Good information on the following link regarding a very recent study published by Washington University in St. Louis.
Low levels of manganese in welding fumes linked to neurological problems
It pertains to manganese levels in weld fume, and how current exposure levels may be stated too high to effectively protect workers. This is important to know, because manganese exists in every form of carbon steel, therefore every welder is potentially exposed to the problem. The dangers have been known for a long time, but the Washington University study develops a case for lowering exposure levels to help ensure welder safety.
This is critical information to possess when making fume remediation purchasing decisions. Personal protection devices and general ventilation methods can be effective, but they may not be enough to protect workers from manganism and the family of health issues associated with it. Fume extractors have consistently proven to be the most reliable and effective equipment for controlling weld fumes.
As always, consult a professional industrial hygienist to monitor and evaluate their shop air to help determine the correct remediation steps. Industrial Hygienists can be found at https://www.aiha.org/about-ih/Pages/Find-an-Industrial-Hygienist.aspx