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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

In accordance with the EU risk assessment, and in a same approach as for aquatic ecotoxicity, the soluble zinc ion is considered as the toxic entity for zinc substances in this section on soil. Consequently, the analysis below is relevant for all zinc compounds.

It is noted that the scope of the terrestrial effect assessment under REACH is restricted to soil organisms in a narrow sense, i.e., non-vertebrate organisms living the majority of their lifetime within the soil and being exposed to substances via the soil pathway. Reliable chronic toxicity data are available for the long-term effect of zinc on 35 terrestrial species or microbial endpoints covering the 3 trophic levels (12 terrestrial plants, 10 invertebrates and 13 microbial endpoints). A total of 220 reliable EC10 and NOEC values, ranging between 31.2 and 8003.5 mg Zn/kg dry weight (dw), were selected for derivation of a PNEC value. All results were derived for soluble zinc substances (Zn(CH3COO)2, ZnCl2, Zn(NO3)2 or ZnSO4, including hydrated forms).

The bioavailability and toxicity of zinc to soil organisms was significantly affected by the equilibration time and the properties of the soils tested. Toxicity to soil organisms decreased with longer equilibration time, showing lower toxicity in field conditions compared to standard laboratory settings. Toxicity to terrestrial plants decreased with higher effective cation exchange capacity (eCEC = CEC at pH of the soil) and higher pH of the soil. Toxicity to terrestrial invertebrates decreased with higher eCEC and toxicity to microbial endpoints decreased with higher background Zn concentrations in soil. Toxicity data were only considered reliable and useful for derivation of a PNEC value when information was available on the relevant soil properties of the test soil, allowing normalization of the EC10 and NOEC. Geometric mean values were derived for the most sensitive endpoint per species or microbial process in case multiple data were available for one species or process. Species or process geometric mean values without correction for bioavailability vary between 37 mg Zn/kg for reproduction of the invertebrate Enchytraeus doerjesi and 1246 mg Zn/kg for microbial dehydrogenase activity. After correction for differences between lab and field conditions and normalization to the same soil properties of an example reference soil with pH 6, 2% organic carbon, 10% clay, eCEC of 10 cmolc/kg and 25 mg Zn/kg, species or process mean values vary between 79 mg Zn/kg for reproduction of the invertebrate Enchytraeus doerjesi and 8948 mg Zn/kg for microbial dehydrogenase activity.

 

Table1. Overview of the selected chronic soil toxicity values for zinc selected forthePNEC derivationfor toxicity of inorganic zincto terrestrial organisms (based on total Zn concentrations).

Test organism

Taxonomic group

Endpoint

Original NOEC or EC10values, not corrected for bioavailability

(mg Zn/kg dw)

NOEC or EC10values corrected for differences between laboratory and field conditions and normalized to the same soil properties*

(mg Zn/kg dw)

 

 

Range (and amount)

Species or process mean

Range (and amount)

Species or process mean

Plants

Allium cepa

Amaryllidaceae(monocotyledon)

Yield

220 (n=1)

220

328 (n=1)

328

Avena sativa

Poaceae(monocotyledon)

Grain yield

238 – 702 (n=4)

374

447 – 1983 (n=4)

1046

Brassica rapa

Brassicaceae(eudicotyledon)

First bloom

546 – 549 (n=2)

547

341 – 594 (n=2)

450

Cucumis sativus

Cucurbitaceae(eudicotyledon)

Shoot yield

179 – 5213 (n=10)

782

326 – 7953 (n=10)

1650

Hordeum vulgare

Poaceae(monocotyledon)

shoot yield

91 (n=1)

91*

201 (n=1)

201

root elongation

937 – 1900 (n=3)

1453

419 – 818 (n=3)

548

Populus trichocarpa

Salicaceae(eudicotyledon)

root yield

272 (n=1)

272

571 (n=1)

571

root elongation

105 (n=1)

105*

219 (n=1)

219

Lycopersicon esculentum

Solanaceae(eudicotyledon)

shoot yield

174 (n=1)

174

189 (n=1)

189

root yield

161 (n=1)

161*

174 (n=1)

174

Trifolium pratense

Fabaceae(eudicotyledon)

shoot yield

40 – 135 (n=6)

65

111 – 335 (n=6)

259

root yield

40 – 115 (n=6)

58*

111 – 335 (n=6)

227

Trigonella foenum graceum

Fabaceae(eudicotyledon)

yield

150 (n=1)

150

217 (n=1)

217

Triticum aestivum

Poaceae(monocotyledon)

shoot yield

245 – 5925 (n=14)

612

528 – 16769 (n=14)

1950

grain yield

96 – 4779 (n=11)

574

267 – 3187 (n=11)

556

biomass yield

56 – 2835 (n=8)

362*

105 – 1099 (n=8)

346

Vicia sativa

Fabaceae(eudicotyledon)

shoot yield

108 (n=1)

108

327 (n=1)

327

root yield

40 (n=1)

40*

111 (n=1)

111

Zea mays

Poaceae(monocotyledon)

shoot yield

253 – 578 (n=2)

382

887 – 908 (n=2)

898

Invertebrates

Aporrectodea caliginosa

Lumbricidae(annelida)

reproduction

302 – 584 (n=2)

420*

352 – 643 (n=2)

476

mortality

1425 (n=1)

1425

4034 (n=1)

4034

Eisenia andrei

Lumbricidae(annelida)

reproduction

431 (n=1)

