Monitored Data
Data Removal
As part of the quality assessment and quality control process, it has been determined that the monitoring equipment at the Liberty Monitoring Station was not fully functional between March 20, 2024 and May 14, 2024 and on May 17, 2024. This may have resulted in inaccurate data. The data from this time period is being invalidated by the ACHD. Please see the FAQs for further details on this occurrence.
Air Quality operates an extensive network of air monitoring equipment throughout the county.
This network collects information on a variety of pollutants, including criteria pollutants and hazardous air pollutants (HAPs).
Hourly Data
View the Key to Air Quality Data(PDF, 107KB).
This hourly data is unverified. It is automatically generated by our network of air monitoring stations and is not considered official until it is reviewed by qualified members of our staff. Sometimes, an electrical disruption or equipment malfunction can result in erroneous data.
Note: On April 15, 2022, the Allegheny County Health Department learned that for the second year in a row, the county has met federal air quality standards for fine particulate matter (PM2.5) at all eight air quality monitors. This table shows the highest air quality concentrations recorded(PDF, 67KB) at any site over the most recent three years (based on maximum three-year averages), given by pollutant and averaging duration.
We carefully monitor our equipment; however, unusual or worrisome data can be reported by calling 412-687-ACHD (2243).
Air Quality Annual Reports
Each year, all of our verified data is collected and analyzed as part of our Air Quality Report. You can view all of our Annual Reports on our Air Quality Reports and Studies page.
About the Pollutants We Track
Criteria Pollutants
The Environmental Protection Agency (EPA) has identified six common air pollutants that are important to measure and track. These are known as "Criteria Pollutants". They are:
- Particle pollution
- Ozone
- Carbon monoxide
- Sulfur dioxide
- Nitrogen oxides
- Lead
Because these pollutants can harm human health and the environment, the EPA has set science-based guidelines for how much of each pollutant should be in the air. These limits, known as National Ambient Air Quality Standards (NAAQS), are designed to help avoid pollution concentrations that could adversely affect our health.
Hazardous Air Pollutants
Also known as air toxics, hazardous air pollutants (HAPs) are pollutants that are known or suspected to cause cancer or other serious health effects. Examples of toxic air pollutants include:
- Benzene
- Perchlorethlyene
- Methylene chloride
- Dioxin
- Asbestos
- Toluene
- Cadmium
- Mercury
- Chromium
- Lead compounds
The EPA has designated 187 hazardous air pollutants. To see the full list, visit the EPA website.
Most HAPs originate from human-made sources, including mobile sources (e.g., cars, trucks, buses) and stationary sources (e.g., factories, refineries, power plants), as well as indoor sources (e.g., some building materials and cleaning solvents). Some HAPs are released from natural sources such as volcanic eruptions and forest fires.
National Emission Standards for Hazardous Air Pollutants (NESHAPs) are EPA set emission limits for air toxics. The standards for a particular type of source (such as dry cleaners or gasoline stations) are known as the Maximum Achievable Control Technology (MACT). Standards for air toxics are authorized under the Clean Air Act, section 112.
ACHD Article XXI §2104.08(PDF, 2MB) PA rules on air toxics including any additions or changes made by the EPA.
In addition, the ACHD's Air Quality program has protocols in place to help regulate and control these toxic air pollutants, as well as respond to new data concerning air toxic “hotspots” and areas of interest.
Our Air Toxic Guidelines, which are followed by the ACHD permit engineers when issuing air permits for new and existing sources of air toxics in Allegheny County, were originally developed in 1988 and have recently been revised by the ACHD.
Data Removal FAQ
What caused the monitor issues?
The monitoring issue was caused by a probe line that became dislodged from its exterior housing on the sulfur dioxide monitor. This caused the ambient sulfur dioxide readings to become lower than normal despite the instrument passing all regular quality assurance checks. Hydrogen sulfide concentrations in this setup require two independent sulfur dioxide monitors to operate in together. The hydrogen sulfide data was also affected.
Does this impact any enforcement actions?
No current enforcement actions are impacted by this. However, the specific data affected during this time period will not be used in any future enforcement action(s).
Is there a backup with which to understand any data for these sources during this period?
Only sulfur dioxide and hydrogen sulfide data were affected during this time period. The second sulfur dioxide monitor which measures hydrogen sulfide and sulfur dioxide was unaffected and those data can still be evaluated. However, without the other monitored data it cannot be known what percentage of the total concentration in the air at that time period was hydrogen sulfide or sulfur dioxide. All other monitored data at the Liberty monitoring station operated normally and can be used to evaluate ambient air quality conditions during this time period.
How can the public be sure that any data that the ACHD is collecting is legitimate and that monitors were not impacted?
In order to inform the public of real-time air quality conditions, the ACHD posts hourly data generated by automated instruments that is not considered official and valid until fully reviewed by qualified Air Quality program staff members. Monitored data at the ACHD goes through a thorough quality assurance and quality control (QA/QC) system where instruments are regularly checked against United State Environmental Protection Agency (EPA) and National Institute of Standards and Technology (NIST) standards. In this instance, this same system identified the issue and invalidated the data while monitoring technicians repaired the damaged infrastructure.
In addition to multiple levels of internal and independent QA/QC, the monitors at the ACHD air monitoring network are audited by the EPA at regular intervals through the National Performance Audit Program (NPAP) and National PM2.5 Performance Evaluation Plan (PEP). The dislodged probe line was a unique situation that has never been encountered before at any of the ACHD’s air monitoring stations.
What is ACHDs plan for fixing the impacted monitors?
The monitoring systems were diagnosed and fixed within days of identifying the issue. After that, the monitored data resembled historical data trends at the site.
How will the ACHD ensure they are maintained in working order moving forward?
The ACHD has increased the frequency of station infrastructure inspection by the monitoring technicians who regularly visit the stations. Recent upgrades to the ACHD’s air monitoring database will allow for an expansion of automated routines to identify inconsistent data more quickly.