xvEPA

Indicators of Environmental Health Disparities: Population in
Monitored Counties Meeting PM2.5 National Ambient Air Quality
Standards (NAAQS)

About the Indicators of Environmental Health Disparities

EPA's indicators of environmental health disparities aim to illustrate disparities in key environmental and
public health conditions across race/ethnicity and socioeconomic status, as well as the relationship
between these health outcomes and the work of EPA programs. This project was created in direct
response to EPA's 2022-2026 Strategic Plan. These indicators are intended solely as an informational tool
and are not intended to be the basis for agency decision making. EPA does not, consistent with
applicable laws, distribute governmental benefits or burdens based on race, color, national origin, or sex.

Background Information

Particulate Matter (PM) describes the solid and liquid particles found in the air. Some of the particles are
visible in the air while others are so small they can be only detected using an electron microscope. PM2.5
are fine particles that have an aerodynamic diameter of 2.5 micrometers or smaller; for comparison the
average human hair is about 70 micrometers in diameter.1 Some PM2.5 particles are referred to as
"primary" particles because they are emitted directly into the atmosphere from sources like cars,
industrial facilities, and forest fires. However, most particles are secondary particles, which are created
from complex reactions between pollutants like sulfur dioxide and nitrogen oxides in the atmosphere.
The composition of particulate matter in the U.S. can depend on both geologic location and seasonality.2
Under the Clean Air Act, the EPA sets the National Ambient Air Quality Standards (NAAQS) for all criteria
air pollutants, including PM2.5-3

Inhaling PM2.5 poses a risk to human health because PM2.5 can travel deep into the lungs and enter the
blood stream.2 Exposure to PM2.5 can impact many organ systems, including the lungs and heart, leading
to conditions such as nonfatal heart attacks, irregular heartbeats, aggravated asthma, decreased lung
function, increased respiratory symptoms, and premature death for those with preexisting heart and
lung conditions.4 Individuals with existing heart or lung disease, children, older adults, and people with a
lower socioeconomic status are all more likely to be impacted by particulate exposure.2,3 Exposure to
PM2.5 contributes significantly to the quantified burden of disease due to air pollution in the U.S.4 and
worldwide.5

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Figure 1. PM2.5 NAAQS by Race

Percent

100

0

African American
87.9%

White
87.3%

| Native American
80.7%

I Other, Including
Multiple races
76%

2008 I 2010 I 2012 I 2014 I 2016 I 2018 I 2020 I 2022

2009 2011 2013 2015 2017 2019 2021 2023

Data Note: Data points for this indicator are 3-year averages. This graph
plots each 3-year average in its last year.

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Figure 2. PM2.5 NAAQS by Ethnicity

Percent

2009 2011 2013 2015 2017 2019 2021 2023

Data Note: Data points for this indicator are 3-year averages. This graph
plots each 3-year average in its last year.


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Figure 3. PM2.5 NAAQS by Poverty Level

Percent

2008 I 2010 I 2012 I 2014 I 2016 I 2018 I 2020 I 2022

2009 2011 2013 2015 2017 2019 2021 2023

Data Note: Data points for this indicator are 3-year averages. This graph
plots each 3-year average in its last year.

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What these charts show

These figures show the percentage of the U.S. population living in monitored counties meeting the 2012
annual and 2006 24-hour PM 2.5 NAAQS, characterized both by socioeconomic groups and racial and
ethnic groups. The percentage of the population living in monitored counties meeting the PM2.5 NAAQS
is not equal across different racial/ethnic and socioeconomic groups. Comparisons with the NAAQS are
based on PM2.5 design values - three-year averages computed from monitored concentrations - which
represent the air quality at a given location relative to the NAAQS. The population estimates are for the
final year of the three-year air quality value, obtained from 2010 U.S. Census county-level population
data.6

•	Between the 2008 baseline and 2016, the percentage of the U.S. population living in monitored
counties meeting PM 2.5 NAAQS increased from just over 40% to just over 90%.

•	After 2016, the percentage of the U.S. population living in monitored counties meeting PM 2.5
NAAQS decreased but has remained above 80%. The change observed since 2016 corresponds
to an increase in particle pollution in many areas associated with increased wildland fire impact.

•	In 2023, African American (87.9%) and white populations (87.3%) had the highest percentages of
populations living in monitored counties meeting PM2.5 NAAQS (Figure 1); both percentages
were higher than the Native American population (80.7%), and the Other population category
(including multiple races) (76%) (Figure 1).

•	While 88.4% of the non-Hispanic population lives in monitored counties meeting the PM2.5
NAAQS, only 73.5% of the Hispanic population lives in monitored counties meeting the NAAQS
(Figure 2).

•	Finally, 86.5% of the population that is two times the poverty level7 or higher lives in monitored
counties meeting PM2.5 NAAQS, while 82.8% of the population below two times the poverty level
(i.e., low socioeconomic status) lives in those counties (Figure 2).

