ATSDR-Particulate-Matter-Guidance-508.pdf

PM Guidance for ATSDR Health Assessment Products June 2024 update

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Guidance for Inhalation Exposures to Particulate Matter

Citation:

[ATSDR] Agency for Toxic Substances and Disease Registry. 2024. Guidance for Inhalation

Exposures to Particulate Matter. Atlanta, GA: U.S. Department of Health and Human Services,

Public Health Service, June 2024

Contents

1. Introduction

1.1. Background

1.2. Purpose

2. Public Health Evaluation Approach for Particulate Data 4

2.1. Pre-evaluation 4

2.2. Process for Assessing PM Data 6

2.2.1. Step 1: Data Averaging 7

2.2.2. Step 2: PM Screening 7

2.2.2.1. Special consideration: Short-term exposure studies of ≤24-hour exposures 9

2.2.3. Step 3: Data Evaluation 11

2.2.3.1. Acute exposures 11

2.2.3.2. Chronic exposures 13

3. Integrating steps 1-3 and adding cautionary statements 13

3.1. Scenario 1: The appropriately averaged data are consistently below AQGs 13

3.2. Scenario 2: The appropriately averaged data are above AQGs: 14

3.3. Example language 15

Appendix A: Particulate Matter National Data Summaries from the U.S. EPA Air Quality System (AQS) 17

Appendix B: U.S. Environmental Protection Agency Particulate Matter AQI designations and Health

Statements* 25

4. References 15

PM Guidance for ATSDR Health Assessment Products June 2024 update

1. Introduction

1.1. Background

Particulate matter (PM) is the generic term for a broad class of chemically and physically

diverse solid particles and liquid droplets found in the ambient air (Figure 1). Particles originate

from a variety of anthropogenic sources, both stationary (e.g., coal-fired power plants) and

mobile (e.g., cars and trucks), as well as from natural (e.g., dust storms) sources. In addition to

being directly emitted into the air, particles can be formed in the atmosphere through complex

reactions involving chemicals such as sulfur dioxide (SO

) and nitrogen dioxide (NO

). PM is a

mixture of various components (e.g., metals, elemental carbon (EC), organic compounds (OC),

etc.), and as such, its chemical and physical properties can vary greatly with time, region,

meteorology, and source (U.S. EPA 2009). Note that these guidelines are for non-speciated PM,

or PM reported as a total mass without distinguishing the morphology and chemical composition

of the PM (e.g., diesel engine PM, specific heavy metals, polychlorinated biphenyls, acidic

content of aerosols, etc.).

Figure 1. Schematic of Different Types of Particulate Matter

Source: U.S. EPA (https://www.epa.gov/pm-pollution/particulate-matter-pm-basics).

PM Guidance for ATSDR Health Assessment Products June 2024 update

PM is generally classified into three categories: ultrafine particles (UFP; particles with a mean

aerodynamic diameter (d

) of less than or equal to 0.1 micrometer (µm)), fine particles (PM

2.5

;

particles with a mean d

of less than or equal to 2.5 µm), and thoracic particles (PM

; particles

with a mean d

of less than or equal to 10 µm). Note that these size fractions are not mutually

exclusive—the “cut point” of the size fraction includes all sizes below it. For example, ultrafine

particles are a component of PM

2.5

. Particles that fall within the size range between PM

2.5

and

, are referred to as thoracic coarse particles (PM

10-2.5

; particles with a mean d

of ≤10 µm

and >2.5 µm). Particles ≤10 µm in aerodynamic diameter are considered respirable and pose the

greatest health concern because some can penetrate deep into the lungs and enter the blood

stream (U.S. EPA 2009). In ambient air, PM

2.5

tends to reflect regional air quality, with these

smaller particles traveling greater distances within the ambient atmosphere and remaining in the

atmosphere longer than larger particles and can be emitted directly from industry or formed

indirectly through chemical reactions in the atmosphere. PM

concentrations, however,

generally reflect the contribution of larger particles attributable to local sources.

In this guidance, PM

and PM

2.5

are addressed, but not UFP. UFP is not routinely characterized

for residential exposure assessment investigations because of limited atmospheric lifetime,

limitations in analysis, characterization of particles, and toxicity assessment, but it is an

important area of current research. These limitations have thus far precluded the development of

health-based screening values for UFP.

Exposure to respirable particles with an aerodynamic diameter less than 10 µm can affect both

short- and long-term effects on cardiopulmonary function, morbidity, and mortality. Numerous

scientific studies have linked particle pollution exposure to (U.S. EPA 2023a, WHO 2013):

▪ mortality and morbidity rate;

▪ ischemic heart disease, cerebrovascular disease, and heart failure;

▪ systemic inflammation, oxidative stress and alteration of the electrical processes of the

heart (the biomarkers of which illustrate the contribution of PM

2.5

exposures to

cardiovascular disease);

▪ respiratory effects (including aggravated asthma, decreased lung function, and symptoms

such as coughing) and infections;

▪ diabetes; and

▪ impaired neurological development in children and “brain aging” and neurological

disorders in adults.

ATSDR defines “sensitive” population subgroups as people who are more sensitive to the effects

of inhalation exposure to pollutants such as pregnant women, children, and older adults (≥65

years).

In addition, “highly sensitive” population subgroups may include members of these

groups or people in the general population that have pre-existing respiratory (e.g., asthma or

chronic obstructive pulmonary disease (COPD)) or cardiovascular disease. For several reasons

(e.g. greater urban and regional exposure in urbanized areas, less access to healthcare, greater

prevalence of respiratory and cardiovascular disease), people of lower socioeconomic status are

also more likely to have increased risk for adverse health outcomes from exposure to elevated

PM (Pratt et al. 2015). Studies also show that there are both PM

2.5

exposure and health risk

https://www.atsdr.cdc.gov/emes/public/docs/Sensitive%20Populations%20FS.pdf

PM Guidance for ATSDR Health Assessment Products June 2024 update

disparities by race and ethnicity among minority populations, specifically Black populations

(U.S. EPA 2022).

