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Section 6.1 Summary

Toxicity to freshwater organisms

Acute freshwater data:

For fish, 51 individual reliable acute toxicity data points for three different species were put forward for hazard assessment purposes. The acute toxicity values (96h-LC50) for Pimephales promelas varied between of 40.8 µg dissolved Pb/L (at pH 5.67 and hardness of 15.9 mg/L as CaCO3) and 3597.9 µg dissolved Pb/L (at pH 7.1 and hardness of 26 mg/L as CaCO3). The acute toxicity values (96h-LC50) for Oncorhynchus mykiss varied between of 127 µg dissolved Pb/L (at pH 7.6 and hardness of 32 mg/L as CaCO3) and 1470.0 µg dissolved Pb/L (at pH 8.8 and hardness of 290 mg/L as CaCO3). For the fish Poecilia reticulata a LC50 value of 1990 µg dissolved Pb/L was retreived. For invertebrates, 47 individual reliable acute toxicity data points for two different species were put forward for hazard assessment purposes. The acute toxicity values (48h-LC50) for Ceriodaphnia dubia varied between of 26.4 µg dissolved Pb/L (at pH 8.1 and hardness of 25 mg/L as CaCO3) and 3115.8 µg dissolved Pb/L (at pH 8.15 and hardness of 103.2 mg/L as CacO3). The acute toxicity values (48h-LC50) for Daphnia magna varied between of 280 µg dissolved Pb/L (at pH 7.5 and hardness of 72 mg/L as CaCO3) and 364.5 µg dissolved Pb/L (at pH 7.6 and hardness of 54 mg/L as CaCO3).

For algae, 17 individual reliable freshwater acute toxicity data points for 3 species were put forward for hazard assessment purposes. The acute toxicity values (72h-EC50) for Pseudokirchneriella subcapitata varied between of 20.5 µg dissolved Pb/L (at pH 7.6 and hardness of 24 mg/L as CacO3) and 364 µg dissolved Pb/L (at pH 6 and hardness of 24 mg/L as CaCO3). Acute toxicity calues for the freshwater alga Chlorella kesslerii (48 h EC50 of 388 µg dissolved Pb/L) and Chlamydomonas reinhardtii (48 h EC50 of 171.8 µg dissolved Pb/L). For the higher plants, the acute EC50 values for Lemna minor varied between 221.7 µg dissolved Pb/L (at pH 7.9) and 1674 µg dissolved Pb/L (at pH 7.2).

Chronic freshwater data:

A Species Sensitivity Distribution (SSD) has been developed for the assessment of lead in the freshwater compartment, using the reliable species-specific chronic toxicity effect levels that have been identified in the previous section of this report.

From the extracted data, it can be noted that the Pb database fulfils the requirement of 10-15 different NOEC values. Indeed, 180 individual high quality NOEC/EC10 values for 27 different species (fish, invertebrates, higher plants and algae) were compiled from the database. Chronic NOEC/EC10 values are available for 3 unicellular algal species, 1 higher plant (Lemna minor), 2 rotifer species (Brachionus calyciflorus; Philodina rapida), 3 insects (Baetis tricaudus; Chironomus tentans; Chironomus riparius), 3 mollusc species (Lymnaea stagnalis; Lymnaea palustris; Lampsilis silliquoidea), 5 crustacean species (Ceriodaphnia dubia; Daphnia magna; Hyalella azteca; Diaphanosoma birgei; Alona rectangula) and 10 fish species (Acipenser sinensis; Acipenser transmontanus; Cyprinus carpio; Ictalurus punctatus; Lepomis macrochirus; Pimpehales promelas; Salmo salar; Oncorhynchus mykiss; Salvelinus fontanilis; Salvelinus namaycush).

All high quality chronic data retained for PNEC derivation were normalised for bioavailability. Indeed, reports/publications reporting toxicity data as total Pb concenrations were in first instance converted to dissolved Pb concentrations using the equation generated by Blust (2014). An additional step in the bioavailability correction was introduced to normalize the dissolved chronic freshwater toxicity data towards relevant eco-regions (Dutch ditches; river Otter; river Teme; river Rhine; river Ebro; Lake Monate; Swedish acidic lake) and reasonable worst-case scenarios using the developed and validated chronic BLMs for alga (P. subcapitata), invertebrates (C. dubia), rotifer (B. calyciflorus) and fish (P. promelas).

