11 MAY 2010

UPDATED BRIEFING PAPER ON

ZINC IN EUROPEAN WATERS

KEY INFORMATION OF RELEVANCE

TO PRIORITISATION UNDER

THE WATER FRAMEWORK DIRECTIVE

TABLE OF CONTENTS

page

  1. Summary...... 3
  1. Outcome of the EU risk assessment on zinc and the related

EU risk reduction Strategy...... 4

  1. Recent monitoring data on zinc in EU waters, and updated

risk assessment...... 5

  1. Analysis of country data...... 8

4.1. Total zinc concentrations measured in waters of

EU member states...... 8

4.2. Dissolved zinc concentrations measured in waters in EU

Member States...... 11

  1. Conclusions...... 13
  1. References...... 14
  1. Annexes...... 14

1Comments on the data compilation of the International

Office of Water, contained in the Fact sheet on zinc...... 14

2Comments on the document from the International

office of water: “Zinc data: specific data treatments”...... 15

3Response to the comments of the Netherlands

(March 30, 2010) ...... 16

1 Summary

Zinc was not identified as a substance of concern based on the monitored data recently reported to the Commission by the EU member states.

Yet, zinc is included in the shortlist of substances for further consideration into the revision of the list of priority substances under the water framework directive (WFD), based on the outcome of the EU risk assessment (completed according to 793/93/EEC, May 2008).

In the EU risk assessment (RA), a conclusion of risk was reached based on local exceedance of the PNEC in some EU waters, as observed in monitored data from before the year 2000.

The EU RRS (Risk Reduction Strategy) did not recommend to include zinc directly into the list of priority substances under the WFD. Instead, it explicitly requested an update of the monitored information used in the risk assessment, before considering zinc for prioritisation under the WFD. The recent reporting by the member states of extensive post-2000 monitored data has answered that requirement.

On the basis of the evidence made available by the member states in the ongoing discussion process the most reliable 90th percentile (90P) PEC from this update for the EU overall is lower than the PNEC (PEC/PNEC risk ratio <1; assessment according to the principles and reference values of the EU risk assessment).

On a more detailed, country-specific level, the updated monitored data show:

1)that none of the countries, figuring in the EU risk assessment, still shows a risk for zinc (NL, B, D, F, UK).

2)that in all other EU countries that have submitted data that is relevant for this evaluation, there is no risk observed. This recent update of the monitored zinc levels in the EU, with information from 19 EU member states thus demonstrates that there is no risk for zinc across the EU. In the few countries where a risk ratio > 1 was reported, further investigation has revealed that the monitoring data was intentionally focused on point sources and that the underlying reasons for elevated zinc levels in these countries have been identified as being specific and local (e.g. as being related to historical contamination from abandoned mining sites). As concluded by the 2008 EU Risk Reduction Strategy for Zinc, such local exceedances should be addressed at the national level, by treating zinc as a specific pollutant (Annex VIII) under the WFD.

The legally required update of the monitored data thus shows that there is no widespread risk for zinc in EU waters, and that the outcome of the risk assessment is no longer a basis for prioritisation of zinc under the WFD.

In conclusion, there are no elements justifying prioritisation of zinc under the WFD. Where needed, zinc should be addressed at national level as a specific pollutant, its present status under the WFD.

2 Outcome of the EU risk assessment on zinc and the related EU risk reduction strategy

The EU RA made an extensive analysis of the risks of zinc to EU waters, based on:

-modelling of the very detailed emission data available on zinc and compounds (including diffuse emissions from zinc products). According to this analysis, there were no risks related to zinc at the regional level.

-monitored data from a few member states, all dating from before the year 2000. Based on this analysis, it was concluded that there was a regional risk, because of local exceedances of PNEC in a number of waters: “measured surface water concentrations indicated that the PNECadd,water is exceeded in some, but not all, regional waters in the EU (conclusion iii)”(RA, ECB 2008).

-in addition to this regional conclusion, a number of local risks were identified for water, related to local emissions by zinc producing or processing industry.

