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Toxicity to terrestrial plants

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Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
other: Information on major hydrolysis product of the registered substance (released rapidly on contact with water/moisture).
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Report of experimental study published in US state agricultural station journal: single test concentration for soil application.
Justification for type of information:
Part of weight-of-evidence approach adapting the information requirements of Annex IX 9.4.3 and Annex X 9.4.6 under REACH in accordance with Annex XI Section 1.2. Lithium hexafluorophosphate is reactive and unstable in water and air. Reaction in contact with water proceeds rapidly, with release of hydrogen fluoride (forming hydrofluoric acid). The reaction can be summarised as: LiPF6 + 4H2O → 5HF + LiF + H3PO4. The release of HF occurs within 4 seconds in water (Unpublished stability and degradation report, 2011). HF dissociates to release F- in water, and subsequently, the lithium fluoride hydrolysis product will dissociate, releasing F- ions. Hence the toxicity of LiPF6 to terrestrial organisms is determined by the toxicities of its hydrolysis products F-, Li+ and PO4(3-). Sufficient data concerning these toxicities are available to allow determination of the environmental toxicity of LiPF6 without the performance of new tests: the available information on toxicity to mammalian and aquatic organisms clearly indicates that fluoride is the most toxic of the hydrolysis products and hence it is appropriate to focus on this to characterise the toxicity of LiPF6 to terrestrial organisms. In accordance with section 2 of REACH Annex XI, adsorption testing of LiPF6 is not technically possible due to its high reactivity and instability.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Investigation of fluoride toxicity to Gladiolus plants, using HF fumigation and inorganic fluoride administration in soil plus measurement of effects ondetached leaves
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
F- is a product of the rapid reaction of LiPF6 with water
Analytical monitoring:
no
Details on preparation and application of test substrate:
Broward soil or sand
Species:
other: Gladiolus
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
Gladiolus plants, varieties Friendship and Orange Gold
Test type:
other: investigation of leaf scorch in whole plants, stomatal opening and photosynthesis in detached leaves
Study type:
laboratory study
Substrate type:
other: natural sand (fumigation test) or soil (exposure via soil)
Remarks:
Overnight fumigation or long-term exposure via fluoride in soil; 2-6 h exposure of detached leaves
Nominal and measured concentrations:
Single concentration tested by application to soil: application rate of 81.4 kg F-/ha equates to approximately 1.46 F-/pot or 91 mg/l soil.
HF concentration for fumigation not specified. detached leaves tested in solutions of up to 10 ppm HF
Species:
other: Gladiolus sp.
Dose descriptor:
other: Effect concentration for leaf scorch
Effect conc.:
ca. 91 other: mg/l soil
Nominal / measured:
nominal
Conc. based on:
other: fluoride
Basis for effect:
phytotoxicity
Remarks on result:
other: fluoride applied to soil in superphosphate
Details on results:
Administration in soil: scorch seen towards leaf centre rather than on margins (F- applied to soil at 81.3 g/sq.m).
Administration by HF fumigation (concentrations unspecified): scorching seen typically at leaf margins.
Exposure of detached leaves/leaf discs: increased stomatal opening and (Orange Gold plant variety only) reduced photosynthesis at 10 ppm HF
Conclusions:
At the relatively high concentration tested, fluoride caused leaf scorch. The author noted that Gladiolus plants make suitable indicators for detection of atmospheric fluoride as they are highly sensitive to it.
Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
other: Information on major hydrolysis product of the registered substance (released rapidly on contact with water/moisture).
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Detailed report of field study reported in a peer-reviewed journal
Justification for type of information:
Part of weight-of-evidence approach adapting the information requirements of Annex IX 9.4.3 and Annex X 9.4.6 under REACH in accordance with Annex XI Section 1.2. Lithium hexafluorophosphate is reactive and unstable in water and air. Reaction in contact with water proceeds rapidly, with release of hydrogen fluoride (forming hydrofluoric acid). The reaction can be summarised as: LiPF6 + 4H2O → 5HF + LiF + H3PO4. The release of HF occurs within 4 seconds in water (Unpublished stability and degradation report, 2011). HF dissociates to release F- in water, and subsequently, the lithium fluoride hydrolysis product will dissociate, releasing F- ions. Hence the toxicity of LiPF6 to terrestrial organisms is determined by the toxicities of its hydrolysis products F-, Li+ and PO4(3-). Sufficient data concerning these toxicities are available to allow determination of the environmental toxicity of LiPF6 without the performance of new tests: the available information on toxicity to mammalian and aquatic organisms clearly indicates that fluoride is the most toxic of the hydrolysis products and hence it is appropriate to focus on this to characterise the toxicity of LiPF6 to terrestrial organisms. In accordance with section 2 of REACH Annex XI, adsorption testing of LiPF6 is not technically possible due to its high reactivity and instability.
Qualifier:
no guideline available
Principles of method if other than guideline:
Field study of phytotoxicity in trees growing in sites of varying distance from an industrial source of atmospheric fluoride
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
F- is a product of the rapid reaction of LiPF6 with water
Analytical monitoring:
yes
Details on sampling:
Atmospheric fluoride at test sites collected on sodium formate treated filter papers suspended on windward tree branches
Species:
other: Balsam fir (Abies balsamea)
Plant group:
Gymnospermae (conifers)
Species:
other: Black spruce (Picea mariana)
Plant group:
Gymnospermae (conifers)
Species:
other: Larch (Latrix laricina)
Test type:
other: Defoliation and needle damage, cone and seed production plus seed germination monitored
Study type:
field study
Remarks:
Atmospheric fluoride monitored over 3 months. Effects on target trees assessed at end of this period (for balsam fir, black spruce effects in pine needles assessed for current and previous year)
Species:
other: all 3 tree species examined
Duration:
3 mo
Dose descriptor:
LOEC
Effect conc.:
ca. 0.9 other: microgrammes F-/cu.m
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: atmospheric fluoride concentration
Basis for effect:
phytotoxicity
Remarks:
(visible signs)
Details on results:
In all 3 species, 100% of the trees examined at the test site farthest from the fluoride source (10.3 km) showed signs of phytoxicity; at the control site ((18.7 km from the source), 0% showed phytotoxicity. At the farthest test site, average atmospheric fluoride concentration was calculated to be approximately 0.9 microg F-/cu.m compared to 0.1 microg F-/cu.m at the control site.

