This is a characteristic which I look at when I buy new products. Many products are biodegradable, which is good. But that doesn't mean they won't hurt anything when these chemicals get washed into a local body of water. Any organic compound still contributes to the Biological Oxygen Demand (BOD) of that water body. As these compounds break down, bacteria in the water breathing through aerobic respiration use up dissolved oxygen (D.O.) which causes the D.O. level in the water to decrease. Less oxygen means that any other organism that utilizes that D.O. will be stressed. If the levels are reduced enough, die-offs will occur. That means fish, mussels, invertebrates, etc... These organisms are likely part of a large food chain including terrestrial animals as well, so the damage may not be limited to the body of water.
Things like engine degreasers and wheel cleaners are often harmful to the environment, but you can get around these. For engine degreasing, use something like 303 Aerospace Cleaner, which states that it is non-toxic, biodegradeable, and is safe enough to use full-strength to clean vegetables. When cleaning engines, I almost always clean them by hand, which greatly reduces the runoff of chemicals into the storm sewers.
As far as wheel cleaners, you will never have to use a wheel cleaner again if you clean the wheels very well and then use a sealant on them. They will always wash clean with ordinary soap and water. This reduces your personal contact with strong chemicals, and also reduces the potential damage of these chemicals to the environment.
When using a tire cleaner, opt for a diluted solution of 303 Cleaner for that too. I use a 10:1 (water:303) dilution and a scrub brush to clean my tires.
QEW is also a good choice for washing, because there is little to no runoff caused by washing with it.
