Student assignment. (requirement for course by Peter Kabai)

HIGH LEVELS OF PCB IN THE NORWEGIAN POPULATION OF POLAR BEARS

By Kristine Bull

Introduction

The level of polychlorinated biphenyls (PCBs) in the Norwegian population of polar bears (Ursus Maritimus) at Svalbard is six timers higher than the American population and three times higher than the Canadian. The Russian population is the only population that has higher levels of PCBs. The high levels are believed to post the most acute threat to the population.

To see a figure about circumplar levels of PCBs in polar bears please click on the below link: http://www.environment.no/templates/themepage____2800.aspx

Polar bears

The polar bears are the largest terrestrial predator on the earth. They live in the circumpolar north and scientist have estimated that there are about 22000-27000 animals today. 15000 of them live in Canada while there are about 2000 polar bears on the Norwegian islands of Svalbard.

What are PCBs?

PCBs are group of synthetic chlorinated hydrocarbons which are not easily degraded. They are not flammable and have isolating qualities which made them very popular substances. They were used in several electric systems and as an additive in paint and plastics. There have been developed 209 different types of PCBs and their toxic properties vary depending on the number of chlorine-atoms and the structure of the molecule. Even though PCBs are illegal today it is estimated that 2000 billion kilograms have been produced and about 1/4^th of it has already been released into the environment.

Spreading of PCBs

PCBs spread both trough air and water and are therefore found almost everywhere even though most of it, 60%, is found in the oceans. The reason that the levels of PCBs are higher in the Norwegian population than in the populations of Northern America might be that PCBs pollutions from other parts of the world are transported to Svalbard by the Gulf Stream. The Gulf Stream originates near Florida (US) and flow north passing Svalbard before it terminates in the Barents Sea. As the figure indicates the PCBs transported by the stream will not effect the Canadian and American populations.

Please see figure about the pathway of the Gulf Stream: http://fuv.hivolda.no/prosjekt/ivartorepedersen/golfstroemmen.htm

The animals take up PCBs through the air, through the feed and through the skin. PCBs are fat-soluble and will therefore accumulate in the animals fat-reserves.

The polar bears are on the top of the food chain feeding mostly on seals. The levels of PCBs multiply through the food chain and are therefore higher in the polar bears compared to the other carnivorous animals at Svalbard. The levels of PCBs are also higher in cubs than in adults because of the large fat content in milk

Effects of PCBs

PCBs are toxins having several effects on the animals, the effects varies between the specific members of this group. In large doses it could cause acute death.

Norwegian scientists have discovered 7 polar bear females that have both male and female genitals, O. Wiig (1998), Science, vol. 280 (1998), number 5372, page 2053. They suspect that PCBs are the main reason for this development, through interfering with the hormone-regulating enzymes called P-450 cytochromes. The pseudohermaphrodites were not sterile since some of them had cubs.

PCBs have also an effect on the fertility of the animals. This is due to the fact that some of the molecules have a similar structure to hormones, and the can therefore mimic, block or disrupt the function of the naturally occurring hormones.

The authors opinion

The polar bears face several major threats due to human-interference. Not only are they vulnerable to toxins released into the environment, but they also face extinction due to melting of the sea ice in the Polar Regions. This is a very sad development since they are extremely fascinating and beautiful animals.

Sources:

http://www.environment.no/templates/themepage____2800.aspx

http://www.bellona.no/no/harde_miljoefakta/kjemiske_forbindelser/18781.html

http://www.sciencemag.org/cgi/content/summary/280/5372/2053b

http://www.polarbearsalive.org/facts.htm

http://www.toyen.uio.no/zoomus/forsk/isbjorn.html

http://www.destinasjontromso.no/gulfstrmmens_historie_eng.htm

http://fuv.hivolda.no/prosjekt/ivartorepedersen/golfstroemmen.htm

Hallgatói dolgozatok		Behaviour Server: http://www.behav.org
Student essays		Kabai Péter, peter.kabai+essay_ #_gmail.com (_#_= superdot)
		advice on essay

