I own an environmental consulting company, and this is what we recommend to our clients, even though it means they may have less need for our mold consulting services.   

Taking the money of hard working Americans and giving it to the bankers; socialists; radical environmental causes (like the proposed cap and trade); and taking ownership in our largest companies is particularly offensive.

However, you guys shouldn't be so quick to dismiss Nobel, I hear W 43rd was lined up for a Nobel of his own for outstanding environmental work (excellence in brush clearing while holding highest office) but unfortunately that didn't go through...

Oil spots large enough can be tracked into the house and ruin the carpets, they make the curb appeal look bad and are an environmental hazard that could get you fined by the city.

If you do most of the above, you can advertise your rental as water and energy efficient- most tenants will only care about the money they save, but being environmentally friendly is desirable to some small subset of people.

If anyone is masochistic enough to be looking for an exercise or case study in this, look up the Federal Realty Investment Trust project at Assembly Square in Somerville MA:  a former Ford plant turned barren wasteland with (over time) multiple environmental matters on site to clean up.   

Is an environmental assessment necessary?

Environmental Works is a company who my husband (an agent) routinely recommends and works with. 

For this lot, we did all the environmental studies, grading plans, fire approvals, and landscaping plans, along with a preliminary architectural design since it helps with the sale if the buyer can "see" themselves living in the property.

Also, Environmental Engineering will also be a long term asset as that is another area impacts real estate deals.