As mentioned before, the normalised Pb toxicity data have been used for the construction of a Species Sensitivity Distribution (SSD) from which the median 5th percentile, i. e. the HC5,50% with 5%-95%-confidence interval, has been derived using best fitting distributions for all eco-regions and reasonable worst-case scenarios considered.

With due considerations of bioavailability, the resulting EU scenario specific HC5,50% range between 4.1 to 14.6 µg Pb/L when using the conventional normal distribution. The resulting EU scenario specific HC5,50% using the best fitting approach range between 4.0 and 19.4 µg Pb/L. In all cases it seems that the best fitting curve was the logistic distribution on the log-transformed toxicity data. The HC5,50% value obtained for the hypothetical reasonable worst-case scenario varied between 3.4 and 5.0 µg Pb/L using the conventional normal distribution and between 4.7 and 6.6 µg Pb/L using the best fitting (i.e. logistic) distribution. The reasonable worst case scenario resulting in the most conservative HC5,50% value is obtained at the low pH of 6.2

Application of an assessment factor between 1 and 5 on this HC5,50% will result in the final PNEC for lead in the freshwater environment. Based on the available data, the following points have to be considered when determining the size of the assessment factor:

The chronic Pb database covers only ecologically relevant endpoints. The selected endpoints were mortality, growth, hatching, reproduction and abnormalities,

The NOEC/L(E)C10 data were extracted from tests performed in a variety of natural/artificial freshwaters, covering a considerable part of the wide range of the freshwater characteristics (pH value and hardness) that are normally found in European freshwaters.

The chronic Pb database covers sensitive life stages and ‘chronic’ exposure times for all trophic levels.

The eight different trophic levels that were defined in the ECHA Guidance Document (2008) are represented in the database

From the extracted data, it seems that the Pb database do fulfill the requirement of 10-15 different NOEC values from the London Workshop. Indeed, 180 individual high quality NOEC/EC10 values and 27 different species NOEC values (fish, invertebrates, higher plants and algae) were compiled from the database.

The use of the best fitting Logistic (for the eco-regions and the reasonable worst-cases) distributions minimizes the statistical uncertainties around the HC5,50% value.

Comparison between field and mesocosm studies and the HC5,50% suggest that the HC5,50% is sufficiently protective. However, only a limited number of data are available.

The high sensitivity of laboratory Lymnaea sp. populations is confirmed as no significant difference in sensitivity towards Pb was observed compared to field populations.

However in conclusion on the subject on the choice of the assessment factor and considering all arguments above including the particular cautious approach taken for derivation of HC5,50% it is felt that the most appropriate AF would be 2. Therefore, hence the reasonable worst case freshwater PNEC is proposed to be 2.4 µg dissolved Pb/L, which will be carried over to the risk characterization.

 

Toxicity to marine organisms

A Species Sensitivity Distribution (SSD) has been developed for the assessment of lead in the marine compartment, using the reliable species-specific chronic toxicity effect levels that have been identified in the previous section of this report. In total, 59 individual high quality NOEC/L(E)C10 values and 20 different species NOEC/L(E)C10 values were compiled from the database. Chronic NOEC/L(E)C10 values are available for 3 unicellular algal species (Skeletonema costatum, Dunaliella tertiolecta, Phaeodactlylum tricornutum), 1 higher plant (Champia parvula), 3 echinoderms (Strongylocentrotus purpuratus, Dendraster excentricus, Paracentrotus lividus), 5 bivalve molluscs (Mytilus galloprovincialis, Mytilus trossolus, Perna viridis, Crassostrea gigas, Ruditapes decussatus), one annelid (Neanthes arenaceodentata), three crustaceans (Americamysis bahia, Penaeus monodon and Tisbe battagliai) and 4 fish (Mugil cephalus, Terapon jarbua, Atherinops affinis and Cyprinodon variegatus). The selected no-effect levels for dissolved lead for fish varied between 11.6 µg Pb/L (Mugil cephalus)and 437 µg Pb/L (Cyprinodon variegatus). No-effect levels for dissolved lead for invertebrates were situated between 9.2 µg Pb/L (Mytilus trossolus; endpoint: development) and 1409.6 µg Pb/L (Mytilus galloprovincialis; endpoint: mortality). No-effect levels for dissolved lead for algae/higher plants were situated between 11.9 µg Pb/L (Champia parvula; endpoint: reproduction) and 1234 µg Pb/L (Phaeodactylum tricornutum; endpoint: growth rate).

