NEW BEDFORD — Representatives of local and state worker advocacy groups sent a letter last week to a city seafood processing facility detailing concerns about worker health. The letter, delivered April 19 in person and by email to North Coast Seafoods, discusses "troubling symptoms and illness" among current and former workers. The workers believe it is caused by a machine they say cuts and debones fish with hot water and pressure. "It produces and releases a smoke-like vapor that contains fish particulates. There has been some effort to channel the vapor out of the building, and while filters are used, they are often clogged," wrote members of Pescando Justicia, a 12-member committee of former and current seafood processing workers.