Ammonium hydrogendifluoride

Endpoint summary

Additional information

A correlation between fluoride levels in earthworms and elevated soil fluoride levels from polluted sites has been demonstrated, however levels were due to the soil content of the worm gut. Elevated fluoride content in woodlice collected from the vicinity of an Al-reduction plant has been demonstrated (Janssenet al, 1989). Sloofet al(1989) note that uptake of fluoride into plants from soil is low as a consequence of the low bioavailability of fluoride in the soil and that atmospheric uptake is generally the most important route of exposure. A relatively high rate of fluoride uptake is noted for grass species, and the consumption of fluoride containing plants may lead to elevated fluoride levels in animals and humans. Sloofet al(1989) conclude that the limited data indicate that fluoride biomagnification in the aquatic environment is of little significance. Fluoride accumulates in aquatic organisms predominantly in the exoskeleton of crustacea and in the skeleton of fish; no accumulation was reported for edible tissues. In the terrestrial environment, fluoride accumulates in the skeleton of vertebrates and invertebrates. The EU RAR for HF (2001) notes that the lowest fluoride levels are found in herbivores, with higher levels in omnivores and highest levels in predators, scavengers and pollinators; the findings indicate a moderate degree of biomagnification. Vertebrate species store most of the fluoride in the bones and (to a lesser extent) the teeth; elevated levels of fluoride in the bones and teeth have been shown in animals from polluted areas.

Bioaccumulation of ammonia in biota is not considered of importance in the environment as it does not accumulate in lipid-rich tissues in the same manner as organic chemicals, even though levels of ammonia in the blood of exposed animals may increase following exposures.

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.