Pharmacodynamics and toxicity of chlorine in drinking water in the rat.

Chlorine interacts with organic materials in surface water, leading to the formation of trihalomethanes, that may be carcinogenic. Studies were conducted to investigate the pharmacodynamics and toxicity of chlorine (0, 1, 10, 100 mg 1(-1] in drinking water in rats. Blood glutathione (GSH) was significantly decreased after 6 months of treatment and this effect persisted after 1 year treatment in the 10 and 100 mg 1(-1) groups. Treatment groups showed an increase in blood osmotic fragility. The acute study revealed that GSH was significantly decreased as early as 30 min after the administration of 30 and 120 micrograms chlorine. The effect was maintained up to 1 h. However, the GSH level returned to control value by 2 h. Blood osmotic fragility of the acute exposure was incresed after 15 min and was without change after 30 min. Of the hematological parameters only the red blood cell count and hematocrit were significantly decreased in the 100 mg 1(-1) group after 3 months of treatment. An examination of blood chloroform content in all the groups after 4, 6, 9 and 12 months showed no significant difference compared with the control. Chlorine administered chronically in drinking water for 3 months increased the incorporation of 3H-thymidine into nuclei of rat kidney and testes in the 100 mg 1(-1) group.