Organic pollutants in the marine environment
The downside of consumptionChemical-based products are found in plastic casing for computers, in athletic-hall flooring, in rubber soles for jogging shoes – the applications are endless. In consequence, a very wide range of chemicals is used in industry today. According to the Organisation for Economic Co-operation and Development (OECD), approximately 100,000 different chemical substances are currently on the market worldwide. In Europe alone, approximately 10,000 chemicals are produced and marketed annually in amounts of greater than 10 tonnes. It is estimated that between 1 and 3 per cent of these chemicals are problematical. These environmentally relevant pollutants include heavy metals such as lead and mercury, which are released into the environment by the burning of oil, mining activities, and industrial emissions and effluents. Persistent organic pollutants, known as POPs, are another problematical substance category.
- 4.6 > During the phocine distemper virus (PDV) epidemics in 1988 and 2002, thousands of dead seals were washed up on German beaches and had to be collected and destroyed.
Poisonous and persistent – POPsThe Stockholm Convention on Persistent Organic Pollutants adopted in 2001 deals with persistent organic pollutants (POPs), i.e. substances that possess toxic properties and resist degradation. They include pesticides such as DDT and lindane, industrial chemicals such as polychlorinated biphenyls (PCBs), and substances such as dioxins, which are the unwanted by-products of manufacturing and combustion processes. As these substances are highly stable and therefore non-degradable to a large extent, they can be transported over long distances and accumulate in the environment.
POPs cause problems because they are stored in the fatty tissue or organs of animals, where they can have toxic effects. For example, they can disrupt the endocrine system, cause cancer or genetic defects, and weaken the immune system.
Various effects of POPs on marine mammals have been investigated. Studies of Baltic ringed seals (Phoca hispida) and grey seals (Halichoerus grypus) found uterine occlusions, stenoses and tumours, resulting in reduced reproductive ability. Other observed effects included colonic ulcers, as well as reduced bone density, which led to changes in the skeletal system. In seals and porpoises, researchers found indications that POPs depress the immune and endocrine systems. A further topic of discussion in this context is whether these pollutants and the weakening of the immune system affect the spread of epidemics, such as the disease that killed thousands of seals in the North Sea in 1988 and again in 2002 – probably an epidemic of the phocine distemper virus. Humans mainly ingest POPs from food and drinking water, but also from the air (mainly by breathing in dust particles) and through the skin (through direct contact with the chemicals). The highest concentrations of POPs are generally found in marine mammals and humans, both of which are at the top of the food chain.
- 4.7 > Bioaccumulation of toxins in the marine food chain has long been recognized as a problem. The process illustrated here relates to polychlorinated biphenyls (PCBs), a typical environ-mental toxin.
Polyfluorinated compounds: a fresh cause for concernBesides the “classic” POPs, mentioned above, new types of persistent toxic compounds of non-natural origin were identified in the environment at the end of the 1990s, which could not be detected before as the appropriate technology and analytical methods had not yet been developed. These include polyfluorinated compounds (PFCs), which have been used in a wide variety of every-day applications for more than 50 years. PFCs are mainly used as fluoropolymers in the textile industry, for example, in the manufacture of breathable membranes for outdoor clothing, and in the paper industry in the production of water-, stain- and grease-proof paper (e.g. fast-food packaging). They are also used for surface treatment of furniture, carpets and clothing textiles and in non-stick coatings for cookware (such as Teflon frying pans).
It is believed that a total of six manufacturers have produced around 4500 tonnes of PFCs every year over the past decade: a relatively small amount compared with other chemicals. This group of substances is significant nonetheless, due to its environmentally relevant properties, as some PFCs are highly bio-accumulative in organisms.
At present, more than 350 different PFCs are known to exist. The best-known is perfluorooctanesulfonic acid, more commonly known as PFOS. Based on animal experiments with PFOS, researchers conclude that repeated exposure can have an extremely adverse effect on human health; among other possible effects, it may cause damage to the liver. PFOS may also be carcinogenic, and it is also thought to impair the development of progeny. PFOS therefore recently became the first PFC to be listed as a persistent organic compound (POP) under the Stockholm Convention, which means that it is now on the list of particularly hazardous chemicals for which a worldwide ban is to be imposed.
