Beta Radiation Elevated in WTC Dust

A short section buried in the EPH report:

We found only background levels of alpha radionuclide activity by liquid scintillation counter analysis of all three samples. Beta activity was slightly elevated, but not more than twice the background level. There were no levels of gamma activity > 1 Bq/g except for naturally occurring potassium-40.

Note also this from the report:

When placed in the liquid scintillation fluid, the WTC samples are somewhat darker than the backgrounds and calibration standard, which may cause slight underreporting of the beta activity due to quenching and standard-to-sample efficiency bias.

This radiation is unlikely to be Radon, a relatively common radioactive element fond in building materials, as Radon emits alpha, beta and gamma radiation.

However, tritium is solely a beta-particle emitting radionuclide-- and of course tritium is a by-product of nuclear fusion reactions.

We already know they found tritium at Ground Zero-- was it found in the dust too?