Is there a law in the state of michigan that requires breaks at work?

YES IN EVERY STATE... YOU ARE REQUIRED BY LAW A 30 MINUTE BREAK IF YOU WORK FULL TIME 8 HOURS OR MORE AFTER 8 HOURS YOU ARE REQUIRED 15 MINUTES FOR EVERY TWO HOURS AFTER THE 8 HOURS
There are laws like that in every state.


Answers:
Yes.
It's a federal labor law. Usually 15 minutes for four hours of work or 30 for eight hours. Some contractual jobsmay differ if a company offers a different plan as long as it is in the favor of the employee and not the company.
The US Department of Operational Safety and Health Administration (OSHA), a Federal Program, mandates breaks at work (more most types of full time and part time employment). These rules apply to every state, including Michigan (where I am from). OSHA requires a fifteen minute break for every 4 hours of work completed and a half hour lunch break for every 8 hours completed. So, if you work a 12 hour job, you should have two 15 minute breaks and 1 half hour lunch.
http://www.dol.gov/esa/programs/whd/state/meal.htm
http://www.dol.gov/esa/programs/whd/state/state.htm

There is no federal law requiring that employees--salaried or hourly--receive breaks during work time

Arizona law does not mandate rest and meal periods for employees. Neither does Maryland or Michigan law. Thus, it is important for employers to check their particular state's laws for requirements, if any.

http://www.entrepreneur.com/article/0,4621,305520,00.html