[Original article in Spanish. Title translation, and following summary of the article's key points, provided by Business & Human Rights Resource Centre.] The river Matanza-Riachuelo has been the most polluted for more than a century, but in the last decades the contamination has turned critical. On April, the National Audit Office (Auditoría General de la Nación) warned of a "health catastrophe" and the national obdusman alerted twice on the lack of public policies about this issue. The river could start to be cleaned up due to an innovative ruling of the Supreme Court of Justice which is already considered a landmark of Latinamerican environmental law. In response to a lawsuit from local people affected by the contamination, the court ordered 44 companies to report on the discharges they throw to the river - among them are Shell & Mercedes Benz. It also ordered the state to draft a management plan. Around the river, more than 3.5 million people live and more than 3500 companies operate.