Registration Dossier

Administrative data

Link to relevant study record(s)

Description of key information

NaDCC is unstable in the body, particularly the stomach because the free available chlorine is rapidly reduced. CYA, or its salt is the stable degradation product. Therefore CYA or its sodium salt is the substance of interest for the toxicokinetic studies. 

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

Studies have been conducted on the absorption, distribution, metabolism and excretion of radiolabelled sodium cyanurate (equivalent to 77.5% CYA) after single i.v. and repeated oral administration. No metabolism or accumulation was demonstrated in either of the two animal studies in dogs and rats with 100% of the radioactive label recovered in urine and faeces. Over 98% of the cyanuric acid was absorbed from the GI tract. The findings of the animal studies are upheld in a pilot study in humans ingesting swimming pool water where > 98% of a measured dose of CYA was recovered in urine within 24 hours of dosing (Dufour et al (2006). In oral ingestion studies in 2 volunteers, total recovery of cyanuric acid was 21 and 21.2 mg and interpolated 90% excretion was at 3.1 or 3.5 h (t1/2~ 1 h). The volunteers ingested 100 ml of water containing 214 ppm cyanurate (or 21.4 mg cyanurate) thus essentially 100% was recovered in the urine. 

In dermal absorption studies where human skin was tested with a pool concentration of unlabelled cyanuric acid and chlorine, only 0.06 μg/cm2total cumulative absorption was detected over the 24 h exposure period (Moody 1993). Employing a value of 1.83 m2for the total body surface area of a 70 kg human, would imply an exposure of 1.1 mg for a 24 h exposure period. Assuming a worse case maximum exposure time of 5 h daily the data suggests that 0.2 mg/day would be absorbed through a swimmers skin. For a standard water cyanuric acid concentration of 55 ppm, 0.2 g of cyanuric acid would be contained in 3.6 mL pool water. Therefore exposure by the oral route could easily supersede that of dermal.