Lets face facts. There are many dangerous chemicals. On a historic basis one of the most deadly is Di-Hydrogen Monoxide. Ever since the chemical companies started mixing Di-Hydrogen Monoxide with pesticides and Atomic energy companies began using it, our Rivers, Lakes, and Streams have be come loaded with this universal solvent. Now it's even showing up in the oceans.
Besides Di-Hydrogen Monoxide the elements Silver, Iron, Iodine, Copper, and others are making it into vitamin and mineral supplements. The toxicity of Copper and Silver have long been understood. That is why you find Copper and Silver plated door knobs and sink faucets in hospitals. The toxicity of any material is dependent on the dosage. Even drinking too much water will kill you as your electrolyte balance will become so low that your electronic brain waves will become unable to keep your heart beating.
http://www.nbcnews.com/id/16614865/ns/us_news-life/t/woman-dies-after-water-drinking-contest/