What is the most heavily used toxic pollutant in leather tanning?

The most heavily used toxic pollutant in leather tanning is chromium. This metal, particularly in its trivalent form (Cr(III)), is widely utilized in the tanning process because it effectively preserves animal hides, resulting in durable and flexible leather. When properly managed in manufacturing, chromium can be contained and used safely; however, its use poses significant environmental and health risks if not handled with care.

Chromium in its hexavalent form (Cr(VI)) is especially dangerous, being highly toxic and a known carcinogen. The tanning process can lead to contamination of soil and water if wastewater containing chromium is improperly disposed of, contributing to serious environmental pollution. Thus, while other metals like arsenic, lead, and copper are associated with various environmental and health issues, chromium's widespread use and potential for hazardous impact make it the most significant toxic pollutant in this industry.