As mentioned before, the high quality dissolved Pb toxicity data have been used for the construction of a Species Sensitivity Distribution (SSD) from which the median 5th percentile, i. e. the HC5,50% with 5%-95%-confidence interval, has been derived. The generated HC5,50% value based on total/dissolved NOEC/EC10 values was 4.9 µg Pb/L (1.5-10.9 µg Pb/L) using the log-normal distribution and 6.5 µg Pb/L (3.5-13.1 µg Pb/L) using the best fitting distribution (i.e. the Rayleigh distribution). The generated HC5,50% value based on dissolved NOEC/EC10 values only was 7.5 µg Pb/L (1.8-18.5 µg Pb/L) using the log-normal distribution and 9.6 µg Pb/L (4.8-22.0 µg Pb/L) using the best fitting distribution (i.e. the Rayleigh distribution). Using both total/dissolved NOEC/EC10 values to generate the HC5,50% value for the marine environment is therefore the most conservative approach. Application of an assessment factor between 1 and 5 on this HC5,50% will result in the final PNEC for lead in the marine environment. Based on the available data, the following points have to be considered when determining the size of the assessment factor:

The chronic Pb database covers only ecologically relevant endpoints. The selected endpoints were mortality, growth, emergence, reproduction and abnormalities,The NOEC/L(E)C10 data were extracted from tests performed in a variety of natural/artificial marine waters, covering a considerable part of the wide range of the marine water characteristics (pH value and salinity) that are normally found in European coastal waters.

The chronic Pb database covers sensitive life stages and ‘chronic’ exposure times for all trophic levels.

The database includes a broad representation of temperate marine organisms, including unicellular algae, higher plants, invertebrates and fish. Indeed, 59 individual high quality NOEC/EC10 values and 20 different species NOEC values were compiled from the database.

All tests were performed in artificial test media which are considered to promote metal bioavailability (i. e., worst-case conditions) due to the absence of natural compounds in the water that can form metal complexes and, hence, reduce metal bioavailability and toxicity (e. g., dissolved organic matter);

The use of the best fitting distribution on the log-transformed toxicity data minimizes the statistical uncertainties around the HC5,50% value.

No data allowed the comparison between field and mesocosm studies and the HC5,50%.

However in conclusion on the subject on the choice of the assessment factor and considering all arguments above including the particular cautious approach taken for derivation of HC5,50% it is felt that the most appropriate AF would be 2. Therefore, hence the reasonable worst case marine PNEC is proposed to be 3.3 µg dissolved/total Pb/L, which will be carried over to the risk characterization.

Toxicity to micro-organisms in sewage treatment systems

The bacterial studies including single-species tests and mixed-population tests (e.g. activated sludge, respiration inhibition tests), resulted in toxicity values for microbial degradation in STP, e.g. sludge with inhibition of respiration and nitrification as endpoints, ranging from 1.06 mg/L to 9.59 mg/L Pb. The protozoan tests resulted in L(E)C50 values ranging from <1.5 mg/L (LC50 for different ciliate species) to >250 mg/L (LC50 for Tetrahymena pyriformis).

The lowest observed NOEC value for inhibition of nitrification using activated sludge was 2.79 mg/L dissolved Pb. The lowest observed NOEC value for inhibition of respiration was 1.06 mg/L dissolved Pb. The lowest observed bounded EC50 value from tests with other ciliated protozoa tested in activated sludge mixed liquor medium is 2.29 mg Pb/L (for ciliate Vorticella convallaria). On the other hand, a (visually) derived LC10 for the sludge protozoan community in the activated sludge mixed liquor of 1 mg/L dissolved Pb is estimated. Preference was given to this community endpoint because it is more relevant.

Based on the above reported results and discussion at TCNES II 07 a preference was expressed for application of an assessment factor of 10. In this case, a PNEC for micro-organisms of 0.1 mg/Lfor dissolved lead in effluent is calculated and, at the request of TCNES, this is the value forwarded to risk characterisation. Note that there are insufficient useful data for aquatic micro-organisms to apply statistical extrapolation.

Toxicity to freshwater sediment organisms

Toxicity data for Pb to sediment organisms are summarized in the voluntary risk assessment of lead (LDAI, 2008). For lead a complete set of freshwater sediment effects data is available for the sediment compartment with 7 NOEC values for 7 different species (Tubifex tubifex, Ephoron virgo, Hyalella azteca, Gammarus pulex, Lumbriculus variegatus, Hexagenia limbata and Chironomus tentans). The chronic no-effect toxicity values for the freshwater sediment-dwelling organisms varied between 577 and 3390 mg/kg dw.