1.2. Purpose

These guidelines have been developed to aid health assessors in the evaluation of PM data during

the data screening phase of the health assessment process. It is intended to provide health

assessors with 1) some decision criteria for how to average PM data, 2) select appropriate

comparison values to screen PM data, and 3) guidance on how to reach conclusions about

whether a public health hazard can be attributed to PM exposure. Recommended public health

statements are provided for informing precautionary personal actions and suggested language are

provided for describing a finding that a site presents a public health hazard. Please note that

evaluating PM in addition to other pollutants is not addressed in this guidance. Health assessors

should refer to the ATSDR Framework for Assessing Health Impacts of Multiple Chemicals and

Other Stressors (Update) (2018)

for specific methods of conducting a multi-pollutant risk

evaluation.

2. Public Health Evaluation Approach for Particulate Data

2.1. Pre-evaluation

Before screening the data, health assessors should identify how the available data can be used to

contribute to the characterization of health risks in the community being evaluated. To determine

the applicability of the data for exposure assessment in carrying out a public health evaluation,

the following should be considered:

1. Monitor locations

▪ On-site monitors that represent occupational exposures to workers and are likely to be

an over-estimate of community exposures from fugitive releases from site operations.

▪ Perimeter or fenceline monitors are generally considered a proxy for the highest

exposure estimate for a nearby community from fugitive or short stack emissions.

With increasing stack height, combined with atmospheric transport and chemical

reactions, health assessors should keep in mind that the area of maximum impact may

be further within the adjacent community, not at the fence line.

▪ Residential monitors measure ambient PM levels where the general population,

including sensitive individuals, are exposed.

▪ Modeled maximum impact monitors (monitors placed at the location predicted by

modeling to have the highest concentrations) are intended to measure highest PM in

air and are usually sited using air dispersion modeling.

2. Frequency of downwind data collection/whether the data represent average or worst-

case conditions

▪ Meteorological (Met) data collocated at or close to the monitor location can help

health assessors determine whether the dataset they are evaluating represents

exposures for the most impacted residents. Modeling can be used to inform ambient

monitor placement in areas of high impact.

▪ Meteorological (Met) data should reasonably represent similar conditions to those at

the monitoring site but may or may not be collocated at the monitoring site. Note that

https://www.atsdr.cdc.gov/interactionprofiles/ip-ga/ipga.pdf

PM Guidance for ATSDR Health Assessment Products June 2024 update

U.S. EPA has siting requirements for stationary Met stations (see

https://www.epa.gov/sites/default/files/2020-10/documents/

volume_iv_meteorological_measurements.pdf).

3. Air quality monitors used for background/data context

▪ In addition to using weather conditions to help health assessors interpret ambient air

quality data, other area monitors can also help to put site-related PM data into

context. If PM levels seem high at a given site but other area monitors up and

downwind consistently have similarly high PM concentrations, the regional air

quality for that city or geographic area may be poor (the PM is likely not coming

solely from the facility being investigated). Looking at the data in context helps

health assessors come to appropriate conclusions regarding the hazard posed by the

site and helps to define appropriate health-protective recommendations.

▪ Spatial assessments of multiple datasets can help identify other sources affecting air

quality data. For example, evaluating concentration by wind direction may reveal the

influence of sites beyond the one being evaluated. Recommendations can be made to

more completely investigate other local or regional sources (e.g. traffic, electric

power generating, and other facilities) and can lead to additional data collection and

possible actions by regulatory agencies.

Health assessors should keep in mind that the evaluation of personal and community-related

exposures to PM is complicated because it is a ubiquitous class of air pollutant with wide

variation in both composition and concentration that is based on a mix of stationary, mobile, and

natural sources. Some PM in a community is the result of long-range mass transport that may

originate from multiple sources thousands of miles away (WHO 2006b). It is important for

health assessors to provide qualitative and semi-quantitative perspective in their assessments by

noting these limitations and acknowledging that many sources likely contribute to the PM

measured near the site under investigation, especially PM

, PM

2.5

, and UFP that could be

present from long-range transport. A spatial assessment of site and community data and a

comparison of these data with general air quality monitors in the area can provide important

context to the assessment of exposure.

Identifying whether the PM is source-related should be evaluated by considering:

a. Sampling of PM data should align with knowledge about the characteristics of emissions

from the source (e.g., continuous vs intermittent, hours of operation, etc.).

b. Whether there are other known sources of PM in the area (e.g., highways, industry,

agriculture, desert).

c. Whether there is directionality in the data (meteorological data versus concentration at

upwind/downwind locations).

d. If concentrations are relatively consistent, regardless of meteorological conditions, it may

suggest that the PM monitor represents regional air quality rather than a site-related source.

Health assessors should also compare site data to available data from other locations in the

United States. Recent and historic PM

and PM

2.5

data are summarized by the U.S. EPA and are

routinely shared with the public in the Our Nation’s Air annual trends reports. Data and maps

from these resources are presented in Appendix A. The health assessor is encouraged to put new

PM data into this historic and geographic context to show how they compare to similar site

scenarios.

PM Guidance for ATSDR Health Assessment Products June 2024 update

2.2. Process for Assessing PM Data

Prior to analysis, data should be confirmed to have been properly validated and be of high

quality. Three steps are outlined for the assessment of PM data: Data Averaging, Screening, and

Data Evaluation. See Figure 2 on the following page for a visual representation of this process.

Figure 2. Decision Tree for PM Assessments*

See page 8 for a discussion of data evaluation for <24-hour samples

PM Guidance for ATSDR Health Assessment Products June 2024 update

Health assessors should be aware that PM data are collected both as discrete and continuous data,

depending on the technology being used. Continuous data are generally reported hourly but can be

reported in other time increments. Filter-based samples are generally collected over a 24-hour

period and may not be collected over consecutive days (and one-in-three- and one-in-six-day

sampling are also common). However, filter-based sampling can also take place over other

averaging times as warranted by site-specific objectives.

