Tolerância
Tolerância
Tolerância
SODIUM CHLORITE
SUMMARY REPORT
1. Sodium chlorite is used in veterinary medicine as a medical disinfectant in post-milking teat dip
products used topically for the control of mastitis in dairy cattle.
2. When sodium chlorite (Na ClO2 ) is mixed prior to use (in the formulated product) a chemical
equilibrium is established containing
chlorous acid (HClO2 ) which degrades to chlorine dioxide (ClO 2 a gas), and to a lesser extent
sodium chlorate (NaClO3 ). The chlorate (ClO 3 ) eventually degrades to ClO2 and NaCl as major
products. The chlorous acid and chlorine dioxide are responsible for the microbicidal action of
the product, via non-specific oxidative damage to bacterial membranes.
3. In general, the toxicity studies presented were not conducted to current scientific protocols, and
clear NOEL's were generally not established for each compound, however all three compounds
(chlorine dioxide, sodium chlorite and sodium chlorate) tended to produce the same pattern of
toxicity.
4. Chlorine dioxide, sodium chlorite and sodium chlorate were all shown to be well absorbed by the
oral route in rats, by using radiolabelled compounds (Cmax around 1-2 hours). The plasma
elimination half lives ranged from 35 to 44 hours. The main route of excretion for sodium
chlorite and chlorine dioxide appeared to be via the kidneys, predominantly as chloride (32 %
and 27 % of the dose respectively at 72 hours), with some chlorite (6 % and 3.5 % of the dose
respectively at 72 hours), and a little chlorate (0.73 % of the dose at 72 hours). For sodium
chlorite, 83 % of the recovered dose was found in urine, and 13 % in faeces. For chorine dioxide
and sodium chlorate no radioactivity was detected in expired air.
5. Repeat-dose toxicity tests with chlorine dioxide, sodium chlorite and sodium chlorate all
produced a similar spectrum of dose-related toxic effects in various animals species (rat, mouse,
rabbit, African green monkey). The main effect was on haematological parameters (reduced
glutathione concentration, reduced erythrocyte counts, reduced PCV, reduced haemoglobin
concentration, reduced osmotic fragility of erythrocytes, haemolysis, methaemoglobin
formation) which was observed in rats and mice. Inhibition of thyroid hormone synthesis was
observed in rats and African green monkeys with chlorine dioxide (9 mg/kg bwt/day in drinking
water), which was dose-related and reversible on cessation of treatment. A NOEL of 3 mg/kg/day
was established for chlorine dioxide which did not affect serum thyroxine levels, whereas both
sodium chlorite and sodium chlorate had no effect on thyroid function in monkeys at doses of
60 mg/kg bw/day for 30-60 days.
6. Overall, studies with chlorine dioxide, sodium chlorite and sodium chlorate suggest that they are
not teratogenic in mice, rats or rabbits. At high doses of chlorine dioxide and sodium chlorite
(100 mg/l of drinking water) the number of implants and live foetesus per dam tended to be
reduced, and foetal weight and length and pup weight were decreased. At lower doses (10 mg/l of
drinking water) there were no effects on female fertility, gestation length, litter size and weight.
Male fertility was unaffected by chlorine dioxide, but sperm development was affected after
treatment with 100 mg/l of sodium chlorite. Exposure of the pups to both chlorine dioxide and
sodium chlorite resulted in reduced thyroid hormone levels (T 3 and T 4 ) and inhibition of
locomotor activity, suggesting delayed neuro-behavioural development in young animals.