Every state (Including Illinois) has some theory of "warranty of habitability," meaning the landlord must provide the tenant with safe, livable premises. What this means is subject to interpretation state by state, but in general if the conditions violate local housing ordinances you may have a case. The situation (from an Illinois attorney) does seem to raise eyebrows.
Your rights as tenant would be (1) to leave and defend any future lawsuit for rent from the landlord based on the defense of warranty of habitability, or (2) stay and deduct from your rent the difference between the rent and "reasonable market value." Both of these options have risks involved and I would suggest speaking with an attorney before taking any course of legal action.
Christopher R. Minelli
Minelli Law Offices, LLC
NOTE: This answer is not intended to be legal advice and should not be construed in that way. This answer does not create an attorney-client relationship and no such relationship may be created absent a signed retainer agreement. The author is licensed in Illinois only, and his answer is for educational purposes alone.