Will the JWST be affected by dust at L2 (gegenschein?) Gegenschein is a "faint brightening of the night sky" at the anti-solar point.  A naked eye limiting magnitude of about 7.6 might enable an observer to make out gegenschein.

The Wikipedia article on gegenschein suggests that interplanetary dust at the Sun-Earth L2 point might be responsible for gegenschein.

The James Webb Space Telescope will also be at the Sun-Earth L2 point.

Does this imply that the same interplanetary dust that may be responsible for gegenschein will affect the JWST?
The Wikipedia article cites "Zdeněk (1962)" for the statement that the dust responsible for the Gegenschein has a possible concentration at L2. I haven't been able to obtain that paper, but I can't really see why that would be the case, since L2 is not dynamically stable.

However, the dust consists of millimeter-sized grain (see e.g. this APOD image), which is quite large for dust. Such large grains probably has a highly anisotropic "phase function", with a high preference for backscattering. Since when you look from Earth toward L2 you have the Sun in your back, you will thus see an increased brightness compared to other directions, even though the density of that dust is the same.

If this is the case, then placing JWST in L2 is no problem (except when it looks exactly away from the Sun, but that would be a problem anywhere in the ecliptic).