HIGH LEVELS OF PCB IN THE NORWEGIAN POPULATION OF POLAR BEARS By Kristine Bull Introduction The level of polychlorinated biphenyls (PCBs) in the Norwegian population of polar bears (Ursus Maritimus) at Svalbard is six timers higher than the American population and three times higher than the Canadian. The Russian population is the only population that has higher levels of PCBs. The high levels are believed to post the most acute threat to the population. To see a figure about circumplar levels of PCBs in polar bears please click on the below link: http://www.environment.no/templates/themepage____2800.aspx Polar bears The polar bears are the largest terrestrial predator on the earth. They live in the circumpolar north and scientist have estimated that there are about 22000-27000 animals today. 15000 of them live in Canada while there are about 2000 polar bears on the Norwegian islands of Svalbard. What are PCBs? PCBs are group of synthetic chlorinated hydrocarbons which are not easily degraded. They are not flammable and have isolating qualities which made them very popular substances. They were used in several electric systems and as an additive in paint and plastics. There have been developed 209 different types of PCBs and their toxic properties vary depending on the number of chlorine-atoms and the structure of the molecule. Even though PCBs are illegal today it is estimated that 2000 billion kilograms have been produced and about 1/4^th of it has already been released into the environment. Spreading of PCBs PCBs spread both trough air and water and are therefore found almost everywhere even though most of it, 60%, is found in the oceans. The reason that the levels of PCBs are higher in the Norwegian population than in the populations of Northern America might be that PCBs pollutions from other parts of the world are transported to Svalbard by the Gulf Stream. The Gulf Stream originates near Florida (US) and flow north passing Svalbard before it terminates in the Barents Sea. As the figure indicates the PCBs transported by the stream will not effect the Canadian and American populations. Please see figure about the pathway of the Gulf Stream: http://fuv.hivolda.no/prosjekt/ivartorepedersen/golfstroemmen.htm The animals take up PCBs through the air, through the feed and through the skin. PCBs are fat-soluble and will therefore accumulate in the animals fat-reserves. The polar bears are on the top of the food chain feeding mostly on seals. The levels of PCBs multiply through the food chain and are therefore higher in the polar bears compared to the other carnivorous animals at Svalbard. The levels of PCBs are also higher in cubs than in adults because of the large fat content in milk Effects of PCBs PCBs are toxins having several effects on the animals, the effects varies between the specific members of this group. In large doses it could cause acute death. Norwegian scientists have discovered 7 polar bear females that have both male and female genitals, O. Wiig (1998), Science, vol. 280 (1998), number 5372, page 2053. They suspect that PCBs are the main reason for this development, through interfering with the hormone-regulating enzymes called P-450 cytochromes. The pseudohermaphrodites were not sterile since some of them had cubs. PCBs have also an effect on the fertility of the animals. This is due to the fact that some of the molecules have a similar structure to hormones, and the can therefore mimic, block or disrupt the function of the naturally occurring hormones. The authors opinion The polar bears face several major threats due to human-interference. Not only are they vulnerable to toxins released into the environment, but they also face extinction due to melting of the sea ice in the Polar Regions. This is a very sad development since they are extremely fascinating and beautiful animals. Sources: http://www.environment.no/templates/themepage____2800.aspx http://www.bellona.no/no/harde_miljoefakta/kjemiske_forbindelser/18781.html http://www.sciencemag.org/cgi/content/summary/280/5372/2053b http://www.polarbearsalive.org/facts.htm http://www.toyen.uio.no/zoomus/forsk/isbjorn.html http://www.destinasjontromso.no/gulfstrmmens_historie_eng.htm http://fuv.hivolda.no/prosjekt/ivartorepedersen/golfstroemmen.htm

Notes (if any) by Peter Kabai:
Please note: although it might be useful to read essay examples on the Internet, do not use them as your source. Copy-paste patchworks are not torelated.