See the Department of Public Health regulations on prisons and jails, 105 CMR 451, here.
Prisoners with concerns about unsanitary conditions may file a grievance with the prison administration about the problem and submit an appeal if the grievance is denied.
First, you should determine whether the problem you have identified is a violation of the Department of Public Health regulations governing prisons and jails. The Minimum Health and Sanitation Standards and Inspection Procedures for Correctional Facilities can be found at 105 CMR 451.001 through 451.503 and online here. If the problem is a violation of that code, you should be sure to state the specific regulation that it violates in the grievance you file with the prison.
You can also write a letter to the Department of Public Health telling them of this violation and asking for help in fixing it. You should give all details that you have about the problem. The address to write to is:
Division of Community Sanitation
Department of Public Health
305 South Street
Jamaica Plain, MA 02130-3597