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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

1.   Persistence Assessment

Ammonium is readily converted by bacterial species to nitrate, via the process of nitrification. The primary stage of nitrification, the oxidation of ammonium to nitrite (NO2-) is performed byNitrosomonas(among other) species. Other bacterial species (includingNitrobacter) are responsible for the subsequent oxidation of nitrite to nitrate (NO3-). Nitrification is important in preventing the persistence or accumulation of high ammonia levels in waters receiving sewage effluent or agricultural runoff. Other mechanisms may also act to limit the concentration of ammonia in natural waters: ammonia is readily assimilated by aquatic algae and macrophytes for use as a nitrogen source. Ammonia in the aqueous environment may also be transferred to sediments by adsorption on particulates, or to the atmosphere by volatilisation at the air-water interface. Both processes have been described as having measurable effects on ammonia levels in water; however, the relative significance of each will vary according to specific environmental conditions.

2. Bioaccumulation Assessment

Ammonia is ubiquitous in the aquatic environment as a consequence of the breakdown of plant and animal material and due to animal excretory processes. The generation of ammonia by normal metabolism (protein catabolism) occurs in all animal species, and therefore all animal species have developed effective physiological mechanisms of detoxification (metabolism to other nitrogenous compounds) or excretion. In fresh water fish, ammonia is excreted across the branchial epithelium via passive diffusion.

The following information is taken into account for any hazard / risk / bioaccumulation assessment:

Ammonia does not bioaccumulate and is a product of normal metabolism.

3. Toxicity Assessment

The substance is classified as very toxic to the environment due to the effects on fish. 

4. Summary and overall Conclusions on PBT or vPvB Properties

 The substance is neither a PBT- or a vPvB substance.