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Are sweat & grime contaminants?

While wikipedia is a mediocore source of info, it states sweat contains the following.

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It also contains minerals, as well as lactate and urea. Mineral composition will vary with the individual, the acclimatisation to heat, exercise and sweating, the particular stress source (exercise, sauna, etc.), the duration of sweating, and the composition of minerals in the body. An indication of the minerals content is: sodium 0.9 gram/liter, potassium 0.2 gram/liter, calcium 0.015 gram/liter, magnesium 0.0013 gram/liter[10]. Also many other trace elements are excreted in sweat, again an indication of their concentration is (although measurements can vary fifteenfold): zinc (0.4 mg/l), copper  (0.3 - 0.8 mg/l), iron (1 mg/l), chromium  (0.1 mg/l), nickel (0.05 mg/l), lead (0.05 mg/l).

But we are not just talking sweat.  Depending on the person, there may also be things like sun-screen and bug repellent.  There may be chemicals transfered to the skin from clothing, packs, fuel canisters, paddles, etc. Not to mention, the residue left over in the bodily function areas (yuck).

Again I am not saying this is a problem, because we are talking such small quantitites in a big watershed.  But the same applies to the impact of soap, which although maybe amounts to higher mass than those things washed off our bodies, may only contain "natural vegetable-derived ingredients" (camp soap). Even something like ivory soap has pretty benign ingredients.