Potassium hydroxyoctaoxodizincatedichromate(1-)

Endpoint summary

Additional information

There is no information on the toxicokinetics of zinc potassium chromate by any route of exposure. Some data are available on the toxicokinetics of other sparingly soluble chromates but most of the available information on the toxicokinetics of chromates comes from water soluble chromates. In one study, workers in strontium chromate plants showed significantly elevated urine chromium levels suggesting bioavailability of inhaled strontium chromate. After inhalation of highly water soluble chromates, considerable amount of chromium deposited in the lung is rapidly transferred into the blood and taken up by erythrocytes or visceral organs. According to some studies, the uptake of chromium from the lungs may be up to 50%. Inhalation of sparingly soluble zinc chromate has also shown to result in increases in blood and urine chromium levels, and in one study comparing the kinetics of sodium and zinc chromate after intratracheal instillation in rats zinc chromate resulted in higher maximum blood levels than sodium chromate, although the absorption was slower than the absorption of sodium chromate. Absorption of chromium from zinc potassium chromate after inhalation is assumed to resemble that of zinc chromate.

Oral absorption of hexavalent chromium is limited by reducing conditions in stomach resulting in the reduction of the hexavalent chromium to trivalent chromium. Absorption of hexavalent chromium from gastrointestinal tract shows significant variation between individuals. Generally absorption of <10% has been identified in humans after oral administration of highly water soluble chromates. No data is available on the oral absorption of less soluble chromates in humans. Comparative repeated animal experiments using sodium chromate and sparingly soluble calcium chromate suggest that there may be no huge differences in oral bioavailability between these chromates.

Dermal absorption of <1% for water soluble sodium chromate has been identified in animals. No data is available on poorly soluble chromates.

Once in the blood, chromium is distributed to various organs in the body. Especially chromium levels in kidneys, liver, spleen and testes have been shown to increase in animals after inhalation or oral exposure to water soluble chromates. In blood, hexavalent chromium is rapidly taken up by the erythrocytes by specific transport mechanisms, reduced to trivalent chromium mainly by intracellular glutathione and bound irreversibly in hemoglobin. Also plasma can reduce hexavalent chromium to trivalent chromium and reduction has been shown to occur also in lungs. Chromium intake into cells is much greater when in the hexavalent oxidation state and extracellular reduction to trivalent chromium serves to prevent its uptake. In addition to glutathione, ascorbic acid is another important reducer of hexavalent chromium.

Transplacental transfer has been shown to occur after intravenous administration of soluble hexavalent chromium (sodium chromate). No data on the transplacental transfer of strontium chromate is available.

Excretion of chromium occurs in the urine and faeces. In urine no hexavalent chromium has been detected because of the reduction of hexavalent chromium to trivalent form in the body. After oral administration, most of the chromium is excreted in the faeces with only few percents entering the urine (usually <2%). Inter-individual variation in urinary excretion may be high. Inhaled chromium absorbed into the body is excreted mainly into the urine. Urine as the main route of excretion of absorbed chromium is supported also by intravenous studies showing that 60% of the administered dose of sodium chromate is excreted into the urine within 25 days.

No additional studies on the toxicokinetics of zinc potassium chromate are suggested.