Residual long-range pseudoscalar forces between unpolarised macroscopic   bodies
  In this paper we survey the effects of residual long-range forces associated to $\gamma_5$-spin dependent-couplings of fermions to massless bosons exerted by unpolarised bulk matter over macroscopic distances. We establish that such forces with behaviour proportional to $R^{-6}$ do indeed exist. They arise as a quantum mechanical effect due to simultaneous exchange of two quanta. We explore their presence in existing astronomical as well as laboratory data on non-newtonian components of the force between macroscopic bodies. Since no limits on their real existence could be found, we conclude that residual long-range pseudoscalar attractive and composition dependent forces between neutral unpolarised bulk matter extending over macroscopic distances are very efficiently shielded over a huge range of distances: from astronomical scales down to the micron scale. 
J.A. Grifols and S. Tortosa (IFAE Institut de Fisica d'Altes Energies   Grup de Fisica Teorica Universitat Autonoma de Barce...