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Union Carbide’s King City Asbestos Mine, Largest in the World

Created by Union Carbide in 1963, the King City Asbestos Mine quickly became the largest in the world.  Located in California, the asbestos was discovered in 1957 by a Union Carbide employee.  The company estimated that they could mine the mountain for 4,000 years and not tap all the asbestos contained therein.  Union Carbide actively employed 450 people who mined chrysotile asbestos until 1985, making it also the last operating asbestos mine in the United States.

Union Carbide sold the asbestos mined from King City to manufacturers of building and construction materials including wallboard, paint, joint compound, and various types of adhesives.  The asbestos was added to these products to give them strength, and insulating and fire-proofing capabilities.  However, as we now know, asbestos causes mesothelioma—a deadly form of cancer.

These products were shipped worldwide and saw use across the United States up until 1978.  Hundreds of thousands of workers in the construction and remodeling industry have been exposed to asbestos from this mine alone.  After asbestos became untouchable in the 1980s, Union Carbide estimated that they were responsible for over 3,500 mesothelioma and cancer diagnosis per year. 

In 2004 a special report by LA Times reporter Lisa Girion cited tests that Union Carbide performed in the 1960’s on the safety of asbestos.  The report alleges that the company knew asbestos was dangerous long before they publicly acknowledged it. 

In fact, according to Art Valdez who spent 26 years working at the King City milling facility, which processed raw asbestos from the Union Carbide mine, the company told them that the type of asbestos they pulled from the mountain (chrysotile asbestos patented under the name Calidira) was “harmless.”  In fact, that exact word was used in a 1974 memo.

The official company position is that Calidira fibers are short enough to be expelled from the lung by breathing and coughing or to dissolve if they stay inside the body.  They cite the fact that not a single King City mill or mine employee has ever been diagnosed with mesothelioma.  However, Girion’s persistence unearthed company documentation that stated doctors did note symptoms that could be related to mesothelioma in three dozen individuals. 

However, the very nature of asbestos related mesothelioma is a protracted one.  The fibers can reside for decades within the lining of the digestive tract or in the lungs before they ever produces symptoms.  And by the time the symptoms arise, it may already be too late.  When it comes to asbestos, mitigating exposure is really the only true preventative measure that can be taken.

Many of the former employees of the King City mine and refining mill continue to be monitored by health professionals for symptoms of cancer, asbestosis, and mesothelioma.

Dow Chemical purchased Union Carbide in 2001 and assumed the financial responsibility of the company's asbestos legacy.