  Nonlocal gravity has been shown to provide a phenomenologically viable
infrared modification of GR. A natural question is whether the required
nonlocality can emerge from perturbative quantum loop corrections due to light
particles. We show that this is not the case. For the value of the mass scale
of the non-local models required by cosmology, the perturbative form factors
obtained from the loop corrections, in the present cosmological epoch, are in
the regime where they are local. The mechanism behind the generation of the
required nonlocality must be more complex, possibly related to strong infrared
effects and non-perturbative mass generation for the conformal mode.
