There’s all kinds of controversy over what makes a car “green” and what doesn’t. Some point to size and efficiency, crucifying Hummers and full-size trucks as criminals against the planet. Others point to lifecycle greenhouse gas emissions, battery-component mining pollution and other less-obvious measures to excoriate hybrids. In any case, TTAC’s scientific department isn’t well-funded enough to issue a comprehensive report on the subject. Forbes may not have tested cars itself, or dug into true “dust-to-dust” footprints, but it’s gone ahead and published a list of “America’s Dirtiest Vehicles” anyway. Let’s take a look, shall we?