If you were fired because off your age, race, gender, national origin, religion or disability and can prove it or have evidence that you were terminated for any of these reasons, you have grounds to sue.
Whistle blowers are protected by law. You cannot be fired for exposing that your company violates a law or is commit an illegal act such as toxic spills. You will have to prove that your employers broke the law and you reported it, or that you were told to do something related to your work that violated a law and refused to do it.
Talk to an employment lawyer
You may have a cause for legal action.
If your employer made defamatory slanderous or libellous remarks about you caused your dismissal, you need to document the defamation. You will need proof.
You will win a wrongful termination claim if you are forced to quit your job because your employer has made your working conditions miserable.
If you are harassed at work, harassed, not just annoyed, you must prove the harassment was real and therefore was effectively a constructive discharge to win any wrongful dismissal law suit.