Urea

Short-term toxicity to fish

Description of key information

Urea is of very low acute toxicity to fish: reported LC50 values range from >6810 to 28000 mg/L

Key value for chemical safety assessment

LC50 for freshwater fish:

6 810 mg/L

Additional information

Urea is of very low acute toxicity to fish. The 48 hour LC₅₀of urea in golden orfe is reported to be >10000 mg/l. This can also be considered as the NOEC. The results reported by the two laboratories were identical. The effects of urea on survival, food utilization and oxygen consumption of the fresh water fish Oreochromis mossambicus were studied. The percentage survival of O. mossambicus when exposed to different concentrations of urea at 24, 48, 72 and 96 h exposures was noted and it was found that 22000 and 38000 mg L−1 urea concentration were sublethal and lethal, respectively. The median lethal concentration, which killed 50% of the fish during 96 h exposure, was 28000 mg L−1. Rearing the fish in increasing sublethal concentrations of urea, it was found that the feeding rate decreased from 34.341 ± 7.067 mg g live fish−1 d−1(control) to 13.921 ± 2.315 mg g live fish−1 d−1at the highest concentration of urea (22,000 mg L−1). Growth rate was drastically reduced. The consumption of oxygen in O. mossambicus diminished from 0.962 ± 0.208 to 0.645 ± 0.118 mg g live fish−1 h−1 when reared in the highest sublethal concentration of urea. The 96 hour LC₅₀of urea to B. barna was > 9100 mg/l. The NOEL was 4961 ppm. The 96 hour acute LC₅₀of urea to golden orfe fish is reported in a further study to be >6810 mg/l.