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Toxicity to soil microorganisms

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Description of key information

Several studies investigating the toxicity of Ni to soil microorganisms were identified as key studies, and used for derivation of the HC5 and terrestrial PNEC. The lowest NOEC was 32 mg Ni/kg dw. 

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
32 mg/kg soil dw

Additional information

Tests on microbial processes are multi-species tests, in which the native soil microbial community is exposed. The selected NOEC or EC10values comprise functional parameters (n=39), and microbial species (n=13). The functional parameters are based on the carbon cycle (n=27), nitrogen cycle (n=12), including denitrification and mineralization of specific substrates. Enzymatic parameters are also further considered in the effects assessment. Different enzymatic processes were compiled in the database. In the total risk approach, NOEC or EC10values range from 28 mg/kg (nitrification mineralisation; Smolders, 2000) to 2491 mg/kg (respiration; Doelman & Haanstra, 1984). Additional data are available for enzyme activity measured in soil, with NOEC/EC10values ranging from 7.9 mg Ni/kg for dehydrogenase to 7084 mg Ni/kg for arylsulfatase activity. Finally, NOEC values for a range of Eubacteria, actinomycetes, yeasts, and filamentous fungi are also reported, and these values range from 32 mg Ni/kg forAspergillus niger(Babich and Stotzky, 1982) to 550 mg Ni/kg forTrichoderma viride(Babich and Stotzky, 1982).


 


Below are the accepted high quality studies for soil microorganisms used for derivation of the HC5 and terrestrial PNEC.





























































































































































Key Study


(Soil micro-organisms)



Selected values for the most sensitive endpoints used for derivation of the terrestrial HC5



Measurement



Added NOEC or EC10 (mg/kg dw)



Total NOEC or EC10 (mg/kg dw)



University of Leuven, 2005



Glucose respiration



45-376



56-415



Maize respiration



42-446



43-479



Babich & Stotzky, 1982b



Aspergillus flavipes (hyphal growth)



347



367



Aspergillus flavus (hyphal growth)



393



413



Aspergillus clavatus (hyphal growth)



13



32



Aspergillus(hyphal growth)



400



420



Penicillium vermiculatum (hyphal growth)



102



121



Rhizopus stolonifer (hyphal growth)



288



308



Trichoderma viride (hyphal growth)



530



550



Gliocladium sp. (hyphal growth)



200



220



Serratia marcescens (colony count)



155



174



Proteus vulgaris (colony count)



15



35



Bacillus cereus (colony count)



285



305



Nocardia rhodochrous (colony count)



177



197



Rhodotorula rubra (colony count)



247



266



Doelman & Haanstra, 1984



Respiration (CO2 release)



291-2542



295-2491



Saviozzi et al., 1997



Respiration (CO2 release)



27



41



Wilke 1988



ATP content



77



86



Haanstra & Doelman, 1984



Glutamate respiration (C02)



55



63-94



Doelman & Haanstra, 1986



Urease



90-2300



128-2302



Doelman & Haanstra, 1989



Phosphatase



251-7021



276-7023



Doelman & Haanstra, 1991



Arylsulfatase



272-7080



311-7084



Welp, 1999



Dehydrogenase



7.9



27.3



Wilke, 1988



Saccharase



77



86



Protease



77



86



Smolders, 2000



N-mineralisation



20-257



28-265



 


 


There is some activity derived also from the presence of fluoride. However, the report issued by the Commission (SCHER 2010, Critical review of any new evidence on the hazard profile, health effects, and human exposure to fluoride and the fluoridating agents of drinking water) about the addition of fluoride in drinking water clearly states that "Exposure of environmental organisms to levels of fluoride as used in fluoridation of drinking waters are not expected to lead to unacceptable risks to the environment."


 


CONCLUSION: NOEC 32 mg/Kg dw Ni2+ (= 52.7 mg/Kg dw NiF2)

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