County, FL. ....................................................................................... 4-10
Figure 4-5. Map indicating approximate dimensions of a potential model-based study area (blue
circles surrounding sources) and SO emission sources > 100 tons per year in Marion
2
County, IN. ............................................................................................................. 4-11
Figure 4-6. Comparison of low and high concentration years using recent data (2011-2015) for
daily maximum 1-hour SO concentrations in ambient air in Hillsborough County,
2
FL (top left), Cuyahoga County, OH (top right), and Marion County, IN (bottom
left), and Brown County, WI (bottom right)........................................................... 4-21
Figure 4-7. Percent of individuals experiencing changes in sRaw ≥ 100% using controlled
human exposure study data (Table 4-6) fit using a probit regression (solid line).
Annotated with the number of study subjects from each study, dashed line indicates a
5th and 95th percentile prediction interval for the mean. Models for SO exposures
2
from 200-1,000 ppb (top panel) and for SO exposures from 200-600 ppb (bottom
2
panel). ..................................................................................................................... 4-38

v
LIST OF TABLES
Table 2-1. Air quality scenarios evaluated in the 2009 REA. .................................................... 2-4
Table 2-2. Adjustment approach for each air quality scenario in the 2009 REA. ..................... 2-8
Table 4-1. Candidate study areas that meet the air quality, design value, and population criteria.
............................................................................................................................ 4-7
Table 4-2. Descriptive statistics for evaluating the approach used to substitute missing 1-hour
and 5-minute maximum concentrations using a monitor in Cuyahoga County, OH
(ID 390350038): all available measurements (no substitution) and that supplemented
with data where missing values were present. ........................................................ 4-14
Table 4-3. Example of estimated continuous 5-minute concentrations for hours for which only
the maximum 5-minute and 1-hour average concentrations are known and using
equation 4-1 or equation 4-2. .................................................................................. 4-16
Table 4-4. Example of estimated continuous 5-minute concentrations for hours for which more
than one 5-minute concentration and the 1-hour average concentration are known
and using equation 4-3. ........................................................................................... 4-17
Table 4-5. Estimated asthma prevalence for children and adults in four potential study areas. .....
.......................................................................................................................... 4-27
Table 4-6. Summary of controlled human exposure studies containing individual response data:
number and percent of individuals who experienced greater than or equal to a 100 or
200 percent increase in specific airway resistance (sRaw), adjusted for effects of
exercise in clean air. ............................................................................................... 4-37
Table 4-7. Estimated percent of the population experiencing sRaw ≥ 100% considered at 5 ppb
increments and using two different data sets to derive the E-R function: one using all
SO exposures, the other using only SO exposures between 200-600 ppb. .......... 4-39
2 2

vi
LIST OF ACRONYMS AND ABBREVIATIONS

APEX Air Pollutants Exposure model
AQS Air Quality System
BSA body surface area
CAA Clean Air Act
CASAC Clean Air Scientific Advisory Committee
CHAD Consolidated Human Activity Database
EGU Electricity generating unit
EPA Environmental Protection Agency
EVR equivalent ventilation rate
FEV forced expiratory volume in one minute
1
FR Federal Register
IRP Integrated Review Plan
ISA Integrated Science Assessment
ME microenvironment
MET metabolic equivalent of task
MSA metropolitan statistical area
NAAQS National Ambient Air Quality Standard
NEI National Emissions Inventory
NHANES National Health and Nutrition Examination Survey
NHIS National Health Interview Survey
NO nitrogen dioxide
2
O ozone
3
OAQPS Office of Air Quality Planning and Standards
ppb parts per billion
PA Policy Assessment
PM particulate matter
PMR peak-to-mean ratio
PRB policy-relevant background
REA Risk and Exposure Assessment
RMR resting metabolic rate
SO sulfur dioxide
2
SO oxides of sulfur
X
sRaw specific airway resistance
V̇ activity-specific ventilation rate
E
vii