Iron trinitrate

Endpoint summary

Additional information

Based on the available data it is evident that the Fe cation is considered the most toxic component following exposure to Iron trinitrate. For the purposes of risk assessment the following aquatic endpoints for iron are considered to provide a risk envelope approach for nitrate toxicity and therefore further consideration of nitrate is not required. The Fe toxicity endpoints are summarised below:

Acute toxicity to fish: LC50s= 0.41, 0.48 and 1.75 mg total Fe/L at pHs of 5.5, 6.0 and 7.0 (mean 0.88 mg/L)

Long term toxicity to fish: NOEC lies between 0.24 (control) and 1.5 mg Fe/L based on survival growth and hatchability (NOTE: concentrations thought to exceed the solubility of Iron under environmental conditions. Quoting a NOEC as the control/background Fe concentration as the NOEC is potentially misleading and this value should be treated as a conservative estimate.

Short term toxicity to invertebrates: based on the results of a 21 -day Daphnia reproduction test a conservative estimate of the 48 hour EC50 can be concluded. The 48 -h EC50 was considered to be >18 mg/L based on nominal concentrations and >12.8 based on twa measured concentrations. The results of an acute prelimimary test also identified a NOEC of 10 mg/L.

Long term toxicity to invertebrates: reliable results were obtained from a 21-day Daphnia reproduction test that demonstrated a NOEC of 8.1 mg total FE/L based on measured TWA concentrations.

Toxicity to aquatic algae and cyanobacteria: 72 -h EbC50 11 mg Fe/L and NOEC 3.2 mg Fe/L.

Toxicity to microorganisms: there is substantial evidence to assume a NOEC of 500 mg Fe/L.

 

Conclusion

Iron is an essential trace element for fish, aquatic invertebrates and plants. The effects of iron sulphate on aquatic organisms in short term tests are observed at nominal exposure concentrations in the range 1 - 1 000 mg/L salt with the majority being in the range 10 - 100 mg/L. Effects arising from long-term exposures are observed at nominal concentrations in the order of 1 mg/L. At all of these concentrations it can be expected that, under the test conditions, most of the iron will be present as undissolved and precipitated ferric hydroxxide. It is therefore highly likely that observed effects on fish and invertebrates will be due to smothering or clogging of the gills or respiratory membranes and effects on aquatic plants and algae will be due to impairment of photosynthesis by light interception. Growth of aquatic plants and algae can also be inhibited as a consequence of nutrient (phosphate chelation).