A Code Orange air quality alert has been issued for thousands on Tuesday due to high levels of air pollution.

The alert covers the Liberty and Clairton area in Pennsylvania, including Clairton, Glassport, Lincoln and Port Vue, as well as the Susquehanna Valley, including Dauphin, Lebanon, Cumberland, York and Lancaster counties.

The Pennsylvania Department of Environmental Protection (DEP) warned that pollution levels may become unhealthy for sensitive groups, including children, the elderly, and people with asthma, heart disease, or other lung conditions. 

Those in these groups are advised to avoid outdoor exercise or strenuous activity, as even brief exposure can cause coughing, shortness of breath, chest discomfort or eye and throat irritation.

The poor air quality is caused by elevated fine particulate matter (PM2.5) trapped near the ground by a combination of light winds, snow cover, and morning temperature inversions, which prevent pollutants from dispersing. 

National Weather Service (NWS) forecaster David Martin explained that these inversions occur when a layer of warm air sits above cooler air at ground level, keeping smoke, haze, and other pollutants stagnant.

The alert is expected to remain in effect throughout the day, and officials urge residents to stay informed, limit outdoor activities, and take protective measures, such as keeping windows closed or using air purifiers indoors. 

While the general population may not be severely affected, caution is essential for those most at risk.

The Air Quality Index (AQI) uses a color-coded system to communicate the potential health risks of air pollution. 

Green indicates that air quality is satisfactory and poses little or no risk. Yellow means air quality is generally acceptable, but some individuals who are unusually sensitive to pollution may be affected. 

An orange level signals that members of sensitive groups, such as children, the elderly, or those with respiratory or heart conditions, may experience health effects, while the general public is less likely to be impacted. 

Red indicates that some people in the general population may experience health effects, and sensitive groups may face more serious consequences. 

A purple rating is a health alert, meaning the risk of adverse effects is increased for everyone. The most severe level, maroon, is a health warning of emergency conditions, with everyone more likely to be affected. 

A study released last month showed exposure to toxic pollutants may increase the risk of developing devastating neurological conditions, a study suggests.

Researchers in Sweden evaluated 1,000 patients diagnosed with amyotrophic lateral sclerosis (ALS), a terminal neurodegenerative disease that attacks neurons in the brain and spinal cord responsible for motor functions.

Also called Lou Gehrig's disease and motor neuron disease in the UK, ALS affects about 30,000 Americans and kills in just two to five years as the neuron damage attacks the body's ability to move, eat and breathe. About 5,000 die every year.

The causes are largely unknown, but recent research suggests environmental contaminants could lead to inflammation that attacks neurons in the brain and spinal cord.

In the new study, researchers compared ALS patients both to siblings and healthy controls and tracked their exposure over 10 years to the pollutants PM2.5, PM10 and nitrogen dioxide.

PM2.5 are a group of microscopic particles that are emitted directly into the air from fossils fuels burned from factories and gasoline-powered stoves and cars, as well as burning wood in fireplaces. These can penetrate deep into the lungs and bloodstream, while PM10, which includes dust and pollen, infiltrates the airways.

Nitrogen dioxide, meanwhile, is a gas that comes from burning fossil fuels.

The team found exposure to even small amounts of pollutants over the course of 10 years increased the risk of developing ALS by up to 30 percent. Additionally, the likelihood of the disease progressing more quickly went up by 34 percent.