2.2.1. Step 1: Data Averaging

As a first step, the health assessor must appropriately average the data prior to comparing them

to equivalent averaging times of screening values. Since more data points yield more accurate

averaging, it is preferable to use the most highly resolved increment for averaging into 1-hour,

24-hour, study period, and annual averages. For example, if data are collected in 1-minute

increments, one can average those measurements into a 1-hour, 24-hour, study period, and

annual averages.

2.2.2. Step 2: PM Screening

In Step 2, health assessors select contaminants for further evaluation by comparing them to

health-based comparison values (CV). ATSDR does not have a Minimal Risk Level (MRL)

value for PM that can be used as the basis for an ATSDR-derived CV. This guidance identifies

provisional CVs for PM that can be used for health assessment purposes.

The assessment of PM exposure can be

challenging because 1) includes emissions

from natural and anthropogenic sources and is

therefore ubiquitous across every region of the

world, whether or not there is a nearby

attributable source; and 2) since susceptibility

to PM exposure is highly variable from person

to person, and since there are no known

threshold of effect from exposure to PM of

varying composition, it is unlikely that any

standard or guideline value could lead to

complete protection for everyone (WHO

2006a). These factors make establishing a

health-based comparison value for PM complex.

WHO’s AQGs are based on health effects associated with PM exposure. For evaluating PM

data at sites, the WHO AQGs listed in Table 1 should be used for PM screening. The PM air

concentration for the appropriate data averaging timeframe for the specific PM size fraction

should be selected as the screening value. While WHO has used a statistical manipulation of the

AQG values to establish target ambient air concentrations (e.g., the 24-hour PM

2.5

AQG is the

percentile value over a given year), ATSDR and state cooperative agreement health

assessors should use the unadjusted values in Table 1 for PM screening. Note that acute

While regulatory values exist, such as U.S.

EPA’s National Ambient Air Quality Standards

(NAAQS) for PM, their purpose is to set

regulatory limits for six criteria pollutants,

including PM, for ambient air in the United

States. However, as a general practice, ATSDR

uses the most health-protective comparison

value available for screening purposes. For PM,

the most health-protective screening values

established are the Air Quality Guidelines

(AQGs) from the World Health Organization

(WHO) in Geneva.

PM Guidance for ATSDR Health Assessment Products June 2024 update

durations (≤24-hour averages) are evaluated with 24-hour AQGs, while chronic exposures to PM

are evaluated with annual AQGs. ATSDR often predicts “chronic” exposures with relatively

brief air sampling periods. For example, exposure investigations (EIs) have often used data

collected over weeks or months in downwind conditions to estimate long term exposure under

highest exposure conditions. The appropriateness of extrapolating acute or chronic health

implications from available data should be discussed along with the general attributes of the

dataset during the scoping process with a PM subject matter expert (SME). This discussion helps

determine the most appropriate analysis for the dataset being reviewed. PM has seasonal trends,

and limited data sets may over- or under-estimate PM exposures. Examples include elevated

2.5

and PM

in summer months in some areas of the country, or elevations of PM

2.5

(such as

EC, OC, and nitrates or sulfates) in winter or summer months, respectively.

Table 1. ATSDR PM Screening Values: World Health Organization Particulate Matter Air Quality

Guidelines (AQGs)*

PM Air Pollutant Metric WHO ATSDR CV

45 µg/m

(24-hour)

†

15 µg/m

(annual)

2.5

15 µg/m

(24-hour)

†

5 µg/m

(annual)

CV - Comparison value; µg/m

– micrograms per cubic meter; PM – particulate matter.

NA – Not Available: ATSDR does not have CV for PM.

*WHO 2021

†

These screening levels reflect the numeric value of the WHO AQGs for 24-hours

PM Guidance for ATSDR Health Assessment Products June 2024 update

2.2.2.1. Special consideration: Short-term exposure studies of ≤24-hour exposures

ATSDR health assessors often receive data collected over shorter

durations than 24 hours, but no sub-acute AQG exists for

exposures that occur for less than 24 hours. Continuous PM

and

2.5

data are frequently collected and reported over hourly

durations. If data are reported in increments less than an hour, data

should be averaged hourly. Hourly data highlight the variability of

PM concentrations over the course of a day and may identify

temporal trends of peak concentrations of PM that are not obvious

when evaluating 24-hour averages. In these instances, it is

appropriate to compare these short term (≤ 24 hour) exposures to

the acute AQGs. The rationale for this approach is discussed

below.

The 2019 PM U.S. EPA Integrated Science Assessment (ISA)

reviewed studies of short-term (≤24-hour exposures) PM exposure

in the scientific literature and their association with various health

outcomes. The studies evaluated in the ISA led U.S. EPA (2019)

to conclude that there is:

▪ sufficient evidence to conclude that a causal relationship

exists between short-term and long-term PM

2.5

exposure

and cardiovascular effects;

▪ likely to be causal relationship between short-term and

long-term PM

2.5

exposure and respiratory effects;

▪ likely to be causal relationship between long-term PM

2.5

exposure and neurological effects and cancer;

▪ a suggestive causal determination for short-term PM

10-2.5

exposure and cardiovascular effects, respiratory effects,

and mortality;

▪ mounting evidence that PM

2.5

and PM

10-2.5

may impair

nervous system function to varying degrees depending on

the size fraction; and

▪ evidence that PM

2.5

likely causes cancer and PM

10-2.5

has

evidence that is suggestive that it has carcinogenic

potential.

U.S. EPA (2019) identified exposures and health outcomes from

2.5

that are considered causal or likely to be causal.

See Table 2, below.

U.S. EPA. 2019. Integrated Science Assessment for Particulate Matter. Center for Public Health and

Environmental Assessment Office of Research and Development U.S. Environmental Protection Agency

Research Triangle Park, NC. Table 1-2.

In Summary:

Screening annual averages:

Screen long term (>1 year, or

if appropriate, shorter

durations (see Section 2.2.2))

average of PM

2.5

and

*against the annual

average AQG.

