  The most important problem of fundamental Physics is the quantization of the
gravitational field. A main difficulty is the lack of available experimental
tests that discriminate among the theories proposed to quantize gravity.
Recently, Lorentz invariance violation by Quantum Gravity(QG) have been the
source of a growing interest. However, the predictions depend on ad-hoc
hypothesis and too many arbitrary parameters. Here we show that the Standard
Model(SM) itself contains tiny Lorentz invariance violation(LIV) terms coming
from QG. All terms depend on one arbitrary parameter $\alpha$ that set the
scale of QG effects. This parameter can be estimated using data from the Ultra
High Energy Cosmic Rays spectrum to be $|\alpha|<\sim 10^{-22}-10^{-23}$.
