Is Cesium Formate Toxic?

As this compound’s popularity increases, it is vital that its toxicity is assessed, to ensure workers dealing with this chemical regularly are appropriately trained and protected.

However, as this chemical is relatively new for industrial uses, studies in this area are still limited to animal-based research, from which its harmful behaviour must be inferred. Nonetheless, important information can be obtained from various laboratory tests that have been carried out to assess caesium formate’s toxicity, using several test animals, including rodents and rabbits.

Oral, Skin And Eye Toxicity

It is currently assumed caesium formate does not represent a serious threat, in the case of accidental ingestion or contact with skin and eyes. At least in rats, this compound presents low levels of oral toxicity, with reported LD50 values ranging from 1700 to 2000 mg/kg. Extrapolating from rodent studies, exposure to high dosages may cause gross signs of stress, including convulsions, respiratory and digestive problems and excessive salivation; but it’s not expected workers would be exposed to these levels.

A similar result was demonstrated in case of direct contact with skin and eyes. Some evidence of mild skin irritation was visible, but partial or complete recovery was observed in all animals. With regards to application directly to the eyes, animals experienced some redness and inflammation of the iris, but all affected rabbits had recovered fully within 24 hours. Despite rare, some animals exhibited extreme symptoms including oedema and blistering of the conjunctiva, but this had also cleared after 14 days. Despite the lack of research in humans, results obtained from these animal studies are strong enough to classify caesium formate as slight to moderately irritant.

Prolonged Exposure

The number of tests assessing the impact of prolonged exposure to caesium formate is extremely limited, but a study conducted over 27 weeks detected no significant outcome in rats drinking water containing low levels of caesium formate (0.5% and 1%). In theory, it’s assumed that any effects will be due to formate anion and caesium cation after dissolution, which are converted to formic acid and caesium chloride in the stomach. As it’s been demonstrated that Cs+ is more toxic than Na+, but less than K+, Li+or Rb+, any toxicity caused by caesium-containing compounds is more likely due to the anion present, such as formate.


Despite limited research in this area, there is no indication that caesium formate may potentially be carcinogenic or mutagenic. Preliminary studies with human lymphocytes observed no chromosomal aberrations even at high exposure levels.

In conclusion, studies looking at acute or prolonged toxicity have clearly demonstrated the harmless nature of this compound, when used under normal circumstances, which make this a particularly attractive product to use in large-scale industrial applications.

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