I have been breathing bat guano for several years at my job. They continue to do nothing. Do I have a case?

If you have a provable injury, then you may have a workers compensation claim.  You would need to speak to a workers compensation attorney about such a claim.  Those are injury claims and not within traditional employment law coverage.  If this is an unsafe condition, then you may be able to get the matter addressed by OSHA and would need to contact that agency.  You can do so via the agency's website. Otherwise, there are simply no employment laws that cover this situation.