Slags, steelmaking

Long-term toxicity to aquatic invertebrates

Description of key information

Read across from laboratory studies e. g.
ABS: Daphnia magna OECD 211: 21d-EC10 = 5000 mg/L
Field studies see Discussion

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

5 g/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

0.5 g/L

Additional information

Laboratory studies

To determine the chronic ecotoxicity of ferrous slags on invertebrates under GLP guideline conditions in the laboratory, slags, ferrous metal, blast furnace (air cooled – ABS) were tested for their effects on reproductive output of Daphnia magna according to C.20 Daphnia magna reproduction test of the EU-regulation 440/2008. Female Daphnia (the parent animals) aged less than 24 h at the start of the test were exposed to the slags at six nominal concentrations for 21 days. The reproductive output of the animals exposed to the different concentrations of the slags was compared to that of the controls in order to determine the lowest observed effect concentration (LOEC) and the no observed effect concentration of the slags (NOEC).

The following nominal effect concentrations were found after 21 d of incubation: 

• Mean cumulative offspring of survivors EC₁₀> 5000 mg/L
• Age of first reproduction > 5000 mg/L¹
• Mobility NOEC = 1563 mg/L
• Intrinsic rate NOEC = 488.3 mg/L
• Intrinsic rate LOEC > 1563 mg/L
• Intrinsic rate EC₁₀= 5000 mg/L
• Size of the parent animals at test end EC₁₀≥5000 mg/L 

(SGS Fresenius 2010).

In a chronic toxicity test according to the French guideline "Test de toxicité chronique - Ceriodaphnia dubia à 7 jours. Rapport des essais inter-laboratoires" (1995), neutralized leachate of ABS (L/S 10/1) was not toxic to Ceriodaphnia dubia. In regard to reproduction, the NOEC was 10 g/L (nominal), and the LOEC was 20 g/L after 7 days. In regard to mortality, the NOEC was 50 g/L, and the LOEC was 70 g/L after 7 days (LECES 1991).

In EAF C leachate prepared in bidistilled water, with high pH, population densities of Hydra were lower than in controls with almost neutral pH. Undiluted leachate with a final pH of 11.5 decreased number of Hydra individuals by 80 % within one day but population size recovered within further 9 days to approximately half of the population size of the controls. Undiluted, neutralized EAF C leachate did not inhibit growth of Hydra littoralis ( 10 d-NOEC >= 100 g/L nominal) suggesting that any effect of slag leachate on population growth of Hydra is due to pH. Leachates prepared in Elbe water were more inhibitory for these freshwater organisms than leachates prepared in bidistilled water presumably due to elevated concentrations of chlorides or other salts (Karbe and Ringelband 1996).

In EAF C leachate with high pH, population densities of the hydrozoan Cordylophora caspia were lower than in controls with almost neutral pH. Undiluted leachate with a final pH of 11.5 inhibited increase of Cordylophora populations by approximately 30 % within 10 days. Undiluted, neutralized EAF C leachate did not inhibit population growth of Cordylophora caspia (10 d-NOEC >= 100 g/L nominal) suggesting that any effect of slag leachte on Cordylophora population growth is due to pH (Karbe and Ringelband 1996).

Field studies

The long-term effect of slag used for embankment on the aquatic environment was tested by monitoring the macrozoobenthic populations on the surface of slag (ABS) and basalt forf 13 years. The macrozoobenthos populations were very similar on basalt and on slag:

• Basalt/natural stone 9 species and 2965 individuals
• Slag: 11 species and 3093 individuals

Basalt and slag are eqaully well suited - in regard to number of species (diversity) and number of individuals (abundance) - as a substrate for growth of sessile invertebrate populations (BfG 1986).

In a non-guideline large-scale field study slags, steelmaking, converter (BOS), basalt and greywacke placed in the river for at least 5 years, were taken from the river Rhine and analyzed for population by macroinvertebrates. The size and diversity of the macroinvertebrate populations on both natural stones (basalt and greywacke) and slag (BOS) were extremely similar. The faunistical settlement within the river bank on the slag was richer in species and individuals than on the natural stones. This finding was ascribed to the more coarse surface of slags compared to the more plain surface of the greywacke. This finding was ascribed to the more coarse surface of slags compared to the more plain surface of the greywacke. The benthic habitat of the interstitial is affected less by the origin or composition the stones, but rather by the portion of the small grain-sized material.

Trace elements (e. g. Hg, Cd, Pb, Zn, Cu, and Ni) are present in BOS only in very small concentrations. A (re) mobilisation of these elements was not observed, and no effects of these elements could be detected in the population structure and density of the macroinvertebrates (Bundesanstalt fuer Gewaesserkunde 1986)

The long-term effect of slag on the aquatic environment was tested by monitoring the macrozoobenthic populations on the surface of slag (ABS) and diabase in the River Elbe in.

The macrozoobenthos populations were very similar on diabase and on slag. Diabase and slags are eqaully well suited - in regard to number of species (diversity) and number of individuals (abundance) - as a substrate for growth of sessile invertebrate populations. No inhibitory effect of slag could be detected (Krueger 1994).

The colonization of EAF C and natural rock fields on banks of theriver by sessile animal populations was examined qualitatively and quantitatively in field experiments with diabase and EAF C. First colonization of newly dumped stones occurs in the lower part of the stone fields because these parts are longer covered by water than the upper parts of the (tidal) stone fields. The colonization of the newly dumped stones (diabase and EAF C) was very inhomogeneous and there were conflicting trends, but there were no relevant differences in the colonization of natural rock (diabase) and slag (EAF C) by aquatic animals. No toxic effect is exerted by EAF C (Karbe and Ringelband 1996).

The colonization by sessile organisms of EAF C and natural rock exposed in baskets to theriver water was examined qualitatively and quantitatively in field experiments. The colonization by invertebrates of the solid matrial introduced into the watercouses was much more slowly than the settlement and growth of autotrophic organisms. During both test years EAF C was colonized at approximately the same velocity and manner as the natural rocks. Use of EAF C in watercourses with continuous water exchange will not significantly affect the growth of sessile organisms. Use of EAF C in watercourses without continuous water exchange may affect the primary population of these materials within the first 8 weeks. After this period, no differences in algal densities are expected but differences in the composition of sessile populations may occur at such sites. No toxic effect is exerted by EAF C (Karbe and Ringelband 1996).