Another benefit is that it will block [alpha radiation][1] (helium nuclei) and most of [beta radiation][2] (electrons).

![](http://www.bbc.co.uk/schools/gcsebitesize/science/images/116_radiation_penetration.gif)

You can read more [here](http://www.blackcatsystems.com/GM/articles/alpha_beta_gamma_radiation.html).

[1]:http://en.wikipedia.org/wiki/Alpha_particle
[2]:http://en.wikipedia.org/wiki/Beta_particle