Final answer:
Chronic respiratory diseases, allergies, and certain types of cancers can be linked to decreases in environmental quality.
Step-by-step explanation:
The medical conditions that can be linked to decreases in environmental quality include chronic respiratory diseases such as asthma, bronchitis, and emphysema, as well as allergies and certain types of cancers. Mental illness, although not directly linked to environmental quality, can be influenced by factors like air pollution. Inflammatory bowel disease, on the other hand, is not typically associated with decreases in environmental quality.