Tributyltin (TBT)

Tributyltin (TBT) is an organic compound of tin used as a biocide especially in marine antifouling paints. TBT is toxic to marine life and was first known used in the 1960ties. In this study, TBT was analysed in blue mussel at seven stations, dogwhelk at eight stations and common periwinkle at one station. Imposex (VDSI) was investigated in dogwhelk at all eight stations.

Environmental Quality Standards (EQS) for EU-priority substances

When applying the EQS for TBT (150 µg/kg w.w.) in biota (“for fish”) on blue mussel

(< 14.0 µg/kg w.w.), dogwhelk (< 9.8 µg/kg w.w.) and periwinkle (< 1.1 µg/kg w.w.), all TBT-concentrations were below EQS in 2017 (Table 11), as in 2016.

Environmental Quality Standards (EQS) for River Basin Specific Pollutants

When applying the EQS for triphenyltin (TPTIN) (152 µg/kg w.w.) in biota on blue mussel (<2.2 µg/kg w.w.), dogwhelk (<32.0 µg/kg w.w.) and periwinkle (<0.5 µg/kg w.w.), all TPTIN-concentrations were below EQS in 2017, as in 2016 (Table 11).

Blue mussel

Levels exceeding PROREF

Blue mussel at Akershuskaia (st. I301) and Gressholmen (st. 30A) in the Inner Oslofjord exceeded the provisional high reference concentration (PROREF) for TBT by a factor of up to two.

Decrease in PROREF factor since 2016

Blue mussel at Akershuskaia (st. I301) and Gressholmen exceeded PROREF for TBT by a factor up to two in 2017, but exceeded this limit by a factor between two and five in 2016.

Downward trends

For blue mussel, there were both significant downward long- and short-term trends for TBT at Akershuskaia (st. I301) in the Inner Oslofjord, at Odderøya (st. I133) in the Kristiansandfjord and at Espevær (st. 22A) in the Outer Bømlafjord. A significant downward long-term trend was also found at Gressholmen (st. 30A) in the Inner Oslofjord and Færder (st. 36A) in the Outer Oslofjord.

Dogwhelk Levels of TBT

The TBT-levels in dogwhelk were low (<2.3 µg/kg w.w.) at seven stations, except for Risøya at Risør (st. 76G) where the concentration was <9.8 µg/kg w.w. due to matrix effects during analysis.

Downward trends of TBT

There were both significant downward long- and short-term trends for TBT at Færder (st. 36G) in the Outer Oslofjord, Melandsholmen (st. 227G2) in the Mid Karmsundet and at Espevær (st. 22G) in the Outer Bømlafjord. There were significant downward trends at Risøya at Risør (st. 76G), at Lastad in Søgne (st. 131G), at Gåsøya-Ullerøya in Farsund (st. 15G) and at Svolvær airport area (st. 98G) in Lofoten.

Biological effects of TBT (imposex/VDSI) in dogwhelk

The effects of TBT, the imposex parameter VDSI, were zero at all eight stations. For the first time since 1991, all results were below the OSPARs Background Assessment Criteria (BAC=0.3, OSPAR 2009) and the OSPARs Ecotoxicological Assessment Criteria (EAC=2, OSPAR 2013) in 2017.

Decrease in VDSI since 2016

The effect of TBT in dogwhelk was lower at Melandsholmen in the Mid Karmsundet (st. 227G2) in 2017 (VDSI=0) than in 2016 (VDSI=1.9). This was also the case at Brashavn (st. 11G) in the Varangerfjord where VDSI was 0 in 2017, while it was 0.04 in 2016.

Downward trends of VDSI

In dogwhelk, both significant downward long- and short-term trends for VDSI were observed at Færder (st. 36G) in the Outer Oslofjord, at Espevær (st. 22G) in the Outer Bømlafjord and at Svolvær airport area (st. 98G) in Lofoten. Significant downward long-term trends were found at Risøya at Risør (st. 76G), at Lastad in Søgne (st. 131G), at Gåsøya-Ullerøya in Farsund (st. 15G), and at Melandsholmen (st. 227G2) in the Mid Karmsundet.

