Nickel difluoride

Toxicity to soil microorganisms

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)