Aluminum

Abstract

Because of this element's electrochemical properties, its positvely charged ions form very tight chemical bonds with other anions such that dissociation is minimal in neutral or near‐neutral‐pH environments. Since most living organizations operate at or about such pH levels, by implication most naturally occurring aluminum compounds would display minimal potentials for cellular or subcellular interactions. Its binding forces, in addition to making this element available only recently (at the time of writing), has also meant that aluminum was relatively unavailable to the milieu intériur. However, since progressively more of the metal and its compounds came into common human use and commerce, ultimately its wide usage could be expected to eventually result in the possibility intimate human contact and finally, human health and hazard concerns. These events have indeed occurred so that aluminum and its possible association with neurological disorders became a prominent health issue of the late twentieth century. Because of the foregoing electrochemical physical realities, concerns have focused on the element's health effects per se, with little or attention directed at effects of aluminum compounds, such as chloride, phosphate, and sulfates. This should also not be unexpected, given their relative biological inavailability. Obviously, some aluminum compounds do ionize sufficient to lower pH in aqueous environments (e.g., aluminum chloride or phosphate) and act as simple irritants. However, most other aluminum compounds, as expected have had very little apparent biologic availability or effects, and thus are accorded little scientific attention as compounds per se. These facts are reflected in the content of contemporary biomedical literature. Although multiple aluminum compounds have been studied, few, if any, are studied except as they serve to “transport” aluminum into the body. The overwhelming majority represent interest in aluminum's effects alone rather than an individual compound's possible bioimpact. For these reasons, this chapter deals mainly with aluminum as an element and the most common prevalent form: the oxides. Since its other compounds as such are the subject of so little current investigation, these other compounds are considered separately later in this chapter.