One more defense,
In a book by Michael McCann Ph.d, "Artist Beware," Cobalt Carbonate (who can afford Cobalt Oxide even though it is less toxic) has the folowing toxicity ratings: (pg 125)
Skin Contact: Slight
-These ratings are higher than Manganese Dioxide and equal to Lead in inhalation and ingestion. (which manifest themselves differently of course).
In his explanation of toxicity ratings of "high" he advises(pg 62); "Avoid highly toxic chemicals, if possible. If they must be used, use very careful precautions such as local exhaust ventilation and other precautions."
"General Hazards"(pg 125)
" Probable human carcinogen from animal studies. Repeated skin contact may cause allergies, especially at elbows, neck, and ankles. Chronic inhalation may cause asthma, heart problems, and pulmonary fibrosis. ingestion may cause acute illness with vomiting, diarrhea, and sensation of hotness."
Let's do some math, I will use the example of 1/4 tsp per 500 pounds. Without weighing it out I would bet that would weigh about 1-1.5 grams or 1000-1500 milligrams. Divide that into the 500 lbs of clay that comes to 2-3 milligrams per pound of clay. If used as a body colorant this ratio woud be much higher. If you take the toxicity dose of my previous source of "greater than 5 milligrams per day" the above numbers and chronic effects above become much more plausible. Of course one is not eating the clay ( although I do know several who lick it a lot) or snorting lines of it. But this, for me at least, would convince me not to come into contact with it on a regular basis.
I hope this illuminates where I was coming from.
Sorry for the initial vagueness. Kendall