Common periwinkle Levels of TBT

The TBT-concentration in common periwinkle at Fugløyskjær (st. 71G) in the Outer Langesundfjord was 1.1 µg/kg (w.w.).

Trends of TBT

There was were insufficient data to determine if the trend was significantly downward for TBT at in

95

Other studies

Blue mussel from Langøya in the Holmestrandfjord in 2017 were below EQS for both TBT and TPTIN at all three stations, included Mølen (st. 35A) (Schøyen and Beylich 2018). At Mølen, the

concentration of TBT was 3.8 µg/kg w.w. and the concentration of TPTIN was 0.9 µg/kg w.w. The collection of blue mussel took place during the autumn.

General, large scale trends

In this study, synchronous decreases and significant downward long- and short-term trends in levels of TBT, VDSI and Relative Penis Size Index (RPSI) were found in dogwhelk, and the levels were low (Schøyen et al. 2018a and 2018b, in prep). The decreases in TBT concentrations and imposex parameters coincides with the TBT-bans. Populations of dogwhelk have recovered all along the Norwegian coastline after the introduction of bans on the use of TBT in antifouling paint. Former maximum levels of these markers were detected at coastal sites close to active shipping channels like Færder and Karmsund. In populations close to much ship traffic, the recovery took longer time than at remote stations. In the Karmsund area, a maximum level of 46 % sterile females was measured in 2000, whereas there have not been detected any sterile females at any monitoring station after 2008, the year for the total ban. This recovery has also resulted in low levels of TBT and imposex in dogwhelk all along the Norwegian coast.

The results show that the Norwegian legislation banning application of organotin on ships shorter than 25 meters in 1990 and longer than 25 meters in 2003/2008, has been effective in reducing imposex in dogwhelk populations. The international convention that was initiated by the

International Maritime Organization (IMO) did not only ban application of organotin on ships after 2003 but also stated that organotin after 2008 could not be part of the system for preventing fouling on ships. VDSI in dogwhelk was around level 4 in all dogwhelk stations before the ban in 2003, except for the Varangerfjord where the VDSI had been low (<0.3) in the whole monitoring period. It was a clear decline in VDSI as well as TBT at all stations between 2003 and the total ban in 2008 (Figure 31, Figure 32). In the post-ban period since 2008, the VDSI levels have been below PROREF (3.68) at all stations, and the levels has been close to zero at many of the stations. A typical example of decreasing trends is shown for Færder in Figure 33.

Figure 31. Frequency of recent trends for the concentration of TBT in dogwhelk (n=8) (2008-2017).

No upward trends were detected. Concerns about LOQ prevented some trend analyses.

Trend down (50%)

No trend (33.3%)

Trends for TBT in dog whelk

(n=8)

Figure 32. Frequency of recent trends for VDSI in dogwhelk (n=8) (2008-2017). No upward trends were detected.

Figure 33. Changes in VDSI for dogwhelk from Færder (st. 36G) (1991-2017). The vertical black lines indicate the initial ban of TBT in 2003 and total ban in 2008. The provisional high reference concentration (PROREF) and the factor exceeding PROREF are indicated with horizontal dashed lines (see Figure 5 and Appendix C).

In the post-ban period since 2008, TBT concentrations in dogwhelk have been below PROREF (23.5 µg/kg w.w.) at all stations. Discharges of TBT and TPTIN to water from land-based industries from 1997 to 2017 is shown in Figure 34, but do not adequately reflect loads to the marine environment because it does not include discharges from maritime activities for this period and do not include secondary inputs from organotin contaminated sediments. The values were high in 2003 (487 g TBT and TPTIN/year) and 2009 (504 g TBT and TPTIN/year), and these peaks were related to

Trend down (33.3%)

No trend (55.6%)

Trends for VDSI in dog whelk

(n=8)

97

Figure 34. Annual discharges of TBT and TPTIN to water from land-based industries in the period 1997-2017 (data from www.norskeutslipp.no, 8 June 2018). No data are reported for 1994-1996.

The vertical grey line at 1997 marks when the measurements of TBT started. The MILKYS-measurements of VDSI started in 1991. Note that emissions and discharges from municipal treatment plants, land runoff, transportation and offshore industry are not accounted for in the figure. New calculation methods for data of discharges might lead to changes in calculations of present and previous data.