Effect of photocorrosion on cadmium sulfide suspensions applied in animal inhalation studies with CdS particles

Cadmium sulfide aerosol (90 g Cd/m³) was generated from an aqueous suspension for 12 weeks and the ratio of Cd⁺⁺/Cd_total in the suspension and the resulting aerosol was determined. After 4 weeks the concentration of Cd⁺⁺ in the suspension and the aerosol leveled off at 43.5±11.4% and 35.8±6.8%, respectively. Therefore, lung tumors in rats observed after inhalation exposure to such CdS aerosols (Glaser et al. 1990) may have been caused not only by the effect of CdS but also by the influence of inhaled Cd⁺⁺ or CdSO₄. The contribution of CdS particles to the observed lung tumor rate depends on the bioavailability of CdS retained in the lungs. The photochemical decay of CdS in aqueous suspensions only occurred when exposed to light and adjusting the suspension up to pH 3 did not increase the decomposition rate of CdS. Ethanolic suspensions of CdS are much more stable than aqueous ones and experiments with suspensions kept under shield gases showed that the decay of CdS is not dependent on oxygen.