Very sorry about your husband. You should contact a workers' compensation attorney to investigate any rights you may have under the workers' compensation system, and also a personal injury attorney who can evaluate any rights you may have to a wrongful death claim against responsible parties for the chemical exposure.
Find a Workers' Compensation Attorney. Chemical exposure is a Workers' Compensation claim, and most states have death benefits for survivors. Workers' Compensation is generally the exclusive remedy in against an Employer in work-related deaths.
We offer general concepts, but you should give ALL your facts to a licensed Attorney in your state before you RELY upon any legal advice.