As the only continent without a native human population, Antarctica has experienced less pressure from human activities than other continents. However, the southern continent, and its surrounding seas and islands, have not escaped the effects of these activities. Pollution Despite the large distances separating Antarctica from the rest of the world, pollution is present in Antarctica, whether from legacy or contemporary station operations, or transported from other continents by air or water. Pollution from stations Emissions from exhausts of machinery, oil spills, sewage outfalls and abandoned tip sites are all primary sources of hydrocarbon and heavy metal contamination in Antarctica (Stark et al. 2016, Raymond et al. 2017, Chu et al. 2019). The Australian Antarctic Division’s Environmental Management System supports a reduction in pollution from stations during the planning, operational and continual improvement stages. Recent incident and hazard reporting has resulted in actions to reduce emissions from incineration of waste, and has improved fuel spill response and spill vigilance by expeditioners. Waste Contaminated waste disposal is a product of past practices of Antarctic expeditions. Before the Protocol on Environmental Protection to the Antarctic Treaty (the Madrid Protocol) was signed in 1991, rubbish was dumped at various locations near the stations, or was disposed of by leaving it on the sea ice until it broke out, which resulted in waste and contaminants entering the terrestrial and marine environments. Some contaminants are present in quantities known to be hazardous to the environment. Although frozen for much of the year, these contaminants, either dissolved in water or attached to sediment, can be mobilised during the summer months when there is increased water flow through contaminated areas from snowmelt. The Environmental Aspects and Impacts Register identifies waste-management impacts and associated mitigation measures required to minimise waste at the activity level. Fuel Each of Australia’s permanent stations has an oil spill contingency plan. This is a requirement of Article 15 of the Protocol on Environmental Protection to the Antarctic Treaty. Any ship owned or chartered by the Australian Antarctic Program also must have a current contingency plan. Depending on their role, any expeditioners participating in major fuel transfer receive basic or specialist training. However, accidents happen. The largest ongoing risk and source of new pollution in Antarctica is associated with storing and handling bulk volumes of fuel. As part of the Australian operations, large quantities of Special Antarctic Blend fuel (more than 1 million litres (L) per station per year) are transferred from a ship, and stored and handled at the stations. The climate in Antarctica presents significant challenges for infrastructure and operations. There is always the risk of spills when transporting, handling or storing fuel. Land-based fuel spills, some as large as 15,000 L, have occurred in the past, because of mechanical failures or human error during transfer from ship to shore or transfer between storage tanks and powerhouses. Fuel spills occurred, mainly caused by equipment failure but also by human error. The effect of one oil spill of 4,000 L was rated as high, and the effect of another of just over 1,000 L as medium (DEE 2019). Half of all recorded spills were 10 L or less, and 85% were less than 200 L, the official reporting level for spills of the Committee of Managers of National Antarctic Programs (COMNAP) (COMNAP 2008). At times, fuel storage tanks, valves and piping have leaked during winter, and the leaks have gone unnoticed until the summer melt revealed that these storages had drained their contents. Today, all tanks are bunded (surrounded by a secondary containment that minimises or eliminates any fuel leakage from fuel storage areas). Hence, the environmental damage is reduced or avoided altogether. However, not all fuel infrastructure (e.g. fuel transfer pipework, flanges, pipe joins) has secondary containment. At Davis and Casey stations, the Australian Antarctic Division (AAD) has successfully remediated soils contaminated from several fuel spill events at the bases, and used remediated soils in local building projects (McWatters et al. 2016b). Recently, several tip sites and old fuel spill sites have been assessed and remediated. At the time of writing, the most significant fuel spill remediation underway is of contaminated soil and water at 4 spill sites at Casey Station; 2 of