An astute observation by the WSJ Health Blog that there's much ado about toxic substances these days prompted an informative Q/A with George Corcoran, president of the Society of Toxicology. He makes an interesting point - one reason we're seeing reports of toxic substances, such as pharmaceuticals in drinking water, is simply that we're now able to *measure* such things at such a small level. Which raises the question: Are we measuring something that is now there that wasn't before, or have there long been such background levels of toxic substances, but now we're simply seeing them?