Medical benefits for Part Time Workers

I think this is a very important issue, because of the economy, and what has become the new world we live in. I feel there should be some type of law guarantees medical benefits for part time workers. My son has been employed at Giant Supermarket for five years, listed as part time, but scheduled work hours are full time, yet he has no medical coverage. There should be some compensations for employees. that have no choice but to accept this type of employment due to the lack of full time work. Without the risk of being terminated because they deserve medical coverage. Thank You