The correct answer is option 2: ozone concentration. Chronic obstructive pulmonary disease (COPD) refers to a group of lung diseases that block airflow and make it difficult to breathe. Ozone, which is a gas made up of three oxygen atoms, is a major component of air pollution. High levels of ozone can be harmful to human health, particularly to the respiratory system.

Option 1, solar radiation, is not the correct answer because while excessive exposure to solar radiation can cause skin damage and increase the risk of skin cancer, it does not directly cause COPD.

Option 3, nitrogen oxide, is not the correct answer as well. While nitrogen oxide emissions from vehicles and industrial processes can contribute to air pollution and respiratory problems, it is not a direct cause of COPD.

Option 4, particulate pollutant, is also not the correct answer. Particulate pollutants, such as fine dust, smoke, and soot, can cause respiratory issues and worsen existing respiratory conditions, but they are not the primary cause of COPD.

Therefore, option 2, ozone concentration, is the correct answer as high levels of ozone in the air can contribute to the development and exacerbation of COPD.