There are no effective boundaries when it comes to pollutants. Studies have shown that toxic insecticides that have been banned in many countries are riding the wind from countries where they remain legal. Compounds such as DDT and toxaphene have been found in remote places like the Yukon and other Arctic regions. This paragraph best supports the statement that

• toxic insecticides such as DDT have not been banned throughout the world.
• more pollutants find their way into polar climates than they do into warmer areas
• studies have proven that many countries have ignored their own antipollution laws.
• DDT and toxaphene are the two most toxic insecticides in the world.
• even a worldwide ban on toxic insecticides would not stop the spread of DDT pollution.