The city of Pittsburgh had the worst air quality in the United States on Thursday, Jan. 23. That statistic was reported by AirNow, a website that the government uses to track the air quality of the entire country.

According to the site, on Jan. 23, the Air Quality Index (AQI) for the Liberty-Clairton area was 159, which is considered unhealthy by the Environmental Protection Agency (EPA). For comparison, Beijing, China, which is considered to have some of the worst air on the planet, had an AQI of 184, according to AQICN.org, a website dedicated to tracking the air quality of major cities in China.

According to AirNow.gov, a website run by the EPA, when Air Quality is unhealthy, “everyone may begin to experience health effects” and “members of sensitive groups may experience more serious health effects.” Sensitive groups include people with lung disease, children, older adults and people who are more active outside than others.

The EPA states that high AQI can cause irritation to the eyes and lungs. It also damages and inflames the cells that line the lungs, and can cause permanent lung damage. It can cause asthma and typically aggravates asthma in people who already have the condition, often to the point of needing medical attention.

Unhealthy air quality isn’t a new issue for Pittsburgh, it’s been a problem for almost a century. By the 1940s, Pittsburgh’s air was so polluted that the sky appeared black from coal pollution almost all the time. In 1941 Pittsburgh passed laws intended to fix air pollution, and while these laws brought clear improvements, they still aren’t perfect.

This all comes from the back of a controversial essay recently written by a Google employee entitled “When better isn’t good enough: Why I tell my Google co-workers and industry peers to avoid Pittsburgh.” The essay, which was published in PublicSource, a non-profit newsroom based in Pittsburgh, details Dennis Towne, a Google employee and his experiences with Pittsburgh’s air since moving to the city. Towne writes “an obnoxious stench in the mornings, a mix of smells resembling coal tar and sulfur” as well as waking up “in the middle of the night to a stench that burns the lungs and turns the stomach.”

Google issued a response to the statement, in which they made clear that the views of this employee are not the views of the company, and that they remain clear to the public that Google remains committed to Pittsburgh. At the same time, Google acknowledged their commitment to provide the local government with technological innovations to improve the air quality.

Allegheny County Executive Rich Fitzgerald seems even less concerned by the article. “For people that have lived here and grown up here, they realize it’s way better, way better than it’s ever been and continues to get better,” Fitzgerald said when asked about the essay. Fitzgerald also notes that sulfur dioxide has dropped by 88 percent, however this reduction is not felt by the entire city of Pittsburgh. Specifically, the air near Clairton Coke Works has only improved 27 percent.

Since Pittsburgh’s population is under 350,000 people, the local government is not required to notify the public of the daily AQI. People looking to find the AQI can view the current air quality status and a weekly forecast on AirNow.gov. Several mobile phone apps are available, such as Air Quality | Air Visual, which offers current AQI, and forecasts for around the world. Another app is Smell PGH, which is dedicated to tracking the AQI as well as the smell of pollutants for various areas in Pittsburgh.