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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

Slag stones do not exhibit any hazardous effect on any stage of early fish development e.g. fertilization of eggs, egg number, egg distribution, development of larvae.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
500 g/L
EC10, LC10 or NOEC for marine water fish:
50 g/L

Additional information

A field study was conducted in the Nord-Ostsee-Channel to elucidate the effects of stones of slag and natural rock on the reproduction of the herring, Clupea harengus. This channel is a significant spawning ground of herring, and every year approximately 15 millions of adult fish enter the channel for reproduction. The estimated number of eggs is approximately 230000 eggs/m2 of stone field, which equals approximately 83 billions of eggs in the channel (30 km length of embankment protected with stones, width 6 m). The eggs are deposited above the stone fields, sink to the ground and attach to the stones and the filamentous algae growing on these stones.

From the egg distribution data, it was apparent that herring does not prefer to slag the natural rocks basalt, granite, and diabase as a spawning ground.

The oxygen concentration of egg layers on hard ground (independent on the nature of the stones - slag or natural rocks) was close to saturation level (104 +/- 2 % of saturation, approximately 8 mg/L, depending on e.g. temperature and salinity).

The fertilization rate of eggs was independent from the nature of the stone fields and there was no difference between slag stone fields and the control fields of basalt, granite, and diabase (almost complete fertilization, at least 98.7 %)

The viability of the eggs was determined from the heartbeat of the developping larvae. Almost all larvae in the eggs deposited on hard ground had a normal heartbeat (at least 98.3 %). Concomitantly, no deviations from normal development were observed (Kils 1992).

From the observations of Kils, a (chronic) NOEC can be estimated. As the exchange rate of the brackish water is low in the channel, the hight of the water column (assumed to be 2.4 m in the slag fields) and the thickness of the slag layers (assumed to be 40 cm) were directly compared. Using a density of 3 for the slags, the estimated chronic NOEC (nominal) is approximately 12 kg/24 L = 500 g/L for weathered slags in brackish water.