Yes, absolutely! There was even one episode where he and Dr. Blight held Captain Planet hostage so the Planeteers would bring him a lifetime supply of nuclear waste, when he could have just spent a weekend in France.

I imagine a rational Planeteer would try to determine precisely what does and doesn't qualify as "polluted" for purposes of their powers. Oil spills are bad for marine life, but would it be sensible for "too high a concentration of hydrocarbons x, y and z" to count as polluted? Then again, their powers aren't particularly reductionist: "earth" is a category of materials, hydrokinesis that cares about water content would need to contend with salinity and plankton, and "heart" is an incredibly high-level interface for emotions and neural processes, even across species with very different brains. (Wind suffers the same problems as water, but fire can get away with being a thermal energy hack.)