Question: what did the clean air act allow citizens to do that no previous u.s. environmental law had allowed
[{'answer': 'citizen suits .', 'provenance': [{'wikipedia_id': '19060778', 'title': 'Clean Air Act (United States)', 'start_paragraph_id': 5, 'start_character': 104, 'end_paragraph_id': 5, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19060778', 'title': 'Clean Air Act (United States)', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 283, 'bleu_score': 0.953991849837532, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2423291901607251828}, 'section': 'Section::::Abstract.'}]}]