Registration Dossier

Administrative data

Description of key information

Animal studies with sodium chlorate show a low acute toxicity after inhalation (LC50(4.5h) > 5.59 mg/l), dermal (LD50(24h)  > 2000 mg/kg bw) and oral (LD50 = 4950-6250 mg/kg bw) exposure. Numerous human case studies are reported. Due to vomiting occurring, sometimes rapidly after ingestion, the absorbed quantity is often uncertain. Therefore, variability occurs in the doses causing lethality. Since the 1960s, survival to higher dose levels of chlorate, up to 200 grams (± 3.33 g/kg bw), has increased due to the possibility of dialysis treatment in case of renal failure. 
Acute toxicity of chlorate is mediated by methaemoglobin. There are marked species differences in susceptibility to form methaemoglobin. Humans are more affected than rodent species. Infants, particularly neonates, are more prone to methaemoglobinemia than older children and adults and are consequently likely to be more susceptible to the toxicity of chlorate. Related to the rapid urinary excretion, the highest levels of chlorates are reached in the kidneys. Nephrotoxicity also seems mediated by methaemoglobin catalysis.
An evaluation by the French poison control center of sensitivity of humans to sodium chlorate compared to rats led to the following conclusion: If one considers that 50% methemoglobinemia starts to induce signs that may lead to death in the absence of treatment, the dose would be about 20 g / kg for the whole population and 4.5 g / kg for the most sensitive part is the same range as rats.
Despite the low acute toxicity in animals, sodium chlorate is considered as harmful to humans due to available data on human lethal effects. Sodium chlorate is classified Xn.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
LD50
5 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Dose descriptor:
LC50
5 590 mg/m³

Acute toxicity: via dermal route

Endpoint conclusion
Dose descriptor:
LD50
2 000 mg/kg bw

Additional information

Animal studies show a relatively low acute toxicity with oral LD50 around 5 grams/kg or higher. In humans, doses of 5 to 10 grams (± 83-166 mg/kg bw1) can be fatal in adults, and doses of 2 grams (± 0.2 g/kg bw1) in children. But also multiple cases are described surviving intakes ranging from 40 g (± 666 mg/kg bw[1]) to even 150-200 grams (± 2.50-3.33 g/kg bw1). Which is likely related to the possibility of dialysis treatment in case of renal failure after 1960s. There are no fatalities reported in recent years. The primary concern for acute chlorate exposure is oxidative damage to red blood cells. Despite low acute toxicity in animals, human experience indicates that classification of sodium chlorate as harmful is justified.There are no concerns related to dermal and inhalatory exposures,besides of hazards of ignition of dried sodium chlorate on clothing. This is supported by a report by the French poison control center that concludes: if one considers that 50% methemoglobinemia starts to induce signs that may lead to death in the absence of treatment, the dose would be about 20 g / kg for the whole population and 4.5 g / kg for the most sensitive part is the same range as rats.

[1]Estimated intakes per kg bw were calculated with adefault body weight assumption of 60 kg for adults, 10 kg for children and 5 kg for infants (WHO 2004).

 

Justification for classification or non-classification

Despite the low acute toxicity in animals, sodium chlorate is considered as harmful to humans due to available data on human lethal effects. Sodium chlorate is classified Xn.

Results from acute dermal and inhalation studies show that sodium chlorate does not require classification.