Screening 24-hour

averages:

Whenever possible, screen

the 24-hour PM

2.5

and PM

against the 24-hour AQG.

Screening ≤24-hour

averages:

Use 24-hour AQG for PM

2.5

and PM

and cite the 2019

U.S. EPA ISA using the

suggested precautionary

language: Given that the

literature suggests effects

have been observed at

concentrations at or below the

24-hour AQG for PM

2.5

and

(see U.S. EPA, 2019),

AQGs can be compared to

sample durations as short as

1-hour.

For PM1- levels exceeding the

annual AQG, see Section 2.2.3b

PM Guidance for ATSDR Health Assessment Products June 2024 update

Table 2. Summary of PM2.5 and health outcome studies*

Endpoint,

Exposure Duration

Endpoint Description

Mean ambient concentration range

associated with effects

Respiratory,

Short-term Exposure

Hospital admissions and ED

visits for asthma, COPD,

respiratory infections, and

combinations of respiratory-

related diseases

U.S. and Canada: 4.7−24. 6 μg/m³

Europe: 8.8−27.7 μg/m³

Asia: 11.8−69.9 μg/m³

Respiratory,

Short-term Exposure

Respiratory mortality

U.S. and Canada: 7.9−19.9 μg/m³

Europe: 8.0−27.7 μg/m³

Asia: 11.8−69.9 μg/m³

Respiratory,

Long-term Exposure

Decrement in lung function

growth

6−28 μg/m³

Respiratory,

Long-term Exposure

Asthma development in

children

5.2−16.5 μg/m³

Respiratory,

Long-term Exposure

Bronchitis symptoms in

children with asthma

9.9−13.8 μg/m³

Respiratory,

Long-term Exposure

Accelerated lung function

decline in adults

9.5−17.8 μg/m³

Respiratory,

Long-term Exposure

Respiratory mortality 6.3−23.6 μg/m³

Cardiovascular,

Short-term Exposure

Ischemic Heart Disease

5.8−18.6 μg/m³

Cardiovascular,

Short-term Exposure

Heart Failure 5.8−18.0 μg/m³

Cardiovascular,

Short-term Exposure

General cardiovascular

effects (over 2 hours)

24−325 μg/m³

Cardiovascular,

Long-term Exposure

Cardiovascular mortality: 4.1−17.9 μg/m³

Cardiovascular,

Long-term Exposure

Coronary events 13.4 μg/m³

Cardiovascular,

Long-term Exposure

CAC 14.2 μg/m³

Cardiovascular,

Long-term Exposure

CHD and stroke (people with

pre-existing disease)

13.4−23.9 μg/m³

Neurological,

Long-term Exposure

Brain volume 11.1−12.2 μg/m³

Neurological,

Long-term Exposure

Cognition 8.5 (5-yr avg)−14.9 μg/m³

Neurological,

Long-term Exposure

Autism 14.0−19.6 μg/m³

Cancer,

Long-term Exposure

Lung cancer incidence and

mortality

U.S. and Canada: 6.3−23.6 μg/m³

Europe: 6.6−31.0 μg/m³

Asia: 33.7 μg/m³

Mortality,

Short-term Exposure

Total mortality

U.S. and Canada: 4.37−17.97 μg/m³

Europe: 13−27.7 μg/m³

PM Guidance for ATSDR Health Assessment Products June 2024 update

Asia: 11.8−69.9 μg/m³

Mortality,

Long-term Exposure

Total mortality

ACS/HSC cohorts: 11.4−23.6 μg/m³

Medicare cohort: 8.12−12.0 μg/m³

Canadian cohorts: 8.7−9.1 μg/m³

Employment cohorts: 12.7−17.0 μg/m³

Excerpted from: U.S. EPA. 2019. Integrated Science Assessment for Particulate Matter. Center for Public Health

and Environmental Assessment Office of Research and Development U.S. Environmental Protection Agency

Research Triangle Park, NC. Table 1-2.

The most recent U.S. EPA assessment (2022) found that research published since 2019 further

supports evidence of causality between PM exposure and health effects. One PM

2.5

study showed

a relationship between long-term exposure and total mortality at levels averaging 5.9 ug/m

which is lower than the concentrations shown on Table 2. Another PM

2.5

study provided evidence

of both lung and cardiac function changes in young, healthy participants.

While fewer studies investigated health effects at ≤24-hour exposures, evidence suggests that

similar health outcomes are possible, including:

▪ heart rate variability;

▪ vasoconstriction of arteries; and

▪ hemostatic markers indicating changes in the blood of healthy subjects or patients with

coronary artery disease.

These effects were observed in single and multi-city continuous measurements where morbidity

was assessed from the general population and in controlled human and animal exposure studies.

The continuous or controlled acute exposures included durations of observation between 1 and

22 hours. Given that the literature suggests effects have been observed at concentrations at or

below the 24-hour WHO AQG for PM

2.5

and PM

, health assessors can apply these screening

values to ambient concentrations collected over a duration as short as 1-hour. However,

whenever possible, the health assessor should also calculate and compare 1-hour and 24-hour

averages to the 24-hour AQG and annual averages to the annual AQG for PM

2.5

and PM

Exposure to daily averages has been better studied for all outcomes and has resulted in a more

robust scientific database for the effect of PM on health outcomes. These associations are

generally stronger for PM

2.5

than for PM

(U.S. EPA 2019; WHO, 2013).

