Tissue distribution of absorbed humic acids.

Distribution of humic acids (HA) in rats was studied using radioiodinated HA injected intraperitoneally. Distribution of (125)I was also studied for comparison. The distribution pattern of HA differed greatly from that of (125)I. Except in the thyroid and skin, (125)I was excreted from the body within 24 hours, whereas a large proportion of HA remained in the liver, kidney, skin, thyroid, bone and muscle. The difference in the distribution pattern and organ/serum radioactivity ratio suggests different kinetics for (125)I and (125)I-HA. The distribution pattern of HA correlated very well with the increased prevalences of organ diseases in the blackfoot disease endemic area, as reflected in epidemiologic studies. It is hypothesised that HA-metal complexes are possible etiological factors of diseases such as goitre, hepatoma, bladder cancer, vascular disease and diabetes mellitus, and that free radicals are the common causative factor.