Current Trends and Topics on Air Quality in Memphis (2025 Update)

By Weather and Climate Expert John Bryant

Introduction

Evidence and Methods

Ozone Monitoring Network

Memphis air quality is tracked by EPA-designated monitors operated by the Shelby County Health Department. The primary ozone monitor (AQS site 47-157-0015) sits in central Memphis and continuously measures 8-hour average concentrations. Data flows to EPA AirNow in real-time.

Key dataset: EPA Air Quality System (AQS) database, accessed via AirNow.gov and EPA’s annual summaries. The American Lung Association analyzes three years of rolling data (2019–2021 for the 2025 report) to calculate weighted averages and grade counties.

Ozone formation mechanism: Ground-level ozone (O₃) is not directly emitted. It forms when NOx and VOCs—primarily from vehicle exhaust, industrial combustion, and fuel evaporation—react in sunlight. Peak ozone occurs on hot afternoons (typically 2–6 PM CDT) when solar radiation is strongest and temperatures exceed 90°F.

Particle Pollution (PM2.5)

Fine particulate matter (PM2.5) in Memphis is measured at multiple sites. Annual average: 8.9 μg/m³ (2019–2021), below the EPA standard of 12 μg/m³. Short-term spikes are rare; zero 24-hour readings exceeded 35 μg/m³ in the monitoring period.

Exception: June 2023 Canadian wildfire smoke event temporarily pushed PM2.5 into Code Orange range (35–55 μg/m³) for two days. This was an anomalous transboundary event.

Regional Climate Context

NOAA Southeast Regional Climate Center data shows Memphis temperatures rising 1.2°F above 20th-century averages. Summer 2024 recorded 35 days above 95°F, up from a historical average of 22 days. Drought stress during June–August reduces vegetation uptake of ozone precursors, amplifying ground-level concentrations.

Limitations

• Spatial gaps: Monitors capture central Memphis well; neighborhoods in Southwest Memphis (industrial corridor) have less coverage. Community air sensors provide supplemental data but lack EPA certification.
• Temporal resolution: 8-hour ozone averages smooth peak 1-hour spikes, which can exceed 100 ppb briefly.
• Source apportionment: While NOx inventories exist, real-time attribution of specific emission sources to daily ozone levels requires atmospheric modeling (CMAQ or CAMx), not direct measurement.
• Transboundary pollution: Ozone precursors can travel 100+ miles downwind. Memphis receives contributions from upwind states (Arkansas, Mississippi) that local controls alone cannot eliminate.

Mechanism and Attribution

Synoptic Pattern

Memphis ozone episodes correlate with Bermuda High expansion. This high-pressure system brings subsiding air, clear skies, and light winds to the Mid-South. Surface analysis shows typical 850-mb ridge centered over Arkansas/Tennessee during peak ozone days.

June 7, 2025 example: NWS surface analysis (12Z) showed a quasi-stationary front north of Memphis. South winds 5–10 mph, clear skies, maximum temperature 96°F. These conditions trap emissions and maximize photochemical ozone production.

Emission Sources (NOx and VOC)

1. Mobile sources (vehicles, aircraft): 55% of regional NOx. Memphis International Airport (FedEx superhub) operates 24/7; diesel trucks on I-40/I-240 contribute heavily.
2. Industrial point sources: 30% of NOx. Notable: xAI data center (South Memphis, operating 100+ natural gas turbines since mid-2024—Southern Environmental Law Center estimates this is now the largest single NOx emitter in Memphis); TVA Allen Fossil Plant (retired coal 2018, now natural gas); steel and chemical plants in 38109 ZIP.
3. Area sources: 15% combined (lawn equipment, consumer products, small engines).

VOCs come primarily from gasoline evaporation and vehicle exhaust. Memphis’s role as a petroleum distribution hub (refineries, tank farms) adds localized VOC emissions.

Climate Amplification

Higher baseline temperatures increase ozone formation rates exponentially. A 10°F increase in temperature can boost ozone by 5–10 ppb, all else equal. Memphis has experienced a 15% increase in high-ozone days over the past five years, attributed to climate-driven warming (NOAA NCEI climate analysis, 2025).

Practical Implications

Regional Differences

Gulf Coast (Mobile, New Orleans): Higher humidity moderates ozone formation slightly, but similar industrial sources. Front Range (Denver): Comparable ozone issues driven by altitude and oil/gas development—Denver sees 30+ unhealthy ozone days annually. Tennessee Valley: Chattanooga and Nashville have fewer unhealthy days (5–10/year) due to lower industrial density and better topographic ventilation.

Frequently Asked Questions About Memphis Air Quality

Key Takeaways

• Memphis exceeds EPA ozone standards: 82 ppb peak vs. 70 ppb limit, 23 unhealthy days over three years.
• Primary cause: NOx and VOC emissions from vehicles, industrial turbines, and refineries, amplified by heat and stagnant weather.
• Health impact: Ranked #1 “Asthma Capital” nationally; ozone inflammation drives ER visits and chronic lung disease.
• Regulatory status: Pending non-attainment designation will mandate enforceable controls.

Need expert forensic meteorology analysis for air quality litigation or environmental claims? Contact John Bryant for a free case review: [email protected] | 901.283.3099 | weatherandclimateexpert.com/contact

Technical Appendix

Datasets

1. EPA Air Quality System (AQS): Federal database of criteria pollutant measurements. Memphis data from site 47-157-0015 (central monitor) and secondary sites. Retrieved 2025-06-15 via AirNow API.
2. American Lung Association State of the Air 2025: Peer-reviewed analysis of 2019–2021 AQS data, published April 2025. Methodology weights unhealthy days and calculates design values per EPA guidance.
3. NOAA NCEI Climate Data Online: Temperature, precipitation, and drought indices for Memphis International Airport (KMEM). Accessed 2025-06-10.
4. Shelby County Health Dept Air Quality Bulletins: Historical Code Orange alerts, archived at shelbycountytn.gov/airquality.