2.2.3. Step 3: Data Evaluation

2.2.3.1. Acute exposures

To evaluate acute exposures in a given dataset, health assessors should assess general air quality

over the duration that sampling was conducted. U.S. EPA’s PM Air Quality Index (AQI) is used

nationally to designate real time threats to unusually sensitive

individuals, sensitive populations,

The U.S.EPA does not have a formal definition of an unusually sensitive person, however, we know from scientific

studies that there is inter-individual variability in responses to exposure to air pollution. For example, two people

could respond differently to the same air pollution level: one person with asthma may experience some respiratory

discomfort and maybe an asthma attack while another person with asthma exposed to the same level may not

react at all. The intent of adding in the cautionary statement is to advise highly sensitive persons that they should

PM Guidance for ATSDR Health Assessment Products June 2024 update

or the general public. Identifying the number of days during the sampling period being evaluated

where ambient PM levels fall into these AQI categories can support a qualitative assessment of

the frequency that poor air quality occurred in the monitoring area. This qualitative assessment

puts exceedances of the AQGs in perspective. For example, if during screening, the health

assessors identifies exceedances of the 24-hour AQGs, but those exceedances only occurred

infrequently, the health assessor may choose to use cautionary statements indicating that any

harm to sensitive individuals was limited to a few days over a year of sampling. However, if

exceedances occur over substantial portion of the air samples, the health assessor should choose

stronger hazard language.

Depending on the PM level, any single 24-hour period above the WHO AQG potentially could

result in harmful effects for either highly sensitive or sensitive individuals, the general (healthy)

public, or all for all groups. The frequency with which ambient PM fell into the various AQI

categories can be presented by adding the number of days in a given sampling period that PM

levels fall within the AQI categories shown in Appendix B. Additional perspective on how data

near a site compare to areas not expected to be impacted by known sources of PM should also be

provided (see Background Air Considerations section and Appendix A). Please consult with a

PM SME for help interpreting acute exposures and the AQI categories in Appendix B.

Additional perspective on how data near a site compare to areas not expected to be impacted by

known sources of PM should also be provided (see Background Air Considerations section and

Appendix A).

Appendix B defines the following to be used in PM assessments:

▪ AQI Category and associated PM ranges

▪ Sensitive/highly sensitive group definition

▪ Health effects statements

The information in Appendix B should be included in a health consultation or health assessment.

The cautionary statements in section 3.0 should be considered for use with the recommendations.

For 24-hour PM

levels in the Moderate AQI range, health assessors should provide the public

with a cautionary statement for highly sensitive persons (see Appendix B). The health effects

statement for the moderate category should be added to a conclusion, basis for a conclusion, or

public health action plan and the cautionary statement should be added as a recommendation.

Note that the upper end of the AQI “Good” category slightly exceeds the 24-hour AQGs for

and PM

2.5

. This limitation should be acknowledged in the health consultation with the

following caveat:

“The AQI is a tool used by U.S. EPA to categorize air quality threats in real time to local

populations across the United States and is not intended to be used as a surrogate for a

presentation of the scientific literature in health assessments. ATSDR uses the AQI only for the

always be cognizant of how they are feeling outdoors on days in the Moderate AQI Category. Instead of using the

undefined term “unusually sensitive”, ATSDR uses “highly sensitive” throughout this guidance.

PM Guidance for ATSDR Health Assessment Products June 2024 update

purposes of qualitatively assessing the frequency of poor air quality days that may affect

different segments of the population. AQI data can be used to support health conclusions made

by evaluation of exceedances of screening values, an assessment of how exposures compare to

those in the toxicological literature, and an assessment of other data that put these exceedances

into context (such as background data or upwind data vs. downwind data, spatial analysis,

etc.).”

2.2.3.2. Chronic exposures

There are no annual AQI designations to support health conclusions for chronic PM

exposures

exceeding the AQGs. As previously stated, for long-term health effects there are stronger

correlations with PM

2.5

than with PM

levels. However, WHO has maintained their annual

average PM guideline level of 15 µg/m

primarily to protect against harmful PM

2.5-10

exposures.

If a health assessor is presented with only PM

data, they should first evaluate the 24-hour

averages and less than 24-hour averages (usually 1-hour) using the approach described above.

Then annual average PM

data should be compared to the annual WHO AQG to get a sense of

whether the PM

annual averages are a potential concern, but also note that many areas of the

U.S. have annual average PM

levels above the WHO guideline (see Appendix A).

To draw conclusions on annual PM

data, health assessors should consult with one of the PM

SMEs. Further, an assessment of background data, upwind data vs. downwind data, spatial

analysis, etc. helps to determine the extent of contribution from a specific source to air quality

and informs health-protective recommendations.

3. Integrating steps 1-3 and adding cautionary statements

Data evaluated in the PM assessment will fall into one of two scenarios. These scenarios and the

appropriate next steps are detailed below. Refer to Figure 2 for an overview of the decision

process for PM Assessment.

3.1. Scenario 1: The appropriately averaged data are consistently below AQGs

The assessor would conclude that exposures are not expected to harm the public in the absence

of data and information indicating otherwise. Current science does support evidence that

increases in harmful effects are possible for highly sensitive populations at concentrations below

the AQGs.

Evaluating less than 24-hour PM data when the 24-hour average is below the AQGs.

Neither the U.S. EPA nor the WHO have developed standards or guidelines for exposures to PM

for durations less than 24-hours. However, 24-hour AQGs for PM

2.5

and PM

can also be used

for PM screening for shorter durations. Given that the literature suggests effects have been

observed at concentrations at or below the 24-hour AQG for PM

2.5

and PM

(see U.S. EPA

2019), AQGs can be compared to sample durations as short as 1-hour. Because a health

conclusion is only made based on a sampling average equivalent to the AQG duration of 24-

PM Guidance for ATSDR Health Assessment Products June 2024 update

hours, a cautionary statement to alert potentially sensitive populations can be added in the

scenario where hourly averages may exceed the acute AQG, but the 24-hour average is below the

acute AQG.

Suggested language:

Conclusion: “PM

levels had maximum 1-hour concentrations of over X,XXX µg/m

: however,

24-hour averages were below the AQG. Exposure to PM levels above the AQG has the potential

to trigger acute health conditions in highly sensitive and sensitive individuals, even over

exposure periods of less than 24 hours (U.S. EPA 2012).” OR

“Individuals with cardiopulmonary illness may have a slightly increased risk of the

exacerbation of their health conditions with intermittent short-term exposures to high

concentrations of pollutants over acute durations (<24 hours). It is possible that shorter

duration exposures (e.g. 1-hour) to very high PM concentrations could trigger an adverse acute

response in these populations in the absence of an exceedance of the 24-hour AQG.”

