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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Very complete and well documented study that gives proper information on the potential consequences of an accidental spill in standing waters.
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
Mecocosm study.
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Concentration in water lower or close to detection limit level (~0.005 mg/l) throughout the study period. Approximately 100% of the substance was found in the sediment as hardened material at the end of the study period.
Details on test solutions:
Substance added directly onto the bottom of the ponds with a hose.
Test organisms (species):
other: other aquatic plant: macrophytes
Details on test organisms:
macrophytes (Potamogeton crispus and Zannichellia palustris).
Test type:
other: mecocosm
Water media type:
freshwater
Total exposure duration:
112 d
Post exposure observation period:
Test parameter: fluctuations of biomass.
Hardness:
Measurements were taken at approximately every 2 weeks.

Overall the control pond had a hardness of about 4°dH (corresponding to about 40mg CaO/l) and remained fairly steady throughout the study period. Following production of carbon dioxide from applied PMDI, results from the treated ponds showed a dose related increase of hardness. Values as high as approximately 10°dH were obtained at the end of the study period for the high dose pond.
Test temperature:
During the first days after application, temperature was measured two to three times a day and thereafter several times a week. The temperature fluctuated between 18 and 23°C. In general there were no differences between the three ponds during the entire study period.
pH:
During the first days after application, pH was measured two to three times a day and thereafter several times a week. The pH of the control pond typically ranged, on average, from approximately pH8 to pH9. The pH of the high dosed pond rapidly declined following application and overall the pH of this pond was approximately 2.0 units lower on average than in the control pond. The pH of the low dosed pond was slightly lower than in the control pond for the whole study.
Dissolved oxygen:
During the first days after application, dissolved oxygen was measured two to three times a day and thereafter several times a week. Dissolved oxygen varied between 9 and 22mg/l, values indicating high productivity of the phytoplankton and macrophytes which result in concentrations well above the oxygen saturation at these temperatures. Up to approximately 25 days the oxygen concentrations in all three test ponds corresponded very well. Thereafter oxygen concentrations in the treated ponds were higher than those in the control pond.
Nominal and measured concentrations:
1000 and 10000 mg/l
Details on test conditions:
Three 4.5 m3 ponds filled with groundwater and added natural lake sediment (15 cm); the systems were left outdoors for six months. Links between ponds were then closed; fish were added to ponds (in cages) and substance added to two ponds at two different concentrations (1000 and 10 000 mg/l), the last one being the control.
Reference substance (positive control):
not specified
Duration:
112 d
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: Biomass was significantly higher in the presence of MDI (42% higher in the high-dosed pond and 14 % in the low -dosed pond) due to increased CO2 in the water.

Although macrophyte abundance was severely affected in the treated ponds because of physical obstruction, their biomass was significantly higher in the presence of MDI (42% higher in the high-dosed pond and 14 % in the low -dosed pond) due to increased CO2 in the water.

Conclusions:
MDI applied polymerized and formed a stable layer on the sediment surface of the ponds. At the end of the study, approximately 100% of the substance was found in the sediment as hardened material.

Description of key information

Not required by REACH annexes. However, a mesocosm study (Heimbach, 1993) with PMDI exists in which the toxicity towards macrophytes

(Potamogeton crispus and Zannichellia palustris) was assessed. No toxicity was observed at a loading of 1000 and 10,000 mg/L.

Key value for chemical safety assessment

Additional information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). Hence, data of the category substances can be used to cover this endpoint. The read-across category justification document is attached in IUCLID section 13. It is important to note that the MDI category approach for read-across of environmental and human hazards between the MDI substances belonging to the MDI category is work in progress under REACH. Therefore the read-across document should be considered a draft.

In a mesocosm study, a pond was exposed to a loading of 1000 and 10,000 mg/L of PMDI during 112 days. Three 4.5 m3 ponds were filled with groundwater and added natural lake sediment (15 cm). The systems were left outdoors for six months. Links between ponds were then closed; fish were added to ponds (in cages) and substance added to two ponds at two different loadings (1000 and 10,000 mg/L). The third pond was the control. The substance was added directly onto the bottom of the ponds with a hose. The toxicity effects were assessed to two macrophytes, Potamogeton crispus and Zannichellia palustris. No effects were seen at both loadings. The MDI applied polymerized and formed a stable layer on the sediment surface of the ponds. At the end of the study, approximately 100% of the substance was found in the sediment as hardened material.