  A sequence of exact relations is found which connect one- and many-particle
time-dependent distribution functions of low-density gas with their derivatives
in respect to mean density. It is shown that, at least in the context of
spatially non-uniform gas evolutions, these relations forbid the "molecular
chaos propagation" and imply inapplicability of the Boltzmann kinetic equation
even under the Boltzmann-Grad limit and regardless of degree of the
non-uniformity.
