Welders working on San Francisco’s Bay Bridge were exposed for nearly a year to excessive levels of dangerous fumes — a condition the project's contractors apparently knew about and yet failed to either notify workers or correct the problem, state workplace safety inspectors found, according to the Alameda (Calif.) Times-Star.

During a nearly two-month inspection ending May 28, the California Department of Industrial Relations found serious health and safety violations, including ten months of worker exposure to manganese, welding and particulate fumes exceeding federal standards.

The workers affected were caisson welders working on the new bridge span and who were involved in the pile-driving operation by contractor KFM Joint Venture.

Cal-OSHA inspectors reported that KFM Joint Venture, a partnership of three construction companies, had been monitoring employee "breathing zones" and identified excessive exposure from May 2003 to March 2004. Yet apparently no corrective actions, including better ventilation and respiratory protection, were put in place until recently. Cal-OSHA also found that KFM Joint Venture failed to notify employees of the potentially harmful exposure as required by law, nor did it provide proper employee training regarding caisson welding hazards.

Other Cal-OSHA inspections found "serious hazards" relating to insufficient guard railing and other required safety measures to help prevent falls. Employees were exposed to more than 25-foot drops, inspectors found.

According to the National Safety Council, inhalation or ingestion of manganese dust or fumes can cause a wide range of symptoms including Parkinson's, insomnia, mental confusion, metal fume fever, weakness, paralysis, dry throat, cough, tight chest, flu-like fever, low-back pain and vomiting.

The hazardous conditions apparently came to light after ten former project workers, all of whom had been laid off, contacted Cal-OSHA to file informal complaints.