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Air Sampling Research

What are POPs?

Persistent organic pollutants (POPs) are chemicals that have been made by humans or result from human activity. There are three general categories of POPs:

Pesticides (DDT, chlordane, heptachlor, and five others):
Produced to be toxic, in order to improve agriculture production by killing pests and to kill insects carrying diseases such as malaria and typhus. DDT is one of the most popular toxic chemicals and has been widely used from 1940’s to the 1980’s.

Industrial chemicals (PCBs and HCB):
Designed for industrial uses, such as in electrical transformers and capacitors, in paints, in fireworks and plastics.

By-products of other processes (Dioxins and Furans):
Not produced intentionally; serve no useful purpose.
They occur by the burning of materials containing chlorine, such as PVC (vinyl) plastic, bleached paper, paint strippers.

As the name of these chemicals tells you, they are very persistent in the environment and degrade, or break-down, very slowly. In fact, once POPs are released to the environment they may be present for several decades.

A special property of POPs is to love fats (what scientists call to be lipophilic), that means they bind with these fats resulting in an accumulation in the fatty tissues of living organisms. They get into the food web as animals are eaten by other animals. POPs become more concentrated as they move from the bodies of smaller prey to larger predators. The top-level predators, such as whales, polar bears, and humans, can have higher levels of POPs than the animals making up the basis of the food web.

Many studies have shown that POPs can be harmful to wildlife and humans. POPs are related to damage to the nervous system, to the liver, and to reproduction system. There may be a connection between cancer and some POPs.

Now, you may ask yourself, why whales and polar bears have high levels of these pollutants in their fat tissue, because in their habitats their should not be any release of POPs into the environment. However, POPs appear in places where they have never been used. It is because of the fact that POPs like to travel and scientists call the process "global transport". POPs evaporate (means change into vapor) at warm temperatures from contaminated soils and waters into the atmosphere. The vapor travels in air currents of the atmosphere around the globe. When the vapor cools, it settles on the land and water again and POPs travel aligned with seasonal temperature changes, as a grasshopper jumps around. In fact, "the grasshopper effect" is the name for the way POPs are able to travel. POPs move thousands of kilometers from the warmer latitudes of our planet, such as the tropical regions of Southeast Asia (where they have been widely used) to the cooler latitudes as far as to the Arctic and Antarctica.

During the Jocara Indian Ocean Quest, air samples were collected on various places along Jocara’s route to determine the levels of POPs in the air over the Indian Ocean. In three previous studies from the mid 1970’s and beginning of 1990’s conducted by scientists from Japan and USA the levels of POPs, in particular of the two pesticides DDT and HCHs, were very high, likely due to the high usage of pesticides in India and Southeast Asia three decades ago. With this study scientists from the Tropical Marine Science Institute/National University of Singapore and the crew of Jocara wanted to show if there has been a significant decline of the levels of POPs over the Indian Ocean after the ban of these chemicals in many countries of Asia, including India in the beginning of 1990’s.

In general, the levels of DDT has declined over the past 30 years, in particular over the open ocean. Relative high levels along the Indonesian coast may be an evidence for the ongoing usage of DDT in this region. HCH, another widely used pesticide, is hundred times lower nowadays compared to data from the 1990’s, when the highest level has been detected at a time of the ban of this chemical in India. The levels of the industrial chemicals PCBs has been detected at relative low levels, even 30 years ago. However, the region of the Indian Ocean is less industralized compared to regions in Europe and North America, but with extensive agiculture activities. However, higher PCB levels has been detected nearby a large UK/US naval base at the Chagos Archipelagos and over the Atoll from the Maldives with a population of 28,000. People on the Maldives often burn their household waste in the backyards resulting in an uncontrolled air pollution. Scientists has been reported earlier, that soil were contamianted with PCBs nearby militry bases and therefore our findings are not a surprise.

Overall, the region of the Indian Ocean with adjacent countries of high consumption of POPs in the past is significant less contaminated with atmospheric POPs, but may still be a source for the global distribution of these chemicals.

More about the air sampling research.

 

 
© JIOQ 2004, 2005
 


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