Micropollutants in Antarctic waters

Antarctica is one of the last remaining places on Earth relatively untouched by humans. Most scientific research stations are located adjacent to the coast, discharging wastewater and sewage containing a wide range of pollutants into the sea¹. Under Annex III of the Protocol on Environmental Protection to the Antarctic Treaty (Article 5), liquid sewage needs to only be macerated before being discharged from stations with more than 30 persons. As a result, the wastewaters from 37% of permanent research stations and 69% of summer stations lack any kind of treatment. Whilst most Parties now remove all solid human waste from field party sites it is permissible under the Protocol Annex III to dispose of raw human waste and grey water directly into the ocean via tidal cracks in the sea ice. Under Annex IV of the Protocol on Marine Pollution ships are also allowed to release macerated food waste and sewage into the ocean, when at least 12 nautical miles from the coast or ice shelf.

Pharmaceuticals and Personal Care Products (PPCP) are found in domestic and industrial wastewater discharged into the environment around the world and have been classified as micropollutants². Some of the chemicals in PPCPs appear to be persistent in the environment³, and many conventional sewage treatment methods cannot completely remove some of them from wastewater⁴. Environmental impacts are now emerging for which these chemicals were not previously tested^{4, 5}, which include biological effects such as disruption of the endocrine system (hormones) of vertebrates and invertebrates. Hormones play a key role in the developmental and reproductive activities of animals, and these disruptive compounds in freshwater environments have been shown to have significant environmental impacts, such as changing the gender of fish⁵. There has been little research on these in the marine ecosystems anywhere.

A initial study in 2009 showed that micropollutants were present in the sewage effluents of Scott Base and McMurdo Station, as well as in the nearby coastal environment. Based on these data in a follow-up study in 2012 the distribution of PPCPs over a wider area in McMurdo Sound was investigated⁶.

The analysed effluents from Scott Base and McMurdo Station were identified as the main source for a wide range of PPCPs, while the dumping of untreated human waste through the sea ice, including waste from the sea ice airport (a practice that has now ceased) has been identified as a possible minor source [6]. Seawater samples and benthic organisms taken from Pegasus Bay (Ross Island, Antarctica) showed a wide distribution of PPCPs, being detected up to 25 km up-current from the research stations. Attention was focussed on several classes of compounds:  UV sunscreens, anti-microbial agents, surfactants and steroid hormones (Table 1)⁶.

Table 1. Chemical compounds from PPCP degradation and hormones detected in Antarctica

The most commonly detected micropollutants in effluent and seawater were OP, 4-MBC, BP-3, BP-1, triclosan, methyl triclosan, BPA, E1, and Cstanol (Table 1) used predominantly in personal care products. The effluent concentrations of these compounds were comparable to previously reported international data. For comparison micropollutant concentrations in New Zealand effluents ranged from low to mid ng L^-1 levels, while Antarctic effluent concentrations ranged from low ng L^-1 to low μg L^-1 levels. The maximum effluent concentrations of OP, 4-MBC, BP-1, E1, and EE2 detected during the 2012/2013 season were higher than those previously reported internationally⁶.

Although major release from Antarctic sewage systems is largely confined to the summer period while personnel numbers are high, their potential persistence in the environment means an opportunity for biological uptake of these pollutants by marine organisms exists throughout the year, including the winter months when effluent discharges are low. Antarctic clams (Laternula elliptica), sea urchins (Sterichinus neumayeri), and fish (Trematomus bernachii) were shown to bioaccumulate PPCPs (mParaben, pParaben, BP-3, E2, EE2, OP, Cstanol), and evidence from other marine environments show that sediments are also a likely sink  of PPCPs⁶. However, most data for bioaccumulation of these types of compounds still comes from Northern Hemisphere research. Whilst generally the tissue concentrations in Antarctica of OP, BP-3, and EE2 are comparable to previously reported international data⁶, some tissue concentrations of BP-3 exceeded previously reported international data four-fold⁶. The samples from the Ross Sea are the first to show the bioaccumulation of mParaben, pParaben, and E2 in environmental samples at comparable levels to the Northern Hemisphere, and that the biological impacts will therefore likely be of an equal magnitude, if not more. UV filters in sunscreen are known to exhibit estrogenic activity², OP can cause endocrine disrupting effects in marine and freshwater species⁷, and triclosan is toxic to algae, micro-organisms, and fish larvae⁸. Steroid hormone residues, triclosan and BPA are biologically effective at very low environmental concentrations^{8, 9}.

The same range of micropollutants were detected in the sewage effluents, seawater, and biota from the comparative New Zealand study⁶. However, the maximum concentrations of micropollutants in sewage effluents were higher in the Antarctic than in New Zealand. Month to month concentration fluctuations were also greater in Antarctica, and dispersal up to 25 km from Scott Base and McMurdo Station was an unexpected finding⁶.

Recent studies at Terra Nova Bay have detected for the first time a range of fragrances from PPCPs in sea water including Ambrofix, amyl salicylate, benzyl salicylate, hexyl salicylate, Lemonile and Okoumal, reaching a combined concentration of up to 100 ngL^-1. Sewage treatment did not remove the fragrances and concentrations in nearby Tethys Bay increased during the seasonal melt of the sea ice and its snow cover¹⁰.

Most recent work surveying micropollutants in Antarctica has identified 16 pharmaceutical products including analgesics and  recreational drugs including caffeine in the Antarctic Peninsula region¹¹. Based on calculated Toxic Unit values analgesics and anti-inflammatories are identified as those most likely to be of concern in Antarctic marine ecosystems but all are present in very low concentrations.

Experience with wastewater plants similar to those in use in Antarctica data show the design to be ineffective in removing these micropollutants¹². While there is some experimental evidence that natural photodegradation by UV in sunlight can help in reducing the concentrations of some compounds¹³ it is clearly not sufficient. Initiatives elsewhere may provide new engineering options for Antarctic sewage treatment which may include UV and other treatments, some of which have been installed in some stations¹⁴.

The bioaccumulation of mParaben and pParaben in the Antarctic biota was unexpected as it is only recently that this has been demonstrated for any marine ecosystems¹⁵ suggesting a wider range of micropollutants may be of environmental concern than previously thought. The maximum aqueous concentrations of detected PPCPs were orders of magnitude lower than those reported to induce biological effects. The more biologically active steroid hormones E1, EE2, and E3 were detected only infrequently at concentrations close to the quantification limits. The potential risk these chemicals pose to Antarctic’s unique marine ecosystem remains unknown⁶.

Antarctic biota have very slow metabolisms and are slow growing¹⁶, leading to longer in vivo exposure periods. At present nothing is known about micropollutant adsorption and its effects if tissue concentrations increase over time. In addition the environmental effects of mixtures of micropollutants are unknown since tests everywhere have mainly been on single compounds and the effects of mixtures remains unstudied¹⁷.

Key research questions for micropollutants worldwide have now been identified¹⁸ and could provide a valuable focus for future Antarctic research in this field.