What these charts do not show

These charts are a historical record and do not explain why certain racial/ethnic and socioeconomic
groups are disproportionately living in monitored counties meeting PM2.5 NAAQS, compared to those
that do not live in those counties. Nonattainment areas with higher concentrations of PM2.5 contain a
higher population of people that are below two times the poverty level, and the proportion of people of
low socioeconomic status to other people in nonattainment areas has risen steadily. Thus, as more
counties come into attainment, the remaining nonattainment areas with higher concentrations of PM2.5
highlight a potential disparity in health protection. Further information on monitored counties achieving
PM2.5 NAAQS can be found in EPA's Green Book. EPA also publishes extensive information about trends
in key air pollutants, as well as trends in emissions in all areas.

Relevant EPA Activities

The EPA is engaged in activities to reduce exposure to PM2.5 with a specific focus on addressing
disparities. Some of these key activities include:8

•	Regulating criteria air pollutants and their precursors: Under the Clean Air Act, the EPA sets the
National Ambient Air Quality Standards (NAAQS) for criteria air pollutants and works with state
and local air quality management agencies to meet those standards. These standards specify the
maximum amount of PM in outdoor air. The EPA reviews and updates these standards
periodically to ensure they provide adequate protection for people and the environment. Areas
within every state are assessed to determine whether or not they are meeting these standards;

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those areas that do not meet these standards are considered "nonattainment areas" and are
listed in the Green Book. States are required to submit State Implementation Plans (SIPs)
consisting of programs and policies used to attain and maintain the NAAQS.9 In 2024, the EPA
updated the primary, or health-based, standard for PM2.5 from 12 micrograms per cubic meter to
9 micrograms per cubic meter. EPA is now in the process of implementing the revised standard.

•	Researching air pollutants: The EPA helps lead research on air pollutants and emissions that
inform air quality regulations and strategies. This includes air monitoring and emissions, air
quality modeling, and the health effects from air pollution exposure.

•	Developing public education tools: The EPA has several public education tools available to
access data on air pollution. In partnership with other agencies, the EPA helps contribute to
Air Now, a website that provides Air Quality Index (AQI) data on city, state, and national levels.
People can use AirNow to determine how clean or polluted their outdoor air is and to take
action to protect their health. EPA has also released a wildland fire air pollution tool: the Fire and
Smoke Map.

For further information on indicators related to environmental and human health, explore EPA's Report
on the Environment, and for further information on indicators related to children's environmental health,
explore EPA's America's Children and the Environment (ACE) report.

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References

1)	U.S. EPA. United States Environmental Protection Agency. Particulate Matter (PM) Basics. US EPA.
Published July 11, 2023. Accessed June 19, 2024. https://www.epa.gov/pm-
pollution/particulate-matter-pm-basics.

2)	U.S. EPA. Integrated Science Assessment (ISA) for Particulate Matter (Final Report, Dec 2019).
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.

3)	U.S. EPA. Process of Reviewing the National Ambient Air Quality Standards. U.S. EPA. Published
January 19, 2014. Accessed July 19, 2024. https://www.epa.gov/criteria-air-pollutants/process-
reviewing-national-ambient-air-qualitv-standards

4)	National Institute of Environmental Health Sciences. Air Pollution and Your Health. National
Institute of Environmental Health Sciences. Updated July 12, 2024. Accessed July 22, 2024.
https://www.niehs.nih.gov/health/topics/agents/air-pollution.

5)	Lim, Stephen S et al. A comparative risk assessment of burden of disease and injury attributable
to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the
Global Burden of Disease Study 2010. 2012. The Lancet. 380(9859):2224-60. doi:

10.1016/S0140-6736(12)61766-8. Accessed September 12th, 2024.

6)	U.S. Census. (2010). County population totals, https://www.census.gov/programs-
surveys/popest/technical-documentation/research/evaluation-estimates/2020-evaluation-
estimates/2010s-counties-total.html

7)	U.S. EPA. Process of Working with Areas to Attain and Maintain NAAQS (Implementation
Process). U.S. EPA. Published April 14, 2014. Accessed July 1, 2024.

https://www.epa.gov/criteria-air-pollutants/process-working-areas-attain-and-maintain-naaqs-
implementation-process.

8)	EO 14096 directs agencies to identify, analyze and address disproportionate and adverse human
health and environmental effects, as appropriate and consistent with applicable law. Thus, as
appropriate, EPA may consider disparities in its activities.

9)	Following the Office of Management and Budget's (OMB) Statistical Policy Directive 14. the
Census Bureau uses a set of money income thresholds that vary by family size and composition
to determine who is in poverty. If a family's total income is less than the family's threshold, then
that family and every individual in it is considered in poverty. The official poverty thresholds do
not vary geographically, but they are updated for inflation using the Consumer Price Index (CPI-
U). For more information, see: How the Census Bureau Measures Poverty.

United States Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460

EPA 231R24006
December 2024
www.epa.gov

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