Can I sue my employer or L&I in Wa state?

Please note that my answer is not intended to establish an attorney-client relationship; and is limited based upon the information provided in your question. Generally speaking you cannot sue your employer for an injury caused at work in Washington State, with few exceptions. The facts as you have stated them, do not seem to support the exceptions, so no you cannot sue your employer. If the someone that mixed the wrong chemicals was a co-worker, or under the employer's control, you cannot sue the co-worker either. If the person was a third party, then you may have a third party claim, but more information would be needed. You also cannot sue L&I for the way it is handling your claim. It is not clear in your question what it is that you need that L&I is not giving you. You are entitled to: (a) treatment for conditions related to your exposure; (b) wage replacement benefits if you are unable to return to the same earning capacity due to the conditions related to your exposure- these benefits end when the claim closes; (c) vocational assessment, if supported by the facts; and (d) rating of permanent impairment when it is time for the claim to close. These are the broad benefits available under an L&I claim in Washington State. As to the concerns regarding L&I following you, it is possible that you are being investigated for fraud, if there is a concern regarding entitlement to benefits. However, this could just as likely be the employer and not L&I, or it may not be related to your claim. You should check to see whether your claim is under investigation. As to the opening of your mail, if you know for sure someone is opening your mail, this is likely a federal offense and you should report that person. As to the cancelled medical appointment, you have not provided enough information as to the type of appointment, who scheduled the appointment to begin with, and why it was cancelled.

I agree with the contents of the other answer. I would add that you can report safety concerns and/or violations to the Department of Labor and Industries by going here: http://www.lni.wa.gov/FormPub/Detail.asp?DocID=1784 Read the form's instructions, fill it out and submit it to the Department. Make sure to be very thorough when filling out the form so that the Department can understand the safety violation allegations. Good luck!