There is plenty of evidence that atmospheric molecules DO escape into space, but what the total quantity is per year is not so clear.
Not only that but the information is getting old. The quantity of gasses escaping the atmosphere could be less today or it could be more, we’ll never know unless more research I conducted.

Date: December 9, 1997
From
http://science.nasa.gov/newhome/headlines/ast09dec97_3.htm

To Chappell's surprise, the real find was around the north pole where RIMS measured gases flowing upward from the ionosphere into space as DE-1 arced to about 4.6 Earth radii above the pole (the orbit was 464 x 23,370 km [288 x 14,490 mi]).
"The more we measured it," he said, "the more we realized that this was a big source of material." RIMS measured ions of hydrogen, helium, oxygen, and nitrogen rising at different speeds and on different trajectories.
Apparently, the particles that slammed into the ionosphere to paint the aurora borealis also energized enough atoms to head spaceward. (The same is true of the south pole where DE-1 made similar observations.) The acceleration mechanism is not fully understood, though. Giles said that very low frequency (VLF) radio waves, emitted in the magnetosphere, may contribute energy.

Snip

"And lo and behold, there's all this low-energy plasma flowing out of the atmosphere and into the magnetosphere," Chappell said. Some of the material does fall back to Earth, mostly the heavier ions with low energies, but enough apparently is accelerated to reach into the tail of the magnetosphere.
TIDE expanded on RIMS's measurements and showed that the ion flow starts with very low energies, down to a few tenths of an electron-volt, and that its altitude is twice as high as DE-1's orbit.
"The really incredible thing," Chappell said, "is that if you do a very careful model of the magnetic field and electric field, and then put in 10 eV particles, they go into the plasma sheet, and are energized at least a thousandfold.".

Snip

"We're not starting with a solar wind particle at 1 keV," Chappell sad, "but with atmospheric particles at a few eV. They make up everything you see up there.".

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Date: Jan. 7, 1999

However, the auroral fountain is spewing all the time, even without the sun helping things out.
"The main question is, How do these very low-energy particles defy gravity and get to those altitudes?" said Coffey..

In the early 1980s, scientists at NASA/Marshall, using an instrument aboard the Dynamics Explorer-1 (DE-1) satellite, discovered that the upper ionosphere is heated by electrical currents to form a "polar plasma fountain" of oxygen and hydrogen ions.
Follow-on studies by the Thermal Ion Dynamics Experiment (TIDE) aboard the Polar spacecraft, launched in 1995, have shown that the fountain rises higher than the DE-1 could measure. Indeed, the evidence is building that Earth's magnetotail is filled with ions not from the solar wind but accelerated upward from Earth's own atmosphere..

Date: Dec. 8, 1998

Some plasma and all fast atoms are permanently lost from the ionosphere to the downstream solar wind while much of the plasma outflow is recirculated through the magnetotail neutral sheet and accelerated to form energetic plasmas.

http://spacescience.spaceref.com/newhome/headlines/ast08dec98_1.htm