Considering these RA conclusions, an EU risk reduction strategy was developed by the Rapporteur country (The Netherlands) and approved by the member states. Related to the ongoing discussion on the revision of the priority substances for the WFD, the following points of the EU RRS discussion and conclusions are relevant:

-it was decided not to recommend prioritisation of zinc, because of the recognised local character of the zinc risk to water, and the different underlying reasons for PNEC exceedance.

-information generated at the end of the RA-process and contained in Annex to the risk assessment report, demonstrated that the observed exceedances of PNEC were primarily due to point source emission and historical contamination, and that zinc products were not the main source of the exceedances (“The findings of this report are that the current uses of zinc and zinc compounds do not per se leadto the elevated regional levels found in surface water and sediment” - RA, ECB 2008). This was recognised in the EU RRS that did not formulate any measures against zinc use in products, but recommended specific attention on EU legislation to control point sources, through the IPPC directive (OJ 2008). It was also noted in the RRS process that WFD objectives for zinc could be met through its status as a specific pollutant (ie an Annex VIII substance).

-recognising also the progressive decrease of measured zinc concentrations in EU waters, the RRS further explicitly requested the commission and the member states to carry out further measurements of zinc concentrations in EU waters in order to be able to update the risk analysis of the RA, (which was based on data from before the year 2000), and to consider the outcome of that analysis before considering the necessity to prioritise zinc under the WFD.

-the EU RA process resulted in a significant improvement of the RA methodology to be applied for metals. Any further assessment of zinc in water should apply this advanced methodology, e.g. by incorporating bioavailability, as explicitly requested in the RA (“In every case the bioavailability correction, which has been used in the present RAR, should be incorporated as an essential part of the process.” - risk assessment zinc, part Environment, overall conclusions).

3Recent monitoring data on zinc in EU waters, and updated risk assessment

In the framework of the revision of the list of priority substances under the WFD, recent monitoring data on zinc, were reported by the member states to the commission (INERIS 2009). For zinc, information was reported by 20 of 27 member states. These data are all from the period after the year 2000, so they are an update on monitoring data for zinc and more relevant than the data in the RA. As such, this recent data gathering, done for the priority list discussion, meets the requirements of the EU RRS on zinc for an update of the monitoring data on zinc.

In the ranking following from the analysis of these extensive recent data, zinc ranks as “medium” concern (INERIS 2009). It is however emphasised that in reaching this conclusion, the data were analysed following a simplified approach, and not according to the advanced risk assessment methodology, as applied in the EU RA. In the analysis below, the updated information on zinc is discussed and a full risk assessment, according to the methodology of the RA, is carried out.

Total zinc concentration in water is measured across the EU. The dataset on updated monitored data for zinc in EU waters mentions a 90P zinc concentration of 32 µg Zn/l. This value is based on 5881 stations in 16 countries, and 118827 data points (INERIS 2009).

Calculation of the risk ratio (PEC/PNEC) for EU waters.

Based on the general “EU-wide” 90P total concentration, and applying the methodology as set out in the EU RA, the following can be calculated (table 1):

a) Correction for natural background:

the PNEC used in the RA is an added value, so has to be added to the background zinc concentration. According to the zinc RA, the natural background must be subtracted from the monitored PEC value. The average zinc background in the EU waters is set at 12 µg/l, with a lower estimate of 3 µg/l (RA, EC 2008). So, the PEC add becomes: 32-12 = 20 µg Zn/l (average BG estimation), and 32-3 = 29 µg/l (lower BG estimation).

b) Dissolved concentrations:

the PNEC is expressed on a dissolved concentration basis. PEC and PNEC must be expressed on the same basis, so, the dissolved fraction of the PEC must be calculated from the total fraction. According to general RA methodology, the dissolved concentration can be calculated from the total, using the partition coefficient between zinc in water and suspended matter:

[Me]diss = [Me]total / 1+(Kp*Cs), where

-Kp: water-suspended matter partition coefficient for metal X (for zinc: 110000 l/kg (EU RA))

-Cs = suspended matter concentration (for this general analysis, the TGD default value is used: 15 mg/l)

Calculated for zinc: [Zn]diss = [Zn]total / 1 + (110000 l/kg * 0.000015g/l) = [Zn]total / 2.7

