Mercury Blocks Sulfur Pathways Mercury’s toxicity is often underestimated because it doesn’t always show up in standard blood or hair tests. One of its lesser-known but critical mechanisms is its strong binding to thiol groups  (–SH). Thiols, found in cysteine, glutathione, and many detoxification enzymes, are essential for maintaining proper metabolic and antioxidant function. Even tiny amounts of mercury can create a biochemical bottleneck by binding to these thiols. 🔬 1.