Carbon monoxide (CO) is a colorless, odorless gas that when inhaled at high levels can cause headaches, nausea, dizziness and vomiting. Repeated exposure over long periods can lead to heart disease.

Breathing in environments with high levels of nitrogen dioxide (NO2) can increase the risk of respiratory problems. Common symptoms are coughing and difficulty breathing. More serious health problems such as respiratory infections may occur if exposed for longer periods.

Ground-level ozone can worsen existing respiratory diseases and can also lead to throat irritation, headaches and chest pain.

Particulate matter pollution consists of particles with a diameter less than 10 micrometers. Particles larger than 2.5 micrometers can accumulate in airways, causing many health problems. If exposed frequently, it can lead to eye and throat irritation, coughing or difficulty breathing as well as worsening asthma. Excessive and frequent exposure can lead to many serious health impacts.

Particulate matter pollution consists of particles with a diameter less than 2.5 micrometers that can penetrate into the lungs and bloodstream, causing many serious health problems. The most serious impacts are on the lungs and heart. If exposed, it can lead to coughing or difficulty breathing, worsen asthma and cause chronic respiratory diseases.

Exposure to sulfur dioxide (SO2) can lead to eye and throat irritation while worsening asthma and chronic bronchitis.