Recommendation: See Appendix B; Example: Highly sensitive people and parents of highly

sensitive children should consult the air quality forecast and consider reducing prolonged or

heavy exertion on days where air quality is predicted to be poor.

Consult with PM SME if help is needed to interpret acute (< 24-hour) data.

3.2. Scenario 2: The appropriately averaged data are above AQGs:

The assessor may conclude that harmful health effects are possible based on one or more of the

following considerations:

1. Frequency of concentrations at levels of concern to specific populations at risk in the

community. The health assessor should include the frequency of AQG exceedances as

well as the frequency 24-hour averages fall within the various AQI categories.

2. Meteorological and spatial data indicating that a sole source is responsible for a great

proportion of PM and levels approaching the PM CVs.

3. The dataset is small but meteorological and spatial data indicate that worst-case

conditions are not necessarily occurring during the sampling period.

4. Sensitive individuals have an increased likelihood of experiencing health effects as a

result of exposures (e.g., persons with severe asthma, COPD, and pre-existing respiratory

or cardiovascular disease).

The outcome of this evaluation could include a conclusion that a health hazard does or does not

exist, the inclusion of a cautionary statement for the public, and/or a request for additional

sampling data to confirm whether a hazard may exist. The scenario should be prefaced with a

statement about the representativeness of the data (e.g., it represents worst case conditions, it

doesn’t represent worst case conditions, the monitors were not operating when exposures were

occurring, the facility installed pollution controls prior to monitoring beginning, etc.). An

assessment of short-term exposure data should use cautionary language from the AQI table in

Appendix B.

▪ Short term (24 hour) averages:

PM Guidance for ATSDR Health Assessment Products June 2024 update

Suggested language:

Conclusion: “Exposure to elevated concentrations of PM

2.5

and/or PM

could harm

public health because of an increased risk for adverse health effects among [insert site-

specific population of concern].

See Appendix B for AQI categories to evaluate air quality in the population being

assessed and for possible additional language for the conclusion.

AND

Recommendation: “Highly sensitive people should consult the air quality forecast and

consider reducing prolonged or heavy exertion on days where air quality is predicted to

be poor.

▪ Long term (annual) averages:

Suggested language (long term):

Conclusion: Prolonged exposures to PM above the AQGs may slightly increase the

likelihood of harm for individuals with pre-existing health conditions, such as

cardiopulmonary disease.”

AND

Recommendation: “Sensitive individuals should consider reducing prolonged or heavy

physical activity on days with moderate to unhealthy air quality.”

Health assessors can include a link to the AQI website where residents can look up

projected air quality in their zip code at https://www.airnow.gov/aqi/aqi-basics/.

3.3. Example language

These guidelines supersede all previous screening values and screening approaches. Several

ATSDR documents have been published evaluating PM exposures that include well-constructed

write-ups of health implications. Health assessors are encouraged to review the language used in

these documents to discuss the types of health effects possible at site-specific concentrations.

Note that these documents may not have used the updated approach for PM assessment outlined

in this guidance, so it is recommended to review these documents as examples for how to draft

the document Health Implications section. Health assessors should always review the most

recent U.S. EPA Integrated Science Assessment for PM when drafting this section to ensure the

most recent science is presented in their document. Health Assessors should request guidance

from an PM Subject Matter Expert if needed.

4. References

Dockery DW et al. (1993). An association between air pollution and mortality in six U.S. cities. New

England Journal of Medicine, 329(24):1753–1759.

To draw health conclusions on annual PM

data, health assessors should consult with one the PM SMEs. This is

because the strongest correlations with chronic PM exposures and adverse health outcomes are associated with

smaller particle fraction sizes (≤ PM

2.5

) and that the PM

AQG is exceeded regularly across the United States.

PM Guidance for ATSDR Health Assessment Products June 2024 update

Jerrett M et al. (2005). Spatial analysis of air pollution and mortality in Los Angeles. Epidemiology,

16(6):727–736.

Pope CA 3rd et al. (2002). Lung cancer, cardiopulmonary mortality, and long-term exposure to fine

particulate air pollution. Journal of the American Medical Association, 287(9):1132–1141.

Pratt G., Valdali M., Kvale D., et al. 2015. Traffic, air pollution, minority and socio-economic status:

Addressing inequities in exposure and risk. Int J Environ Res Public Health, 12(5): 5355–5372.

U.S. EPA. 2009. Particulate Matter National Ambient Air Quality Standards:

Scope and Methods Plan for Urban Visibility Impact Assessment. EPA-452/P-09-001. February 2009.

Available at: https://www3.epa.gov/ttn/naaqs/standards/pm/data/20090227PMNAAQSWelfare.pdf.

U.S. EPA. 2012. Provisional Assessment of Recent Studies on Health Effects of Particulate Matter

Exposure. EPA/600/R-12/056F. December 2012. Available at

http://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=508978

U.S. EPA. 2019. Integrated Science Assessment for Particulate Matter. U.S. Environmental Protection

Agency. EPA/ 600/R-08/139F. December 2019. Available at https://www.epa.gov/isa/integrated-science-

assessment-isa-particulate-matter.

U.S. EPA. 2022. Supplement to the 2019 Integrated Science Assessment for Particulate Matter. U.S.

Environmental Protection Agency. EPA/600/028. May 2022. Available at

https://www.epa.gov/isa/integrated-science-assessment-isa-particulate-matter.

U.S. EPA. 2023a. Particulate Matter Pollution. Health and Environmental Effects. Updated August 2023.

Available at https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm.

