The companies that manufactured, sold and installed asbestos products had extensive knowledge of the deadly hazards of asbestos as early as 1920. Yet, these corporations waited decades to provide warnings to workers and to the general public. In some cases, warnings were never provided.

In addition to this actual knowledge on the part of asbestos corporations, the evidence available in medical books and journals revealed the dangers of asbestos exposure long before millions of American workers were exposed.

Here's a brief timeline of the known dangers:

Late 1800's: The first reports of lung disease in people working in asbestos factories.

1918: US government report stating that it was the practice of American and Canadian life insurance companies not to sell coverage to asbestos workers due to the assumed injurious health consequences. A reference reports that the Chief Inspector in England is aware of deaths and lung disease in workers at asbestos plants.

1924: British medical journal publishes first widely available article describing death of a 33-year old woman who worked in an asbestos textile plant.

1927: A pathologist issues a report describing asbestosis as a disease that involves the scarring of the lungs and shortness of breath. The report indicates that asbestosis could be fatal.

1928: Journal of the American Medical Association publishes editorial called "Pulmonary Asbestosis." Articles and case reports describing incidence of asbestosis are published in the United States and worldwide.

1930: Dr. Merewether, a famous researcher, publishes first clinical examination of hundreds of workers in the asbestos industry. He found that one out of four workers was suffering from asbestosis. Dr. Merewether further concluded:

• That asbestosis was a disease of latency, i.e. that workers exposed to asbestos wouldn't show signs of injury for many years;
   
• That asbestos dust had to be controlled through ventilation and the use of respirators.
   
• That workers exposed to asbestos should be informed and warned in order to assure a "sane appreciation of the risk."
   
• That the finished products created dust that should be controlled and minimized.

Dr. Merewether's medical description of asbestos disease mirrors exactly the description of the disease today. His recommendations, if implemented by the asbestos industry, would have saved tens of thousands of lives and injuries to American workers.

1930s: Reports demonstrated that asbestosis was occurring in workers with as little as nine months of exposure.

1933: First American case report of asbestosis in an insulation worker.

1934: Researchers report cases of asbestosis and lung cancer in an asbestos factory. Many of the workers had less than six months of exposure to asbestos. Reports were also published of asbestosis from workplace exposure to products, including boiler workers, custodians and insulators.

1942: Researchers report that lung cancer in building trades workers is likely caused by asbestos. Dr. Heuper, a noted occupational physician and the first chief of the environmental cancer section of the National Cancer Institute, suggests that asbestos causes Asbestosis as well as cancer in the manufacturing process as well as through finished building products such as insulation and packing materials. In 1949, Dr. Heuper warns that asbestos was a cancer risk to the general population. By this time there were over 200 references in the widely available literature regarding asbestos and disease.

1943: First case of a mesothelioma-like tumor reported.

1947: Dr. Merewether finds that 13% of asbestosis cases also had cancer of the lungs or pleura.

1949: Encyclopedia Brittanica lists asbestos as a recognized cause of occupational and environmental cancer. The Journal of the American Medical Association concludes that asbestos is probably linked to occupational cancer.

1953: Mesothelioma is reported in an asbestos insulator.

1955: A major epidemiological study demonstrates that asbestos workers have a tenfold risk above the general population of contracting lung cancer.

1960: Another epidemiological study confirms reports that exposure to asbestos causes mesothelioma. This study also included the children and wives of asbestos workers who contracted mesothelioma.

1964: Dr. Selikoff, a major researcher at Mt. Sinai Hospital in New York, confirms widespread disease among asbestos workers and from family members living with asbestos workers. A large number of job titles were implicated in the report, including construction workers, electricians, plumbers, carpenters, etc. Selikoff pointed out that asbestos did not "respect" job titles and could harm any person who breathed in asbestos.

After 1964, the medical literature continued to identify asbestos as a major carcinogen and environmental hazard. Over 200 publications described the hazards of asbestos by the end of the 1960's.

Notwithstanding this knowledge, and the death that resulted from breathing in the dust from these products, the manufacturers and installers of these materials continued to sell and install asbestos products without warning workers, reducing the dust or substituting equally effective materials in place of the asbestos. Tragically, many companies had secured additional knowledge regarding the connection between asbestos and cancer as early as the 1930's. However, these companies altered research reports to hide these findings from the public.