AUSTIN (KXAN) — Over the last few days you may have noticed a change in the air. Gone is the perfect blue sky in between the clouds. Instead, visibility isn’t perfect when looking at distant objects or buildings and there’s a thickness to the air that you can almost taste.
Check out how Austin looked from The Domain (see image below), you could barely see the sky scrapers Saturday afternoon.
You can blame two things for this: Humidity and particulate pollution.
The humidity has been tropical with dew points in the 70s making even the early mornings feel uncomfortable. The relative humidity has ranged from 60-90%+ depending on the time of day. This level of humidity in the air isn’t just felt, but you can see the suspended water vapor, which accounts for some of the lowered visibility.
Fine particulate matter pollution
Adding to the lower visibility are a type of pollution known as fine particulates. Specifically this week PM2.5 is the primary pollutant here in Central Texas.
PM2.5 means fine particulate matter pollutants with a diameter at or below 2.5 micrometers in size. A human hair is about 50 to 70 micrometers in diameter.
How do these particulates form? The EPA says “most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles.” Sulfate aerosols are closer to 0.1 micrometers in diameter.
But if they’re so small how can we see them?
According to NOAA, when the relative humidity is above 60% these fine particulates absorb water in the air and grow in size. The higher the relative humidity, the bigger the droplets.
These bigger, but still tiny droplets, when in high concentrations, can lower visibility and create a haze in the lower levels of the atmosphere. This is caused by the tiny droplets absorbing and scattering the light before it reaches you.
Should I worry about my health?
The level of PM2.5 this week in the Austin Metro is expected to stay in the “Moderate” category according to Airnow.gov. Only people who are unusually sensitive to particulate pollution should ease off the exercise and reduce time outside.
For the rest of us, the high humidity and heat will just make you sweaty and thirsty, but will also tire you out more quickly too.