U.S. EPA. 2023b. Our Nation’s Air – Trends Through 2022. 2023. Available at:

https://gispub.epa.gov/air/trendsreport/2023/#home

U.S. EPA. 2024. Pre-generated Data Files. April 2024. Available at:

https://aqs.epa.gov/aqsweb/airdata/download_files.html

WHO. 2006a. WHO Air Quality Guidelines for Particulate Matter, Ozone, Nitrogen Dioxide, and Sulfur

Dioxide. Global Update: 2005. World Health Organization. 2006. Available at

https://apps.who.int/iris/handle/10665/69477.

WHO. 2006b. Health Risks of Particulate Matter from Long-Range Transboundary Air Pollution. World

Health Organization. Copenhagen, Denmark. Available at:

https://www.who.int/publications/i/item/E88189.

WHO. 2013. Review of Evidence on Health Aspects of Air Pollution—REVIHAAP Project Technical

Report. World Health Organization. 2013. Available at

https://www.ncbi.nlm.nih.gov/books/NBK361805/.

WHO. 2021. Global Air Quality Guidelines. Particulate matter (PM

2.5

and PM

), Ozone, Nitrogen

dioxide, Sulfur dioxide, and Carbon Monoxide. Geneva: World Health Organization; 2021: License:

CC BY=NCSA3.0 IGO.

PM Guidance for ATSDR Health Assessment Products June 2024 update

Appendix A: Particulate Matter National Data Summaries from the U.S. EPA

Air Quality System (AQS)

State and county environmental agencies that conduct regulatory air monitoring are required to

submit their data to U.S. EPA’s Air Quality System (AQS). U.S. EPA uses these data to

determine attainment of the NAAQS and also for public air quality reports. Particulate matter

data are included in EPA’s annual report titled “Our Nation’s Air” (EPA 2023b). These findings

are summarized below and health assessors may access future versions national maps and

individual site summaries, are presented in U.S. online (https://www.epa.gov/air-trends). Health

assessors should use these resources to put their PM data into a regional and national context.

Figure A1 shows the 1990-2022 trend in peak 24-hour PM

concentrations nation-wide. The

data are based on the second highest 24-hour concentration at each monitoring site, which is the

metric used by U.S. EPA to determine attainment of the PM

24-hour NAAQS of 150 ug/m

The figure shows the average and median concentration for each year for national trend sites, as

well as the 10

and 90

percentiles. Underlying data are shown on Table A1 and are also

accessible via the Our Nation’s Air website. The average peak 24-hour PM

concentration has

declined 34% during the trend period. The annual average consistently exceeds the WHO AQG

of 45 ug/m

. The median peak 24-hour PM

concentration has decreased 35% and has been

approximately equal to the AQG since 2009.

The geographic distribution of peak 24-hour PM

concentrations in 2022 is shown on Figure

A2. This map is also located on the Our Nation’s Air website where it is interactive (see:

https://gispub.epa.gov/air/trendsreport/2023). Health assessors can click on individual monitor

sites on the web map to see the peak PM

concentration in 2022 or previous years. Note that the

lowest concentration break point on the map is higher than the AQG of 45 ug/m

, however it is

evident that many urban areas have monitors with a PM

24-hour average higher than the AQG.

Several locations, mostly in California and the Pacific Northwest, are reporting PM

24-hour

peaks over 255 ug/m

i.e. more than five times the AQG.

U.S. EPA does not have an annual PM

NAAQS and thus does not track trends for annual

average PM

concentrations. ATSDR pulled this information from AQS as presented on Table

A3 (EPA 2024). ATSDR included all sites with sufficient data completeness and avoided

duplicates by averaging data for multiple monitors at each site. Beginning in 2011, 56% of PM

sites had an annual average higher than the AQG of 15 ug/m

. The concentrations have slightly

declined over the years to where 47% exceeded the AQG in 2022.

Figure A3 shows the 2000-2022 trend in peak 24-hour PM

2.5

concentrations nation-wide. The

data are based on the 98

percentile of 24-hour concentration at each monitoring site over a 3-

year period, which is the metric used by U.S. EPA to determine attainment of the PM

2.5

24-hour

NAAQS of 35 ug/m

. The figure shows the average and median concentration for each rolling 3-

year period for national trend sites, as well as the 10

and 90

percentiles. Underlying data are

shown on Table A4 and are also accessible via the interactive graphics on the Our Nation’s Air

website. The median peak 24-hour PM

2.5

concentration has declined 46% since 2000, however it

remains above the WHO AQG of 15 ug/m

. The 90

and 10

percentiles have also decreased;

the 10

percentile has consistently been below the AQG since 2014.

PM Guidance for ATSDR Health Assessment Products June 2024 update

The geographic distribution of peak 24-hour PM

2.5

concentrations in 202221 is shown on Figure

A4. Health assessors may access the interactive version of this map in the Our Nation’s Air

report online to determine whether monitor sites in the area of interest are exceeding the WHO

AQG of 15 ug/m

Figure A5 shows the 2000-2022 trend in annual average PM

2.5

concentrations nation-wide. The

data are based on the 3-year average concentration at each monitoring site, which is used by U.S.

EPA to determine attainment of the PM

2.5

annual NAAQS. U.S. EPA lowered the NAAQS from

12 to 9 ug/m

in February 2024 and is currently implementing this revised standard The previous

NAAQS is marked on Figure A5. The figure shows the average and median concentration for

each year for national trend sites, as well as the 10

and 90

percentiles. Underlying data are

shown on Table A5 and are also accessible via the interactive graphics on the Our Nation’s Air

website. The median annual PM

2.5

concentration has declined 45% and remains above the WHO

AQG of 5 ug/m

The 10

percentile also remains above the AQG.

The geographic distribution of annual average PM

2.5

concentrations in 2022 is shown on Figure

A6. Health assessors may access the interactive version of this map in the Our Nation’s Air

report online to determine whether monitor sites in the area of interest are exceeding the WHO

AQG of 5 ug/m

The data presented in these figures and tables can be used by health assessors to place measured

concentrations from a given site in context, both by the type of site and the year measurements

were collected. It is expected that most sites will have some days that exceed the 24-hour

screening levels and a discussion of typical concentrations at other sites in the United States may

be useful to residents when evaluating measurements in their communities.