The frequency of necrosis or chlorosis in pine needles was directly correlated with both atmospheric F- concentration and measured F- content of the needles (P<0.05).

Tree fertility was inversely correlated with mean atmospheric F- concentration (P<0.05):

- % fertile trees for Balsam fir and Black spruce

- cones/fertile tree for Larch

- seed germination was markedly reduced at the site closest to the fluoride source (average ca. 11.4 microg F-/cu.m) for Balsam fir and Black spruce. Here it was 27.3% and 1.4% respectively, compared to 72% and 58.3% at the control site.

Conclusions:
Atmospheric pollution from an industrial fluoride source caused evident phytotoxicity in coniferous trees: a mean annual level of 0.9 microg F-/cu.m was sufficient to cause visible damage in 100% of the trees examined.

Description of key information

Prolonged atmospheric exposure to fluoride in gaseous and/or particulate form can cause phytotoxicity in sensitive plant species.  A detailed field study of conifers growing at sites subject to atmospheric fluoride pollution found visible damage after exposure at a mean concentration of approximately 0.9 microgrammes fluoride/cu.m

Key value for chemical safety assessment

Additional information

In conifers, prolonged exposure to a fluoride concentration of 0.9 microgrammes fluoride/cu.m appeared sufficient to cause visible damage (seen as defoliation and/or pine needle necrosis/chlorosis).

Given the natural background level of fluoride present in soil (e.g. 200-700 mg/kg, reported for various soil types: HF - EU RAR, 2001), no trace quantity addition from LiPF6 use is likely to adversely affect higher plant growth.