Question: what is the odor threshold for hydrogen sulfide
[{'answer': '0.00047 ppm or 0.47 ppb', 'provenance': [{'wikipedia_id': '154738', 'title': 'Hydrogen sulfide', 'start_paragraph_id': 59, 'start_character': 12, 'end_paragraph_id': 59, 'end_character': 35, 'bleu_score': 1.0, 'section': 'Section::::Safety.:Toxicity.\n'}]}]