Harmful Effects of the Agent
Human consumption of low concentrations of chlorite or chlorine dioxide and water disinfected with chlorine has been studied and, in general, no adverse effects have been found. One study with many limitations reported an increase in many developmental defects in a community with chlorine dioxide-disinfected drinking waters, but these findings are considered of limited value due to the lack of exposure data and lack of control for many other critical factors.
Animal data suggests neurodevelopmental delay and harm to fetal brain development, with NOAEL at 3 mg/kg-day chlorine dioxide and LOAEL at 14 mg/kg-day and neurobehavioral effects with NOAEL at 3 mg/kg-day and LOAEL at 6 mg/kg-day chlorite. 13
The RfD for chlorine dioxide and chlorite established by the EPA used the NOEL of mg/kg-day and an uncertainty factor of 100 to incorporate interspecies extrapolation and individual variability.
An inhalation RfC has not been established for chlorite due to lack of data. While animal studies of chlorine dioxide are used as proxies for chlorite for many purposes, they are not applicable to inhalation because at ambient temperature, chlorine dioxide is a gas, whereas airborne chlorite would be a particulate. Thus the modes and hazards of exposure of these two chemicals in the air are not relevant to each other.
Cancer risk assessment cannot be done with data available and therefore risk levels are not established.
Absorption, Distribution, Metabolism and Excretion
Little is known from testing in animals and no human studies have been reported to evaluate absorption of chlorite.
Chlorite is rapidly absorbed from the gastrointestinal tract. In single gavage tests in rats, peak plasma levels of chlorine were reached within 2 hours after injection with radiolabeled chlorine. By applying urine excretion data, it has been determined that 35% of the initial dose is absorbed and has a half life of 3.5 hours. However, this testing tracked radioactivity, rather than chemical entitities of the parent compound and the degradation process, and so it is not known in what form the radioactive ion was absorbed.13
Respiratory Tract Absorption
Data is not yet available on chlorite absorption through the respiratory tract.
Chlorite absorption has been tested on the shaved backs of rats, showing maximum absorption after 72 hours with an absorption half-life of 22.1 hours. 13
Chlorite remains in the blood for a long time, with a relatively slow removal process, and thus is distributed extensively throughout the body organs and tissues. Tests in rats showed a 35.2 hour half life in the blood after a single gavage dose. These tests reported highest concentrations in the blood, stomach, testes, skin, lung, kidneys, small intestine, spleen, brain, bone marrow, and liver. 13
Chlorite is expected to be metabolized in a process similar to chlorine dioxide, on which more information is known. It is believed that chlorine dioxide is rapidly reduced in the stomach to nonoxidizing species, such as chloride. In tests in monkeys, the total oxidizing capacity equivalents of chlorine was reduced to 8% within 5 minutes. This rapid reduction has also been reported from in vitro studies.13 Tests using chlorite gavage found the Cl recovered in the urine to be 85% in the form of chloride, and only 15% as chlorite.13
Chlorite is primarily excreted in the urine over the feces by a ratio of 16:1 in the first 24 hours and a ratio of 7:1 in the first 72 hours after a single dose administered by gavage in rats.13