The chemistry underlying chromate toxicity

Abstract

The fundamental processes involved in the expression of the toxicity of chromate have been particularly well studied in recent years and have attracted a remarkably interdisciplinary group of researchers ranging from traditional toxicologists through molecular biologists to inorganic chemists. There is a clear chemical interest in the problem because chromium in oxidation state six is an established human carcinogen (a) associated with lung cancers. Major reviews of this area have appeared emphasizing its general importance r or specific areas such as studies involving cell or tissue culture r The aim of this short article is not to attempt any comprehensive review but to provide a basically inorganic audience an insight into the problem and an understanding of how inorganic chemistry is important in understanding the expression of the toxicity of chromate. In part the interest in chromate toxicity can be traced to the fact that chromate is an established human carcinogen which is, because of its reactivity, particularly amenable to mechanistic studies (4-7). However, the complicated redox chemistry of chromium in aqueous solution has so far prevented a clear picture as to which mechanism(s) are important in the formation of DNA lesions both in vitro and in vivo. In terms of understanding the in vivo effects one particularly important study has shown that chromate is carcinogenic in rats by inhalation, for some reason this important Study, in which chromate was administered by the route most appropriate to model the suggested effects in humans is frequently overlooked r We shall endeavour to explain why the physiological response of chromate may be very sensitive to the mode of administration as we proceed.