The dissolved zinc concentration, to be compared with the PNEC is thus: 20/2.7=7.4 µg/l (average BG correction), and 29/2.7=10.7µg Zn/l (lower BG correction).

c) Inclusion of bioavailability:

Finally, a correction for bioavailability of zinc in the natural waters needs to be made (ECB 2008). Lacking evidence on the physicochemical conditions of the waters in the updated monitoring database, several lines of evidence on EU water conditions can be used for setting an overall, representative but at the same time conservative value for zinc bioavailability:

  • Using 50P values reported for dissolved organic carbon (DOC), pH and hardness in the EU, a typical bioavailability of zinc of 0.44 can be calculated (FOREGS 2006).
  • In the RA, physicochemical conditions were reported for several EU waters. They allow to calculate typical bioavailability factors for zinc of 0.4-0.5.
  • In a detailed UK report (UK EA 2005), a general bioavailability factor of 0.6 was applied.
  • The value of 0.6 is applied in the present analysis as an average, but conservative estimation of bioavailability of zinc in the EU waters.

The bioavailable fraction of zinc, to be compared with the PNEC according to the RA, is thus: 7.4µg/l*0.6= 4.4µg/l, and 10.7*0.6= 6.4µg/l, resp.

d) The generic Risk ratios (PEC/PNEC) calculated according to the RA, are:

4.4µg/l/7.8µg/l = 0.6 , and 6.4µg/l/7.8µg/l = 0.8, resp.

In conclusion, when the methodology and reference values of the EU RA are applied, the updated monitored information on zinc levels in water demonstrates that there is no general risk related to zinc in EU waters (see table 1 below).

Table 1: Assessment of the recent monitored data on zinc, reported by 20 of 27 EU member states, according to the methodology as applied in the EU RA on Zinc (ECB 2008).

Zn RA methodology (ECB, 2008)
Measured 90 P [Zn] total (µg/l)
(20/27 countries ; “PEC2”)* / 32
PEC added (µg/L)
(correction for natural background**) / 20 (29)**
PEC dissolved, calculated from total [Me]diss = [Me]total / 1+(Kp*Cs) / 7.4 (10.7)
PEC added, bioavailable (µg/L)
(Bioavailability correction; typical case EU waters: 0.6***) / 4.4 (6.4)
PNECadded (µg/L) / 7.8 µg/l (includes safety factor 2)
PEC/PNEC (“Risk Ratio”) / 0.6 (0.8)

*due to significant uncertainties about the quality of the bulk of the dissolved data, only the PEC total is considered to reflect the general water quality across the EU. Since all data need to be considered for making the assessment of water quality, including data below detection limit, the PEC2 (INERIS 2009) is used in the further analysis.

**equilibrium partitioning coefficient (2.7) and regional background taken from the RA (ECB 2008). Two values are given: average background according to RA, and (between

brackets) the calculation done with the lower estimate of the natural background in EU waters (RA)

***Conservative estimation of the average bioavailability of zinc in EU waters, based on data reported in the EU RA.

It is noted that this result integrates significant level of conservatism, e.g. an additional safety factor on the PNEC, and possible inclusion of point source monitoring. The calculations have been done using typical reference values, used in the RA, because the lack of detail on the current monitored detail does not allow for a more detailed analysis. However, the basic rules of conservatism of RA (90th percentile exposure compared with conservative PNEC) are applied here.

The update of the RA monitoring data that was requested by the EU risk reduction strategy before considering the possible inclusion of zinc into the next revision of the priority list, results in a conclusion of no risk for EU waters in general.

This conclusion is different from the one in the RA which was based on older and more limited data. Following the explicit request of the RRS for this update, the outcome of the RA needs thus be re-considered in the light of the more recent analysis.