431

947 (n=1)

947

Eisenia fetida

Lumbricidae(annelida)

reproduction

99 – 1341 (n=30)

306*

255 – 1759 (n=30)

719

growth

439 – 736 (n=3)

561

1078 – 1611 (n=3)

1255

mortality

752 – 932 (n=3)

808

1570 – 2041 (n=3)

1809

Enchytraeus albidus

Enchytraeidae(annelida)

reproduction

90 – 182 (n=3)

130

137 – 398 (n=3)

252

Enchytraeus doerjesi

Enchytraeidae(annelida)

reproduction

32 – 47 (n=3)

37

69 – 103 (n=3)

79

Lumbricus rubellus

Lumbricidae(annelida)

reproduction

461 (n=1)

461

575 (n=1)

575

Lumbricus terrestris

Lumbricidae(annelida)

reproduction

442 (n=1)

442

533 (n=1)

533

Folsomia candida

Isotomidae(arthropoda)

reproduction

31 – 1261 (n=22)

261

115 – 3055 (n=22)

579

Proisotoma minuta

Isotomidae(arthropoda)

reproduction

217 (n=1)

217

1906 (n=1)

1906

Sinella curviseta

Entomobryidae(arthropoda)

reproduction

217 (n=1)

217

282 (n=1)

282

Microorganisms

Natural soil microbial communities

nitrogen transformation

ammonification

1057 (n=1)

1057

1594 (n=1)

1594

nitrogen transformation

denitrification

84 (n=1)

84

102 (n=1)

102

nitrogen transformation

nitrification

77 – 697 (n=19)

179

101 – 955 (n=19)

284

carbon transformation

acetate mineralization

346 (n=1)

346

628 (n=1)

628

carbon transformation

glutamic acid induced respiration

53 – 494 (n=5)

126

91 – 585 (n=5)

208

carbon transformation

glucose induced respiration

41 – 1393 (n=16)

269

182 – 3075 (n=16)

486

carbon transformation

mineralization of dissolved organic carbon

89 – 198 (n=4)

130

134 – 346 (n=4)

213

carbon transformation

basal respiration

55 – 313 (n=4)

167

278 – 1179 (n=4)

557

carbon transformation

maize residue mineralization

56 – 1144 (n=11)

249

64 – 1393 (n=11)

324

enzyme activity

arylsulphatase

120 – 8004 (n=5)

862

188 – 5798 (n=5)

1177

enzyme activity

dehydrogenase

1246 (n=1)

1246

8948 (n=1)

8948

enzyme activity

phosphatase

387 – 2727 (n=3)

1128

130 – 5443 (n=3)

1238

enzyme activity

urease

84 – 689 (n=2)

241

296 – 352 (n=2)

323

* pH 6, 2% organic carbon, 10% clay, eCEC 10 cmolc/kg and 25 mg Zn/kg

 

Additional information

A quality-screened database on the toxicity of zinc towards soil organisms has been compiled from the Zn RAR (Munn et al. 2010. European Union Risk Assessment Report - Zinc Metal. EUR 24587 EN. Luxembourg (Luxembourg): Publications Office of the European Union. JRC61245. https://op.europa.eu/en/publication-detail/-/publication/111d589d-8f52-442e-8720-c0ed745d2ed3/language-en) and updated with newly retrieved literature data (search 1995-2019). A total of 220 reliablechronic EC10 and NOEC values, ranging between 31.2 and 8003.5 mg Zn/kg dry weight (dw), were selected for derivation of a PNEC value. Reliable chronic toxicity data are available for the long-term effect of zinc on 35 terrestrial species or microbial endpoints covering the 3 trophic levels (12 terrestrial plants, 10 invertebrates and 13 microbial endpoints). Bioavailability corrections for zinc to soil organisms were derived from comprehensive research projects, where various toxicity assays were performed in a range of soils after various spiking treatments. The bioavailability corrections were discussed, agreed and applied in the EU risk assessment on zinc and 5 zinc compounds (Munn et al 2010).

 

Since the available ecotoxicity database for the effect of Zn to soil organisms is large, the use of the statistical extrapolation method is preferred for PNEC derivation. Based on an uncertainty analysis, and in particular the large toxicity database covering a representative range in plant and invertebrate species, microbial processes and soil conditions, the availability of normalization models, an extensive field validation, and the inherent conservatism resulting from the setting of the HC5,50%value with reference to realistic worst-case conditions of bioavailability (10th percentile of normalized HC5,50% values for 4130 soils representative for Europe), it can be concluded that the available database and models allow for the derivation of an HC5,50% that is protective for the terrestrial environment. The application of an AF = 1 is therefore proposed on the HC5,50% for the derivation of a robust and ecological relevant PNEC to be retained for the risk characterization.

 

The reasonable worst-case PNECsoil, based on the 10th percentile of the distribution of normalized HC5,50% values for an extensive, representative dataset of European soils, is 83.1 mg Zn/kg. If information on specific soil type and soil conditions is available, a soil-specific PNECsoil can be calculated, by applying the bioavailability corrections depending on soil properties. To this end, a tool is available that includes all data and bioavailability corrections for Zn, allowing derivation of site-specific PNEC values taking into account the local soil properties (https://www.arche-consulting.be/tools/threshold-calculator-for-metals-in-soil/).

For more information, see the background document on environmental risk assessment of zinc in soil, attached to section 13 of IUCLID.