Frequently Asked Questions


  1. How accurately can PlumePGH tell me how much pollution I’m exposed to every day?
  2. What is the severity of pollution far from the source?
  3. Which sources are shown and why?
  4. How can I see pollution plumes from pollution sources not currently mapped?
  5. Why are there missing days from the calendar line?

1. How accurately can PlumePGH tell me how much pollution I’m exposed to every day?

All of the variability in exposure shown by PlumePGH is due to air inversions and wind patterns, which are powerful determinants of pollution exposure in our region. The modeled emission volume from each facility matches annual average emissions as declared in the self-reported air emissions inventory. Actual emissions from these facilities do change over time due to a number of unplanned and planned causes, and is an important component of pollution exposure variability, but facilities do not share hourly or daily emissions levels, and PlumePGH is not yet capable of determining these independently.

2. What is the severity of pollution far from the source?

NOAA's modern High-Resolution Rapid Refresh (HRRR) weather model underpins much of weather forecasting in the United States, and it shows pollution traveling close to the ground many miles distance, especially during times of inversion.

Beyond NOAA's HRRR model, we see pollution impacts at a distance from pollution monitoring data. One example is evidence of Clairton Coke Works' pollution impacting South Fayette, 16 miles away.

For more details, see Pollution Carries.

3. Which sources are shown and why?

Our model shows the four largest emitters of SO2 and other sulfur oxides in Allegheny County, which correlates strongly with smell reports and also health impacts. See the self-reported air emissions inventory for these four sources. In 2018, these four sources produced 99% of all declared Sulfur oxides in the Allegheny County emissions inventory, 99% of Polycyclic Aromatic Hydrocarbons, and 67% of all PM2.5 declared in the same inventory. There are a number of smaller pollution sources not shown that can also correlate with smell reports and monitor values and impact health.

4. How can I see pollution plumes from pollution sources not currently mapped?

The PlumePGH team can set up a custom plume visualization for an additional source, subject to limited developer capacity. Feel free to Contact Us.

5. Why are there missing days from the calendar line?

While yearly improvements in NOAA's High-Resolution Rapid Refresh (HRRR) weather model are largely responsible for increasingly accurate weather forecasting in the United States, it's still not 100% accurate. We find that for around 10% of days, plumes predicted by the weather models do not accurately line up with smell reports and monitor values. Before publishing a day's plume model, we perform a quality assurance analysis and will omit a day if it does not appear to be accurate.