Potassium hydrogencarbonate

Endpoint summary

Additional information

There are some reliable data available for acute toxicity on fish (Oncorhynchus mykiss) and Daphnia (Ceriodaphnia dubia and Daphnia magna).

In a 96-h acute toxicity study according to national guideline FIFRA Guideline 72-1 the 96-h LC50 for Rainbow trouts (Oncorhynchus mykiss) was 1300 mg a. i. /L (95% CL: 1200 - 1900 mg a. i. /L). The NOEC, based on mortality, was 430 mg a. i. /L.

In a 48-h acute toxicity study, water fleas (Daphnia magna) and Ceriodaphnia dubia were exposed to KHCO3. The 48-h EC50 were 650 mg a. i. /L. and 630 mg a. i. /L, respectively. Ceriodaphnia dubia is somewhat more sensitive than Daphnia magna.

Toxicity tests on aquatic plants and sediment organisms as well as long-term toxicity tests are not available.

The abiotic dissociation of potassium carbonate and potassium hydrogencarbonate in water results in the formation of potassium and carbonate ions. Potassium and carbonate are essential for almost all living organisms including aquatic plants and algae and natural components in their habitats. Furthermore potassium as well as carbonate is ubiquitously present in the environment, occurring naturally in minerals, soils and sediments, natural waters (oceans, lakes, rivers), biota and human beings. This is in line with the fact that standard guidelines, e.g. OECD 201, aquatic test media should be enriched with potassium (e.g. as KH₂PO₄) and carbonate (e.g. as NaHCO₃) to ensure appropriate living conditions. Therefore, potassium hydrogencarbonate is not expected to have an intrinsic toxic activity to aquatic organisms and sediment organisms.

However, the only possible effect of potassium hydrogencarbonate would result from the pH effect. The pH is expected to remain between environmentally acceptable ranges. A significant increase of the pH of the receiving water is not expected. Generally, the change in pH of the receiving water should stay within a tolerated range of the pH at the effluent side and for this reason no adverse effects on the aquatic environment are expected due to the production or use of potassium hydrogencarbonate, if emissions of waste water are controlled by appropriate pH limits and/or dilutions in relation to the natural pH and buffering capacity of the receiving water.

A generic PNEC cannot be derived from single-species toxicity data for potassium hydrogencarbonate, as the pH of natural waters as well as the buffer capacity of natural waters show considerable differences and aquatic organisms/ecosystems are adapted to these specific natural conditions, resulting in different pH optima and pH ranges that are tolerated (EU RAR NaOH (2007) and HERA (2005)). According to the OECD (2002a) and OECD (2002b), a lot of information is available about the relationship between pH and ecosystem structure and also natural variations in pH of aquatic ecosystems have been quantified and reported extensively in ecological publications and handbooks.