Pulmonary toxicity studies are preclinical studies that are conducted to evaluate the potential adverse effects of a substance on the respiratory system, including the lungs and airways. These studies are typically conducted in laboratory animals, such as rats, mice, or dogs, to assess the safety of a drug or other substance before testing in humans.

The primary objective of pulmonary toxicity studies is to identify any potential adverse effects of the substance on respiratory function, including changes in lung function, respiratory rate, and histopathological changes in lung tissue. These studies can include a range of endpoints, such as pulmonary function testing, histopathological examination of lung tissue, and assessment of inflammation and oxidative stress in lung tissue.

Pulmonary toxicity studies can be further classified based on the exposure period and the endpoints evaluated:

1. Acute pulmonary toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the respiratory system after short-term exposure, usually for a few days to a few weeks.
2. Sub-chronic pulmonary toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the respiratory system after repeated exposure over a period of several weeks to several months.
3. Chronic pulmonary toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the respiratory system after repeated exposure over a period of several months to several years.

The results of pulmonary toxicity studies can help identify any potential adverse effects of the substance on the respiratory system, and can help inform decisions about the safety of the substance for use in humans. These studies are an important part of the preclinical safety assessment of drugs and other substances, particularly those intended for long-term use or for use in populations with a higher risk of respiratory toxicity.