Dissolved zinc concentrations in EU waters

A number of countries also reported dissolved zinc concentrations. Surprisingly, the 90P of the dissolved zinc concentrations is higher than the 90P of the total concentrations. Yet, the dissolved fraction is only part of the total, and thus should be lower, logically. This anomaly can be explained by a number of reasons:

  1. The country-specific analysis (see section 4 below) indicates that 85% of the data in the dissolved dataset were reported by only one country (Spain). A basic methodological problem was identified with this Spanish dataset: the samples were at the spot directly stabilised with HNO3 to pH 1-2, before sending them out for analysis. As such, zinc was extracted prior to analysis, and the results cannot be considered as “dissolved” zinc concentration. The bulk of the “dissolved” dataset is thus not reflecting dissolved concentrations. For this reason, the calculated 90P concentration (INERIS 2009) cannot be used[1].
  2. It is well documented that significant contamination of the sample can occur when the sample is filtered in order to separate the dissolved from the total fraction. As a result of this manipulation, dissolved concentrations higher than total have been measured (STOWA 2008). In the zinc data set, there are 192 051 analyses, of which 118 825 are on whole water and 62 082 on dissolved water (of which 47818 were from Spain). In most cases however, the analyses are conducted on different stations and separate samples. Only 74 stations have 1525 samples with analyses on dissolved and whole water at the same date, of which 20 stations corresponding to 36 samples have dissolved concentration above whole water concentration. Although this limited comparison shows that contamination of the samples is possible, the paired data are too limited to conclude on the importance of this effect.
  3. The dissolved and total zinc concentration data were in most cases not monitored at the same stations nor even in the same countries/regions. The datasets on dissolved and on total are thus covering different areas. This may explain why the dissolved 90P is higher than the total 90P. Until there is more detailed information on the origin of the data, this remains unsolved. However, the fundamental uncertainty related to the relevancy of the dissolved concentrations for the current exercise remains. In this respect, it should be recognised that elevated zinc background due to local geological conditions can also be a reason for higher monitored values.

In conclusion, there is significant uncertainty regarding the relevancy of the measured dissolved zinc data for assessing the general water quality in the EU. Given that the total data are measured across the EU, that samples for total concentration analysis are not further manipulated, minimising the chance for contamination and other artefacts, and that there is fundamental uncertainty related to the quality and relevancy of the dissolved monitored data, the total measured zinc concentrations are considered more reliable and more relevant for the ongoing exercise of prioritisation.

4Analysis of country data

For being compliant with the EU risk reduction strategy, and, notably, for answering the question if there is still a “significant risk” related to zinc in the EU (cfr WFD), a more detailed analysis of the monitored data, available by country, was made.

This country-level analysis has the following objectives:

  • Update country information on monitored zinc levels in water as compared to the data reported in the EU RA (consider post -2000 data against monitored data from before the year 2000 in the RA)
  • Assess the currently observed risk level based on the recent monitored data using the established methodology from the EU RA
  • If risk observed, identify the sources of zinc that are significantly influencing zinc levels in these waters

This analysis will allow:

  1. To check if there is significant EU wide-spread risk related to zinc in EU waters
  2. To identify significant sources of zinc, leading to exceedance of PNEC, if any

4.1. Total zinc concentrations measured in waters of EU member states

Data on total zinc concentration were reported by 16 member states. The country-PEC is, according to the methodology followed in the prioritisation process, expressed as the 90P of the arithmetic means by sampling station. The PECs are given by country in table 2. Values in black are obtained from calculating the 90P from > 30 sampling stations, and are considered reliable. Values indicated in red are calculated from less than 30 stations and are therefore statistically not reliable (EU Commission, 2010); they are given as supporting evidence, only.

Risk levels were calculated by country according to the principles, applied in the EU RA:

  1. -the RA PNEC of 7.8µg/l was applied (this PNEC includes an additional assessment factor of 2 on the measured ecotoxicity level)
  2. -PEC values were corrected for background applying the average and worst case background levels for zinc as applied in the EU RA (12 and 3 µg/l, respectively), to get the “PEC add”
  3. -“PEC add” values were converted to dissolved concentration (to be compared with the PNEC) by applying the equilibrium partitioning approach (cfr section 3). A conservative concentration of suspended matter (15mg/l) was applied in this, according to the EU RA.

Finally, a general correction of 60% bioavailability was applied, according to information on physicochemical conditions of EU waters, from the RA and other sources (see section 3). It was not possible to make a more precise correction for this, since the necessary data were lacking. A similar factor was applied by e.g. the UK in its analysis of UK waters (EA UK 2005).