Figure A1. Peak 24-hour PM

concentrations in the U.S., 1990-2022, ug/m

*The “Most Recent National Standard” refers to the current 24-hour PM

National Ambient Air Quality

Standard of 150 ug/m

. The data trend is based on monitoring sites nationwide measuring PM

that have

sufficient data to assess PM

trends since 1990.

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

PM Guidance for ATSDR Health Assessment Products June 2024 update

Table A1. Peak 24-hour PM

concentrations in the U.S., 1990-2022, ug/m

Year Median Average 90

percentile 10

percentile

1990

79 89 162 45

1991

81 86 134 45

1992

69 75 115 38

1993

66 74 124 33

1994

64 74 127 34

1995

63 75 134 37

1996

56 65 106 32

1997

59 67 115 36

1998

56 63 106 36

1999

56 68 109 38

2000

58 66 107 35

2001

55 64 97 36

2002

56 62 96 35

2003

56 68 123 31

2004

50 57 95 29

2005

56 60 98 32

2006

49 60 101 34

2007

57 65 112 29

2008

50 57 87 31

2009

45 51 82 25

2010

47 49 73 27

2011

46 57 90 30

2012

46 54 91 28

2013

42 60 101 25

2014

44 57 102 25

2015

46 56 78 29

2016

46 54 91 24

2017

52 59 98 24

2018

48 69 172 27

2019

45 47 73 23

2020

50 69 120 24

2021

49 62 124 25

2022

51 59 97 25

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

PM Guidance for ATSDR Health Assessment Products June 2024 update

Figure A2. Peak 24-hour PM

concentrations in the U.S., 2022, ug/m

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

Table A3. Percent of PM

Monitoring Sites in the U.S. with Annual Average Concentration

Exceeding WHO AQG, 2011-2020

Year

Number of

Sites

Percent of Sites Exceeding

AQG of 15 µg/m

2011 440 56

2012 487 57

2013 432 51

2014 370 51

2015 369 47

2016 355 47

2017 345 50

2018 373 48

2019 317 47

2020 213 71

2021 346 55

2022 346 47

PM Guidance for ATSDR Health Assessment Products June 2024 update

Source: U.S. EPA. 2024. Pre-generated Data Files. April 2022. Available at:

https://aqs.epa.gov/aqsweb/airdata/download_files.html

Figure A3. Peak 24-hour PM

2.5

concentrations in the U.S., 2000-2022, ug/m

*The “Most Recent National Standard” refers to the current 24-hour PM

2.5

National Ambient Air Quality

Standard of 35 ug/m

. The data trend is based on monitoring sites nationwide measuring PM

2.5

that have

sufficient data to assess PM

2.5

trends since 1990.

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

Table A4. Peak 24-hour PM

2.5

concentrations in the U.S., 2000-2022, ug/m

Averaging period Median Average 90

percentile 10

percentile

2000 33.7 35 47 22.3

2001 34.3 36 47.7 23

2002 33.2 34 46.6 22

2003 31.6 32 42.1 19.3

2004 30.5 31 40.6 21

2005 33.9 34 44.7 19.55

2006 29.8 30 38.7 19.2

2007 31.3 32 41.2 20.6

2008 26.9 28 35.4 17.8

2009 23.8 25 35.1 16.7

2010 24.6 25 33.4 15.9

2011 24.3 25 32.4 16.1

2012 21.4 22 28.5 16

2013 21 23 30 15.7

2014 21.2 23 29.2 15.2

2015 21.4 22 29.5 15.2

2016 18 19 25.8 13.3

2017 18.4 21 30.9 14.2

2018 19.7 23 32.1 14.4

PM Guidance for ATSDR Health Assessment Products June 2024 update

2019 18.7 20 26.5 13.7

2020 19 25 42.4 14

2021 21.1 23 33.4 15.4

2022 18.2 20 27.5 13.3

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

Figure A4. Peak 24-hour PM

2.5

concentrations in the U.S., 2022, ug/m

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2021

Figure A5. Annual average PM

2.5

concentrations in the U.S., 2000-2022, ug/m

PM Guidance for ATSDR Health Assessment Products June 2024 update

*The “Most Recent National Standard” refers to the previous annual PM

2.5

National Ambient Air Quality

Standard of 12 ug/m

, which was lowered to 9 ug/m

in February 2024. The data trend is based on

monitoring sites nationwide measuring PM

2.5

that have sufficient data to assess PM

2.5

trends since 2000.

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

Table A5. Annual average PM

2.5

concentrations in the U.S., 2000-2022, ug/m

Averaging period Median Average 90

percentile 10

percentile

2000

14 14 18 8.8

2001

13 13 17 8.9

2002

13 13 17 8.8

2003

13 12 16 8.0

2004

12 12 16 7.8

-2005

13 13 17 7.8

2006

12 12 15 7.9

2007

12 12 16 7.5

2008

11 11 14 7.5

2009

9.9 10 12 6.9

2010

10 10 13 6.7

2011

10 10 12 6.8

2012

9.3 9.2 12 6.7

2013

8.9 9.0 11 6.4

2014

9.0 8.9 11 6.2

2015

8.6 8.6 11 6.2

2016

7.7 7.8 9.7 5.6

2017

7.9 8.1 10 6.0

2018

8.0 8.3 11 6.3

2019

7.6 7.7 9.5 5.8

2020

7.6 8.1 11 5.9

2021

8.3 8.5 11 6.3

2022

7.7 7.8 10 5.8

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

PM Guidance for ATSDR Health Assessment Products June 2024 update

Figure A6. Annual average PM

2.5

concentrations in the U.S., 2022, ug/m

Source: U.S. EPA. 2021a. Our Nation’s Air – Trends Through 2022. 2023b. Available at:

https://gispub.epa.gov/air/trendsreport/2023

PM Guidance for ATSDR Health Assessment Products June 2024 update

Appendix B: U.S. Environmental Protection Agency Particulate Matter AQI designations and Health

Statements*

AQI