The toxicity of any substance is a matter of degree, not just what it is. Without sodium, you would die. Too much sodium, and you will die. Even water can be poisonous, in sufficiently large amounts - you may recall a year or so ago, when a radio station was holding a contest ("Hold Your Wii!"), in which the person who could go the longest without urinating after drinking several gallons of water would win a Nintendo Wii. The lady who won collapsed shortly thereafter and died, killed by the toxic levels of water in her stomach.
The danger level for formaldehyde exposure would appear, from a cursory scan of the available data, to be on the order of 0.1 ppm. Would you happen to have a figure on the formaldehyde levels of various vaccines? (I presume the level would vary from formulation to formulation.)
(Added later)
Ah, I found a source for information on the question of formaldehyde and vaccines:
Quote:
The average quantity of formaldehyde to which a young infant could be exposed at one time may be as high as 0.2 mg (see table below). This quantity of formaldehyde is considered to be safe for two reasons. First, formaldehyde is essential in human metabolism and is required for the synthesis of DNA and amino acids (the building blocks of protein). Therefore, all humans have detectable quantities of natural formaldehyde in their circulation (about 2.5 ug of formaldehyde per ml of blood). Assuming an average weight of a 2-month-old of 5 kg and an average blood volume of 85 ml per kg, the total quantity of formaldehyde found in an infant’s circulation would be about 1.1 mg — a value at least five-fold greater than that to which an infant would be exposed in vaccines. Second, quantities of formaldehyde at least 600–fold greater than that contained in vaccines have been given safely to animals.
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Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.