Sometimes we sweat the small stuff:
If you are thinking about putting a piece of found driftwood in a small tank with a $1500 prize fish, DON'T.
If you buy a piece of wood at your LFS, where did it come from? Was it boiled or otherwise treated?? After all, the FDA and EPA don't care what you put in your aquarium.
Boiling is a good idea - mainly because it kills living things (snail eggs, dragonfly larvae, etc). It MIGHT help remove some of the contaminants, but I wouldn't worry about it.
Gas and oil: The amount that gets into the water from boat traffic is minimal relative to the amount that would impact fish health. The main problem with these is the drinkability of the water. Boiling will remove gas, but not oil.
Pesticides: Again, drinkability is the main issue. Sometimes they can affect fish health, but usually this is an intermittent event (Joe tries to treat his own termites and uses 10x the label directions, then it rains that night). They might accumulate in the wood, but modern pesticides usually are degraded in the environment. Boiling in acidic solution can accelerate degradation.
Heavy metals (mercury, etc): Drinkability again. Long-term health of your captive fish might be a concern (mercury accumulates in fatty tissues and is a neurotoxin). Boiling will remove some, but many of these form slightly soluble compounds, so a series of boil/rinse/boil/rinse etc might be needed if the piece is really contaminated.
If you follow the EI method, the weekly water changes will keep any leachate levels low too.
72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias
2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.