Skin Permeation and Cutaneous Hypersensitivity As a Basis for Making Risk Assessments of Chromium As a Soil Contaminant

A literature review of experimental and human exposure studies of skin permeation and cutaneous hypersensitivity reactions evoked by chromium was carried out to provide a basis for making a risk assessment of chromium as a soil contaminant. In vitro and in vivo studies demonstrated that 1 to 4% of the applied dose of hexavalent and trivalent chromium to guinea pig skin penetrated skin within 5 to 24 hr after application. Ultrastructural investigations showed that hexavalent chromium localized intracellularly and extracellularly in the upper layers of guinea pig epidermis. Only minute quantities of hexavalent chromium are required to elicit a positive hypersensitivity reaction in susceptible individuals; using a patch dose of 20 micrograms, only 2 micrograms were required to evoke a positive skin reaction in hypersensitive subjects. The potential of hexavalent chromium to produce a skin sensitization reaction is readily demonstrated using animal models. The incidence and characteristics of chromium-induced skin hypersensitivity as a clinical entity are described. A health effects survey of populations exposed to chromium slag in soil in Tokyo, Japan extending over 8 years indicated a tendency toward symptoms characterized as headache, chronic fatigue, and gastrointestinal complaints, positive occult blood tests, minute hematuria and albuminuria suggestive of incipient renal disease, and a tendency toward an increase in contact dermatitis that was seasonally related. Multicenter patch test titration studies in human subjects using an incidence of positive patch tests of 10% or less showed that the threshold for skin hypersensitivity reactions to hexavalent chromium was determined to be of the order 0.001%, equivalent to 10 ppm or 10 mg/kg or 10 mg/L.(ABSTRACT TRUNCATED AT 250 WORDS)