THE TOXIC EFFECTS OF HARMFUL POLLUTANTS - SUCH as DDT and PCBs – have long been known to researchers, but the extent to which they travel in our environment is causing increasing global concern.

One study, for example, found that pesticides used in southern China found their way into seals in the Canadian Arctic. Upon eating the seals, Inuit people of the region also ingested the pollutants – some of which ended up in the breast milk of Inuit women.

In response to this growing problem, chemistry professor Frank Wania of the University of Toronto at Scarborough is at the international forefront of researchers who are looking deeper into these pollutants – called "persistent organic pollutants" or "POPs" – and their dangerous journey.

Wania and others have recently begun to understand the migration of POPs. The following are the basic components:

• Warm temperatures in temperate, tropical and subtropical regions allow for harmful pesticides and industrial chemicals to evaporate into the atmosphere and migrate north and south to the earth’s polar regions.

• POPs can migrate in a series of short jumps, called the "grasshopper effect." They migrate, rest, and migrate again in tune with seasonal temperature changes at mid-latitudes.

• Cooler temperatures at higher latitudes enable deposition of the pollutants from the atmosphere onto soil and water and slow their evaporation back into the atmosphere.

• Decomposition of the chemicals slows down in colder climates, allowing POPs to remain intact longer.

• With the cold allowing the POPs to remain in water and soil, they are eventually consumed by animals and humans. "It’s not easy to understand," says Wania. "There are many aspects of the migration that still need to be analyzed. So my goal now is to calculate exactly the origins and pathways of these migrations."

He and his colleagues have been developing what is called a "global scale model" that tracks the journeys of various harmful chemicals around the world. To gather information for the model, Wania uses air samples from monitoring stations he has set up in remote regions across Canada and from the Arctic to Costa Rica.

With funding provided through Ontario’s Premier’s Research Excellence Awards (PREA) and the federal Department of Indian Affairs and Northern Development, Wania’s next steps will be to refine the model and to uncover new information, such as the role of ice and snow in the migration process.

Wania sees two main benefits of his research. "First, Canada and other countries will be better able to control these contaminants by scientifically tracking where they come from, where they go and how they get there.

"The information will also provide guidelines for industry, as it tries to design new, safe chemicals or substitutions for existing products." This kind of research promises to have an important impact on the global effort to protect the environment – and the life that it supports.

– Paul Fraumeni