Occurrence of polyfluorinated compoundsPolyfluorinated compounds (PFCs) have been industrially manufactured for around half a century, but it has only recently been possible to detect their presence in the environment due to new chemical and analytical techniques. Natural origins of these chemicals are not known to exist, and yet today PFCs can be detected in water, soil, air and living organisms worldwide – including humans. High levels of PFCs have been found in numerous foods as well as in human blood and breast milk.
The distribution of PFOS in the environment is particularly well-researched. High concentrations of these substances have been detected in fish, seals and sea birds worldwide and, above all, in Arctic polar bears, which are at the top of the food chain. Researchers from Canada and Denmark have reported a sharp rise in PFOS concentrations in liver samples taken from polar bears in Canada, Alaska and Greenland in recent decades. Compared to other environmentally relevant POPs, such as polychlorinated biphenyls, PFCs are found in much higher concentrations. In Swedish studies of human blood from 1994 to 2000, the mean PFC concentration was 20 to 50 times higher than the concentration of the polychlorinated biphenyls and about 300 to 450 times higher than that of hexachlorobenzene, two “classic” organic pollutants that have been recognised as hazardous for decades.
- 4.8 > PFOS concentrations in the livers of East Greenland polar bears have increased significantly in recent years. The measurements were obtained from deep-frozen liver samples.
Transport of PFCsThe detection of PFCs and especially PFOS in marine mammals such as Arctic seals and polar bears, and even in the blood of the Arctic’s human inhabitants, the Inuit, raises the question of transportation: How did these substances end up in the sea and even in the Arctic? There are numerous different sources of PFCs. They are released, for example, during the use of the everyday consumer durables mentioned above – from carpeting, outdoor clothing, cookware and fast-food packaging. However, in Germany, relatively large concentrations of PFCs also enter the rivers from municipal and industrial wastewater treatment plants, which cannot capture these substances. The rivers then wash these substances into the North Sea. From here, they are carried by the main North Sea and Atlantic Ocean currents to the Arctic, where they are ingested by microorganisms in the water and thus enter the food chain, bioaccumulating in larger organisms and finally in the organs of polar bears and humans.
PFCs are also transported long distances through the atmosphere by the movement of air masses. Compounds such as PFOS are not volatile, but volatile precursor compounds escape into the atmosphere during the manufacturing process. Physical and chemical processes that take place in the atmosphere then convert these chemical precursors into stable end products such as PFOS. These are removed from the air by precipitation and enter the seawater in soluble form or bound to dust particles, or are deposited on land or ice surfaces. PFCs can thus travel great distances and can be detected in the environment a long way from their place of origin or use.
- 4.9 > PFCs can travel great distances in water or air. Through a direct pathway, they enter the rivers in wastewater and are carried down to the sea. They can also be transported indirectly through the atmosphere. For example, volatile PFOS precursors are released into the atmosphere, where they are converted into PFOS, which is then deposited back on the Earth’s surface at the place of origin or elsewhere in rainfall or in dust particles.
Protection from new pollutantsToday PFCs are distributed all over the world. They are found in water, in the air, in living organisms and even in our own bodies. They are likely to persist for generations. This group of substances clearly shows that it is impossible to predict all the environmental impacts, or the delayed effects, of new chemical substances. In the future too, it is likely that some substances that were initially regarded as harmless, but whose undesirable effects can only be discerned after some time has elapsed, will be detected in the marine environment. Nowadays, however, intensive efforts are being made to limit the further global spread of pollutants. For example, risk assessments are carried out before chemicals are licensed for use, in order to determine to what extent they could constitute a hazard. There are also various voluntary renunciation schemes for producers, as well as relevant legislation. In other words, a start has been made.