Air Monitoring
Air Monitoring in Chattanooga–Hamilton County, Tennessee
Overview
The Bureau monitors air quality levels for Chattanooga–Hamilton County, Tennessee to ensure that pollution concentrations remain in compliance with the Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM2.5) and ozone.
Air quality monitoring is conducted continuously to assess pollutant levels, support public health protection, and ensure adherence to federal air quality standards.
Historical Air Quality Context
Chattanooga has experienced significant changes in air quality over time.
Historically, the region’s economy was strongly supported by manufacturing, steel production, and transportation-related industries. These activities contributed to elevated levels of air pollution, and at times in the mid-to-late 20th century, Chattanooga was identified among areas in the United States with the poorest air quality.
Beginning in the late 20th century, coordinated efforts between local agencies, industry, and federal regulators led to substantial reductions in air pollution. These improvements were achieved through modernization of industrial processes, implementation of emission controls, and strengthened environmental regulations.
While air quality has improved significantly, continued monitoring remains necessary to maintain compliance and protect public health.
EPA National Ambient Air Quality Standards (NAAQS)
The Bureau’s monitoring program focuses on the following criteria pollutants:
Fine Particulate Matter (PM2.5)
PM2.5 consists of airborne particles with aerodynamic diameters less than or equal to 2.5 micrometers. These particles may be emitted directly or formed through atmospheric chemical reactions.
- Annual standard: 9 µg/m³
- 24-hour standard: 35 µg/m³
Ozone (O₃)
Ground-level ozone is a secondary pollutant formed through photochemical reactions involving nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) in the presence of sunlight.
- 8-hour standard: 70 parts per billion (ppb)
These standards are established by the EPA based on scientific and epidemiological studies demonstrating adverse health effects associated with elevated exposure.
Monitoring Objectives
The air quality monitoring program is designed to:
- Assess compliance with federal ambient air quality standards
- Provide accurate and timely data on pollutant concentrations
- Evaluate long-term trends in air quality conditions
- Support public health protection and regulatory decision-making
- Inform mitigation and environmental planning efforts
Public Health and Environmental Significance
PM2.5 and ground-level ozone are associated with a range of adverse health outcomes, particularly among sensitive populations including children, older adults, and individuals with respiratory or cardiovascular conditions.
Continuous monitoring provides critical data to support early identification of elevated pollution levels and to guide appropriate public health responses when necessary.
Commitment to Air Quality Protection
The Bureau remains committed to maintaining and improving air quality in Chattanooga–Hamilton County through consistent monitoring, data evaluation, and coordination with local and federal environmental partners.
Ongoing efforts are directed toward sustaining compliance with national air quality standards and protecting the health and welfare of residents.
What Are Criteria Pollutants?
Criteria pollutants are a group of common air pollutants regulated by the U.S. Environmental Protection Agency (EPA) because they are known to be harmful to human health and the environment.
They are called “criteria” pollutants because the EPA sets National Ambient Air Quality Standards (NAAQS) for them based on scientific criteria (health and environmental research).
The six criteria pollutants are:
- Particulate Matter (PM2.5 and PM10) – tiny particles that can be inhaled into the lungs; linked to respiratory and cardiovascular effects
- Ozone (O₃) – a gas formed in the atmosphere from chemical reactions involving sunlight and emissions from vehicles and industry
- Carbon Monoxide (CO) – a colorless gas produced by incomplete combustion, primarily from motor vehicles
- Sulfur Dioxide (SO₂) – mainly from burning fossil fuels at power plants and industrial facilities
- Nitrogen Dioxide (NO₂) – produced from combustion processes such as traffic and power generation
- Lead (Pb) – historically from gasoline and industrial sources; now greatly reduced but still monitored due to toxicity
Why they matter:
These pollutants are tracked nationwide because they:
- can affect breathing and lung function
- contribute to heart and lung disease
- reduce visibility (haze/smog)
- damage ecosystems, crops, and infrastructure
The EPA sets limits for each pollutant under the NAAQS program to protect public health, including sensitive groups such as children, older adults, and people with asthma or heart conditions.
Air Quality and Airborne Biological Particles in Chattanooga–Hamilton County
Overview
Air pollution does not consist entirely of man-made substances. In addition to emissions from transportation, industry, and other human activities, many pollutants are released directly from natural sources, including plants, trees, and fungi.
These naturally occurring pollutants include pollen and mold spores, which are commonly present in the outdoor environment. While natural in origin, they can still affect air quality and public health, particularly for sensitive individuals.
Airborne Biological Particles and Public Health
Pollen and mold spores are classified as airborne biological particles, referring to naturally occurring microscopic materials suspended in the air that can trigger allergic reactions.
Exposure to elevated levels of airborne biological particles may result in symptoms including:
- Itchy, watery eyes
- Sneezing
- Nasal congestion
- Wheezing or respiratory irritation
Individuals with asthma, seasonal allergies, or other respiratory conditions may experience increased sensitivity during periods of elevated concentrations.
Air Quality Monitoring Context
Although airborne biological particles are not regulated under the EPA National Ambient Air Quality Standards (NAAQS), they are an important component of overall environmental conditions. Their presence can contribute to perceived air quality impacts and may coincide with periods of elevated ozone or particulate matter levels.
The Bureau continues to monitor a range of air quality indicators to provide a comprehensive understanding of environmental conditions affecting Chattanooga–Hamilton County residents.
Integrated Environmental Awareness
Understanding air quality requires consideration of both man-made and natural contributors. While regulatory programs focus on criteria pollutants such as PM2.5 and ozone, naturally occurring substances such as pollen and mold spores also play a significant role in respiratory health outcomes.
Ongoing monitoring and public awareness efforts help ensure that residents have access to timely and relevant air quality information throughout the year.