Section 243.104  Nondegradation

Existing ambient air quality which is better than the extablished ambient air quality standards at the date of their adoption will be maintained in its present high quality.  Such ambient air quality shall not be lowered unless and until it is proved to the Illinois Environmental Protection Agency (Agency) that such change is justifiable as a result of necessary economic and social development and will not interfere with or become injurious to human health or welfare.