JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) and Brogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives. Subchronic toxicities of C102, NaCIO2, NaCIO3 and NH2C1 were studied in the African Green monkeys (Cercopithecus aethiops). The chemicals were administered in drinking water during 30-60 days subchronic rising dose protocols. The only unexpected and significant toxic effect was elicited by C102; this chemical inhibited thyroid metabolism in the animals at a dose of ca. 9.0 mg/kg/day. A statistically significant decrease of serum thyroxine occurred after the fourth week of exposure to 100 mg/l.concentration. The extent of thyroid suppression was dose dependent in each individual monkey, and was reversible after cessation of exposure. NaCIO2 and NaCIO3 failed to elicit similar effects in doses up to ca. 60 mg/kg/day. Also, NaCIO4 or NH2Cl did not cause T-4 suppression in doses of 10 mg/kg/day. The selective thyroid effect of C102 was unexplained and it appeared to be paradoxical since C1O2 was rapidly reduced by the oral and gastric secretions to nonoxidizing species (presumably Cl-). No evidence of thyroid effects were detected in the serum of human volunteers who ingested -1 mg/I. of C102 in drinking water as a result of routine use in the community water treatment process.Sodium chlorite induced dose-dependent oxidative stress on hematopoesis, causing decreased hemoglobin and red cell count and increased methemoglobin content. At the same time, serum transaminase (SGPT) levels showed significant subclinical elevation. The hematologic effects of NaClO2 rebounded during exposure indicating compensatory hemopoietic activity taking effect during oxidative stress. Sodium chlorate and chloramine did not induce detectable hematologic changes in the animals.