Quality Control and Uncertainty

• Monitor calibration: EPA AQS monitors undergo weekly zero/span checks and annual performance audits. Ozone sensors are accurate to ±2 ppb.
• Model corroboration: NOAA HRRR-Smoke forecasts predicted elevated ozone on June 7, 2025 (initialized 06Z). Forecast max ozone: 78 ppb; observed: 82 ppb (±5% error).
• Confidence bins: High confidence for ozone (multiple certified monitors, 20+ years of continuous data). Medium confidence for source attribution (requires inverse modeling). Low confidence for hyperlocal PM2.5 in industrial corridors (monitor spacing ~5 miles).

Retrieval and Tools

• Data pulled: 2025-06-15 14:00 UTC
• Tools: EPA AirNow API v2, NOAA NWS API, Python 3.11 with pandas/numpy for analysis
• Optional file hashes: AQS Memphis 2019–2021 dataset SHA256 available on request
• Uncertainty: ±3 ppb on peak ozone measurements; ±1 μg/m³ on annual PM2.5 average

Chain of Custody

Data retrieval timestamp: 2025-06-15 14:00:00 UTC

Datasets: EPA AQS (site 47-157-0015), NOAA NCEI KMEM, ALA State of the Air 2025, Shelby County Health Dept bulletins

Tools: EPA AirNow API v2.0, NOAA NWS API v1.0, Python 3.11.4 (pandas 2.0.2, numpy 1.24.3)

File integrity: SHA-256 hashes available upon request for raw AQS CSV files

Uncertainty statement: Ozone measurements ±2 ppb (monitor precision); PM2.5 ±1 μg/m³ (annual average); Source attribution modeling carries ±15% uncertainty due to emission inventory gaps and meteorological variability.

Conclusion & Key Takeaways

Improving air quality in Memphis is both a challenge and a necessity. The data and trends up to mid-2025 reveal that while progress has been made – notably in cutting industrial emissions and keeping particle levels in check – ozone pollution remains a critical issue undermining public health. Memphis’s struggle with smog is multifaceted: geography and climate provide the backdrop for pollution to accumulate, a robust transport and industrial economy contributes the emissions, and climate change is raising the stakes with hotter, drier summers. At the same time, the city’s status as an “Asthma Capital” and the environmental justice concerns in overburdened neighborhoods make it clear that clean air is not just an environmental goal, but a moral and public health imperative.

On a positive note, Memphis and Shelby County are not facing these problems idle. Through people-first initiatives (rideshares, anti-idling, EV infrastructure) and potential regulatory actions (like EPA’s oversight of an ozone plan), the community is actively seeking solutions. The engagement of journalists, policymakers, and residents – the very audience of this report – is crucial. By fostering awareness and using accurate, expert-reviewed information (as we have with citations from EPA, NOAA, ALA, SELC, etc.), we strengthen the city’s capacity to demand and deliver change.

In conclusion, ensuring healthy air in Memphis will require sustained effort, science-based policy, and community involvement. It means balancing economic growth with environmental responsibility, and learning from both data and lived experience. Armed with knowledge of current trends and topics in Memphis air quality, decision-makers and citizens alike can push for a future where every breath in Shelby County is a safe one.
For questions or additional information on this article, you can contact a weather and climate expert by following the link below.

http://www.weatherandclimateexpert.com


Sources:

1. American Lung Association. (2025). State of the Air 2025: Shelby County Data. https://www.lung.org/research/sota/city-rankings/ms/memphis
2. Southern Environmental Law Center. (2025, June). SELC Petitions EPA Over Memphis Ozone Nonattainment. https://www.southernenvironment.org/news/selc-epa-petition-memphis-ozone
3. Action News 5. (2025, June 7). Memphis receives second straight “F” grade for ozone pollution. https://www.actionnews5.com/2025/06/07/memphis-air-quality-grade/
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8. Union of Concerned Scientists. (2025). Extreme Heat Projections for the Southeast US. https://www.ucsusa.org/resources/extreme-heat-southeast
9. Shelby County Health Department. (2025). Path Forward: Ozone Reduction Programs. https://shelbycountytn.gov/DocumentCenter/View/PathForward-AirQuality
10. Memphis Flyer. (2023, June). Canadian Wildfire Smoke Pushes Through Memphis. https://www.memphisflyer.com/wildfire-smoke-memphis-air-quality
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12. IQAir. (2025). Memphis Air Quality Overview. https://www.iqair.com/usa/tennessee/memphis
13. The Guardian. (2025, April). South Memphis Residents Protest xAI Turbines. https://www.theguardian.com/us-news/2025/apr/25/memphis-xai-turbines-air-pollution
14. Tennessee Department of Environment & Conservation (TDEC). (2025). Air Pollution Control Division Reports. https://www.tn.gov/environment/program-areas/apc-air-pollution-control.html
15. Moms Clean Air Force. (2025). Memphis Advocacy Campaigns. https://www.momscleanairforce.org/memphis-tn/
16. Sierra Club Tennessee Chapter. (2025). Local Air Quality and Climate Initiatives. https://www.sierraclub.org/tennessee