Fulvic Acid as additive 

Fulvic acid is a water-soluble, natural organic substance of low molecular weight which is derived from humus, often found in surface water. Fulvic acid contributes to the formation of trihalomethanes in chlorinated water supplies, and can contribute to organic fouling of ion exchange resin beds.   http://www.wqa.org/WQIS/Glossary/Fulvic-acid.html ,  http://www.ida.net/users/srdist/fulvic.htm

Kashin-Beck disease is an endemic arthritis seen in Siberia, Mongolia, Tibet, and the remote areas of Red China ("the people's paradise"). The cause is almost certainly selenium deficiency coupled with fulvic acid (from rotting organic material;  it poisons procollagen type II processing (see Copper and Collagen), Eur. J. Biochem. 202: 1141, 1991) in the drinking water (J. Tox. 35: 79, 1992; Am. J. Clin. Nut. 57(S2): 259S, 1993; Bio. Trace El. Res. 31: 1, 1991).  Animal model: Biochem. J. 289: 829, 1993.  Histopathology Virch. Arch. A. 423: 483, 1993.