these incidents occurred in 2015 and 2018 when a connection in the fuel transport infrastructure leaked and contaminated the site. Another potential source of fuel contamination derives from empty fuel drums. If left in situ, they will eventually rust, and residual fuel will leak into the environment. In the 2014–15 season, the AAD removed 2,600 crushed steel drums (weighing nearly 50 t) from Davis Station for recycling in Australia (Greenslade et al. 2008). These incidents have been the subject of root-cause investigations, and comprehensive assessment and remediation planning have been conducted to identify the best course of action in containing and remediating the site. A major theme of Australia’s Antarctic Science Program is scientific and engineering research to understanding, assess, remediate and monitor human impacts. Further strategic planning for assessment and clean-up of contaminated sites within the Australian Antarctic Territory is a key deliverable of the 2016 Australian Antarctic Strategy and 20 Year Action Plan (Australian Antarctic Programme 2016). Building materials Some station buildings contain asbestos and are listed in the AAD’s asbestos register. The AAD is addressing this hazard and is progressively removing asbestos from its buildings. For example, the former living quarters at Davis Station contained a significant quantity of asbestos. This was removed and returned to Australia in 2015. Other areas, such as Heard Island, present a greater challenge. The decay of buildings and structures, and the extent of asbestos debris on the island were assessed in 2012. However, there has not yet been an opportunity to undertake any clean-up activity at the site of the former Australian National Antarctic Research Expeditions station at Atlas Cove on Heard Island. The AAD provides warnings and advice to government and nongovernment operators intending to visit the site, as part of the permitting process provided for in the Heard Island and McDonald Islands Marine Reserve management plan, and the Environment Protection and Management Ordinance 1987 to the Heard Island and McDonald Islands Act 1953. Pollution from global sources Pollution and toxins can arrive in Antarctica from all over the world. Plastics can travel on ocean currents. Winds can transport volatile substances into distant areas, and pollutants with a long atmospheric residence time can disperse on a global scale (GESAMP 2001). Plastics Plastic pollution due to unsustainable use and disposal of plastics is a serious threat to the environment and human health. This is an area of international research through the SCAR Action Group on Plastics in Polar Environments. Plastics increasingly contribute to environmental pollution both on land and at sea, and endanger wildlife (Waller et al. 2017). Although the Southern Ocean is still comparatively unpolluted, some subantarctic regions – particularly in the Indian Ocean – are becoming increasingly exposed to plastic pollution (Perold et al. 2020). Entanglement in plastics, such as ropes, nets and monofilaments used in commercial fishing operations, threatens at least 243 species. Entanglement often results in death and may be responsible for most plastic-related deaths. For example, young Antarctic fur seals (Arctocephalus gazella) can become caught in plastic materials; as the animals grow, the plastic tightens and cuts into their bodies (Pemberton et al. 1992). As plastics persist for years in the environment and do not decompose, they can kill repeatedly once the carcases of entangled animals have decomposed (Mattlin & Cawthorn 1986). There are concerns about an increase in plastic waste at high latitudes, particularly with regard to seabirds that frequently ingest marine plastic debris (Wilcox et al. 2015, Kühn et al. 2021). Plastics are also ingested by marine predators, either directly when they forage (primary ingestion) or indirectly when they receive it from contaminated prey species (secondary ingestion). A long-term study at Marion Island, in the southern Indian Ocean, documented a decrease in fisheries-related plastics as fishing activities in the region decreased after 1999, but noted a near-simultaneous increase in other litter. Matter regurgitated by wandering and grey-headed albatrosses, and giant petrels contained food packing, plastic bags and rubber gloves (Perold et al. 2020). Near Antarctic stations, plastic ingestion has been noted, for example, in 9% of brown skuas (Stercocarius antarcticus lonnbergi) at Esperanza Bay, Antarctic Peninsula (Ibañez et al. 