All commercially offered PCBs are made using ROHS conform components. No hexavalent chromium is added or used in any stage of the PCB assembly.
Unless specifically negotiated the PCBs have no clearance for life-support, aviation, nuclear, medical etc.
Explicit clearance as well professional in-field testing is required for these areas of application.
All PCBs are tested, and cleaned. Some flux residues may remain but they are harmless.
PCBs where possible (SMD parts) are assembled using infrared reflow process.