  The exchange of light pseudoscalar quanta between fermions leads to
long-range spin-dependent forces in order g^2, where g is the
pseudoscalar-fermion coupling constant. We demonstrate that laboratory bounds
on the Yukawa couplings of pseudoscalars to nucleons can be significantly
improved using results from recent equivalence principle experiments, which are
sensitive to the spin-independent long-range forces that arise in order g^4
from two-pseudoscalar exchange.