Therefore, similar to what has been agreed for the nickel and copper risk assessments it is appropriate to evaluate the benefits of estimating the PNEC for sediment by using the available toxicity sediment toxicity tests and applying the statistical extrapolation methodology, the median fifth percentile (HC5 -50) of the best fitting species sensitivity distribution has been calculated. Using the software package ETx, the Log-Normal Distribution was selected. The HC5-50 for total Pb in freshwater sediment was 522 mg/kg dw.

 

Application of an assessment factor between 1 and 5 on this HC5-50 will result in the final PNEC for lead in the freshwater sediment. Based on the available data, the following points have to be considered when determining the size of the assessment factor:

- The chronic Pb database covers only ecologically relevant endpoints. The selected endpoints were mortality, growth, emergence, reproduction and biomass,

- The chronic Pb database covers sensitive life stages and ‘chronic’ exposure times for all trophic levels.

- High quality chronic L(E)C10/NOEC values are available for 7 different sediment-dwelling invertebrates, belonging to 3 different families (i.e. oligochaetes, crustaceans and insects) with different feeding habits and ecological niches,

- The use of the best fitting Log-Normal distribution minimizes the statistical uncertainties around the HC5-50 value.

- No data allowed the comparison between field and mesocosm studies and the HC5-50.

However in conclusion on the subject on the choice of the assessment factor and considering all arguments above including the particular cautious approach taken for derivation of HC5-50 it is felt that the most appropriate AF would be 3. Therefore, hence afreshwater sediment PNEC is proposed to be 174 mg Pb/kg dw, which will be carried over to the risk characterization.

In addition, a freshwater sediment PNEC corrected for bioavailability has been calculated. Since AVS is a determining factor in controlling lead toxicity in sediments a bioavailable PNEC (corrected for AVS) has also been derived. In the VRAR of lead (2008) the statistical distribution method has been used to derive a PNEC bioavailable of 81 mg/kg dry wt. However, since some datapoints included in the SSD were derived from actual LOEC values SCHER recommended the use of the classical AF factor approach applying a factor of 10 to the lowest unbounded bioavailable NOEC. In this case the lowest NOEC was 2.0 µmol excess Pb/g dw, resulting in a bioavailable freshwater sediment PNEC of 0.2 µmol excess Pb/g dry wt or 41 mg Pb/kg dw

Toxicity to marine sediment organisms

EC10/NOEC values (total Pb) for lead are available for two marine sediment-dwelling organisms. These NOEC/L(E)C10 values cover different habitats and feeding behaviors and varied between 680 and 1281 mg/kg dw.To calculate the PNEC for the marine sediment compartment, the long term marine and freshwater sediments effect data are pooled in a common dataset resulting in 9 EC10/NOEC values for 9 different sediment-dwelling species. Therefore the PNEC for marine sediment was estimated by using the available freshwater and marine toxicity sediment toxicity tests and applying the statistical extrapolation methodology.

Using the software package ETx, the Log-Normal Distribution was selected. The HC5-50 for total Pb in marine sediment was 492.5 mg/kg dw.

Application of an assessment factor between 1 and 5 on this HC5-50 will result in the final PNEC for lead in the marine sediment. Based on the available data, the following points have to be considered when determining the size of the assessment factor:

- The pooled chronic Pb database covers only ecologically relevant endpoints. The selected endpoints were mortality, growth, emergence, reproduction and biomass,

- The chronic Pb database covers sensitive life stages and ‘chronic’ exposure times for all trophic levels.

- High quality chronic L(E)C10/NOEC values are available for 9 different sediment-dwelling invertebrates, belonging to 3 different families (i.e. oligochaetes, crustaceans and insects) with different feeding habits and ecological niches,

- The use of the best fitting Log-Normal distribution minimizes the statistical uncertainties around the HC5-50 value.

- No data allowed the comparison between field and mesocosm studies and the HC5-50.

However in conclusion on the subject on the choice of the assessment factor and considering all arguments above including the particular cautious approach taken for derivation of HC5-50 it is felt that the most appropriate AF would be 3. Therefore, hence a marine sediment PNEC is proposed to be 164.2 mg Pb/kg dw, which will be carried over to the risk characterization.