2020). At Haswell Island, East Antarctica, a 23 cm piece of synthetic rope (possibly a snood from a fishing line) was discovered in the stomach of an emperor penguin chick. The rope probably did not cause the death of this chick (Golubev 2020). However, among petrels, up to 63% of deaths were due to ingestion of plastics (Rochman et al. 2016). Small petrels are particularly at risk of dying when plastics become lodged in their digestive systems, while large petrels and albatrosses may pass on the contaminants to their chicks (Petry & Benemann 2017). In addition to macroplastics, microplastics (less than 5 mm) are of concern as they spread through the food web. For example, at Macquarie Island, microplastics were isolated from fur seal scats, the result of secondary ingestion of big-eye lantern fish (Electrona subaspera) (van den Hoff et al. 2018). As filter feeders, baleen whales also ingest microplastics directly (Besseling et al. 2015). Toxins Heavy metals occur naturally in the environment and can be transported via sea-spray, windblown dust and volcanism (Dick 1991). Industrial and agricultural contaminants have reached Antarctica through global circulation (Chu et al. 2019). Organochlorine pesticides such as hexachlorocyclohexanes (HCHs) and other persistent organic pollutants (POPs) travel large distances through the atmosphere (Corsolini et al. 2002). Some chemicals can reach the polar regions through a process known as ‘global distillation’: volatile chemicals evaporate in the warmer places where they are used and condense in colder places to which they are transported (Mackay & Wania 1995, Yamashita et al. 2018, Bertinetti et al. 2020). Airborne pollutants can be deposited into the ocean and land environments, where they may enter the food web. For example, dichlorodiphenyltrichloroethane (DDT; a synthetic pesticide once widely used) and its derivatives bind to particles in water and to organic matter where they remain for many years. Since POPs accumulate in phytoplankton, they enter the food web at its very base (Chiuchiolo et al. 2004). Plankton (krill, copepods and fish larvae) ingest the pollutants, which accumulate in their fatty tissue. Since toxins are not digested, seabirds and marine mammals acquire them through their diet, and the toxins are concentrated through the food web (a process called bioaccumulation) (Corsolini et al. 2002). As part of their adaptation to life in the extreme cold, Antarctic organisms often have high levels of fats, which can result in the bioaccumulation of fat-soluble toxins (Corsolini et al. 2017). For example, POPs have been isolated from the blubber of fin whales (Taniguchi et al. 2019). Biopsied tissues taken from fin whales feeding near the Antarctic Peninsula contained hexachlorobenzene (HCB; a fungicide), DDT and derivatives, HCHs and polybrominated diphenyl ethers (PBDEs). DDT levels were 15–380 times higher than in specimens collected in the Northern Hemisphere. PBDE levels were similar to samples from the Northern Hemisphere, whereas HCH content was lower (Taniguchi et al. 2019). An issue of concern is that fat-soluble (lipophilic) pollutants accumulate in the tissues of female whales. Many species spend the austral summer in the Southern Ocean where they feed extensively before they head north to their breeding grounds. During their migration and breeding time, the whales often undergo periods of fast. Toxins stored in the mother’s fat become mobilised and can also be transferred to the embryo and calf. The impacts of this on the whales’ immune function, for example, need urgent attention (Nash 2018). As early as the 1960s, traces of DDT were detected in the fat tissue of Adélie penguins (George & Frear 1966). In 1978, DDT and its derivatives were found in tissues and eggs of 3 species of brush-tailed penguins (Pygoscelis spp.) on the Antarctic Peninsula (Łukowski 1983). The Stockholm Convention on Persistent Organic Pollutants banned the use of this pesticide for general agricultural use in the Northern Hemisphere in the 1970s, and worldwide in 2001. Some countries still produce and use DDT to fight malaria; in 2014, some 3,772 t were produced globally – a 30% decrease since 2001 (van den Berg et al. 2017). In 2010, DDT still occurred in the feathers of Adélie and gentoo penguins (Metchava et al. 2017). POPs, including DDT, have also been detected in 5 lakes in the Larsemann Hills, East Antarctica (Bhardwaj et al. 2019), and DDT, HCHs, HCB and polychlorinated biphenyls (PCBs) were found in the soils and some lichen on the coast of East Antarctica (Negoita et al. 2003). DDT was also detected in the muscle tissue of Antarctic toothfish in the Ross Sea at relatively high levels (20.1 ± 6.70 nanograms per gram wet weight). These fish are relatively slow-growing, long-lived predators (living to around 50 years). Thus, toxins can potentially accumulate in their tissues for decades. Weddell seals, predators of Antarctic toothfish, also had elevated levels of DDT in their livers (Corsolini et al. 2017). A number of new POPs have been reported from Antarctica, including polychlorinated naphthalenes (PCNs), hexabromocyclododecanes (HBCDs), and polychlorinated compounds such as Dechlorane Plus (DP) and related compounds (Kim et al. 2021). It is currently unknown how far they are spread; PCNs have so far only been reported from the Ross Sea (Grotti et al. 2016). However, this is due to a paucity of studies. Dechlorane Plus is a flame retardant for plastics that is added, for example, to the coating of electrical wire and cables, used in TV connectors, and is also used in computer screens (Persistent Organic Pollutants Review Committee 2020). DP appears to cause metabolic and developmental disorders in animals (Kim et al. 2021) and is currently under consideration for listing under the Stockholm Convention. Brominated flame retardants were recently detected in the soil of Adélie penguin colonies in East Antarctica (Lewis et al. 2020). In various regions of Antarctica, mercury, lead, cadmium and other metals have been isolated from many different organisms, such as penguins (Jerez et al. 2013, Pacyna et al. 2019), flying seabirds (Tartu et al. 2015, Becker et al. 2016, Souza et al. 2020), various marine invertebrates (Webb et al. 2020), lichens and mosses(Zvěřina et al. 2014), and yeasts (Fernández et al. 2017a). Phenol-degrading yeasts are tolerant of heavy metals and may find a use in the treatment of wastewater in cold environments (Fernández et al. 2017a). The 4 penguin species at Macquarie Island all had traces of mercury in their feathers. The levels in 2002–03 were significantly different in all species from historical values (1937–76). Although mercury levels had decreased in king and royal penguins, they had increased in gentoo and rockhopper penguins. Variability in diet and foraging strategies may explain interspecific differences, but the reasons for the different trends are still unclear (Gilmour et al. 2019). Metal contamination can be a problem in the nearshore environments of stations. Various metals, such as chromium, iron, nickel and zinc, are essential for the maintenance of healthy function. However, when these so-called trace elements surpass a certain threshold, they can become toxic. In marine algae, for example, metal uptake from the environment is highly regulated. However, when different metals occur together at elevated levels, they may affect an organism differently from when they occur by themselves. For example, 2 Antarctic marine microalgae – Phaeocystis antarctica and Cryothecomonas armigera – were exposed experimentally to cadmium, copper, nickel, lead and zinc to examine toxicities of the metal mixture compared with a single metal. Both algae accumulated metals in their cells; copper appeared to drive toxicity, whereas zinc appeared to provide some protection from toxicity of the other metals. Depending on the mixture and relative concentration of the various metals, there is a risk of bioaccumulation of metals and potentially toxicity in the Southern Ocean food web at the level of microalgae and grazing plankton (Koppel et al. 2019). Large-scale processes underlie the presence of POPs in Antarctica. The best-studied component is probably DDT and its derivatives. Penguin samples collected over the past five decades show that the concentration of dichlorodiphenyldicholorethylen (DDE), a derivative of DDT, rose from the 1960s, peaked around 1985 and has steadily declined since (Ellis et al. 2018). The decrease of POPs in the Southern Ocean may indicate that these compounds have left the pelagic environment and have entered the benthic realm. As part of the biological carbon pump, POPs bound to organic matter, such as moulted exoskeletons of krill or faeces expelled by vertebrates while at sea, sink to the ocean floor and accumulate there (Ellis et al. 2018). Antarctica provides an important site for monitoring global background levels of known contaminants controlled by the Stockholm Convention (SSC 2020), and marine sediments and benthic communities may need to be examined to assess levels of POPs and other pollutants.