The "hoopla" about Thimerosal: Thimerosal contains ethyl mercury, at levels which the CDC claims are safe. Shark, Tilefish, and other fish contain methyl mercury, at levels which the EPA considers safe once a month. Both of these institutions have the burden of protecting many, sometimes at the expense of the few, so these levels may not be safe for small infants, pregnant women, anyone with mitochondrial disorders. My education thus far has lead me to understand over and over that heavy metals are neurotoxic: lead, mercury, orificenic. you must decide what level of poison is right for you, as for me: I know why the mad hatter is mad.