This thesis statement is not debatable. First, the word pollution implies that something is bad or negative in some way. Furthermore, all studies agree that pollution is a problem; they simply disagree on the impact it will have or the scope of the problem. No one could reasonably argue that pollution is unambiguously good.
Example of a debatable thesis statement:
At least 25 percent of the federal budget should be spent on limiting pollution.
This is an example of a debatable thesis because reasonable people could disagree with it. Some people might think that this is how we should spend the nation's money. Others might feel that we should be spending more money on education. Still others could argue that corporations, not the government, should be paying to limit pollution.
"In nature, nothing is perfect and everything is perfect. Trees can be contorted, bent in weird ways, and they're still beautiful." "Those who contemplate the beauty of the earth find reserves of strength that will endure as long as life lasts."