It is not so much an issue of clean industries, as of clean companies. Many companies claim to be clean or green, but few are. Take a look at a good one: 7th Generation, to get a sense of how a company can reduce toxic waste in manufacturing. It's also industry-specific. Not using bleach is important in paper-making, for example. Providing local food (to reduce fuel usage for food transport) is important in the grocery store field.