Step 1: Identify the link between tanning and chromium.
Chromium, particularly hexavalent chromium, is extensively used in the leather tanning process. Improper disposal of tannery effluent is a major source of chromium contamination in soil and water.
Step 2: Identify major leather tanning hubs in India.
India has several major centers for the leather industry. The most prominent are Kanpur in Uttar Pradesh and a large cluster in Tamil Nadu (including cities like Vellore, Ambur, and Dindigul).
Step 3: Evaluate the states known for pollution from this industry.
While Kanpur (Uttar Pradesh) is also heavily polluted, the state of Tamil Nadu has a massive concentration of tanneries and a long-documented history of severe and widespread chromium pollution in the Palar river basin, making it the most cited example for this specific environmental issue in India.