The toxicology of the newer metals.

In the following discussion of the toxicology of the ' newer' metals, it is perhaps more accurate to refer to them as metals which have only recently become of industrial importance. Most of the metals mentioned have long been known, and in some instances have actually been used in quantity. However, many new types of use have developed, or unusual compounds have become important industrially and have aroused the interest of the industrial hygiehist. It should be realized that the metals and their compounds in general have distinctive characteristics, and that it is somewhat difficult to group their physiological action in the same way as is possible with great groups of organic compounds. For instance, the nitro or amino compounds, or the halogenated hydrocarbons, have many characteristics which permit some evaluation of the toxic qualities of the individual members of the group from what we know of the group in general. The behaviour of the metals and their compounds is far less predictable from this point of view. Characteristics which belong to the group as a whole may vanish with one particular compound, or vice versa. Thus, tin salts are quite harmless. Individuals daily consume quantities of tin that would be a matter of concern if tin were as toxic as many other metals generally regarded as harmless. Yet tin tetrahydride is stated to be one of the most toxic substances, being more poisonous than arsine. The following discussion, therefore, tries to evaluate the known facts about the physiological action of the metals and their compounds as separate entities. Very little is known of some of these substances, either because they have been of no great commercial importance, or because heretofore they have not displayed properties which are distinctive in a physiological sense.