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

In the leather tanning process, chromium is the most heavily used toxic pollutant. Chromium salts, particularly chromium(III) sulfate, are essential for tanning hides, as they provide strength and durability to the final leather products. The use of chromium in tanning helps in preserving the hides and giving them their desired texture and finish.

However, while chromium(III) is less toxic, the concern arises with chromium(VI), a more hazardous form that can be produced during the tanning process or as a byproduct. This chromium(VI) can have serious health implications, including respiratory issues and skin irritation, making it a significant environmental and health concern in the leather industry.

The other options are also toxic pollutants but are not used as extensively in leather tanning. Arsenic, while toxic, is not commonplace in tanning processes. Lead and cadmium have their own associated health risks and are regulated substances, but they don’t play a primary role in leather tanning compared to chromium.