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Merchant Marines - Mesothelioma Risks

During World War II, 200,000 mariners served on over 2,700 cargo vessels known as Liberty Ships, which were charged with supplying the war effort in Europe, Asia and North Africa. These vessels, built fast and cheap in shipyards along both coasts, were powered by steam reciprocating engines that used asbestos insulation. This exposure is now known to cause some very deadly diseases, including malignant mesothelioma.

Workers in shipyards where these freighters were built were exposed to high levels of asbestos during the construction process. So, too, were the seamen who later served aboard the ships. In times of peace these men are civilian mariners; but when America goes to war, these reserve ranks put on uniforms and become the Merchant Marines.

Asbestos was used in hundreds of ways on board Liberty Ships: in auxiliary equipment like the removable pads that were used to insulate literally thousands of flanges and valves found throughout each freighter; and in or around pipes, cables, gaskets, floor and ceiling panels, boilers, turbines, and exhaust systems. Asbestos application in rapid ship construction frequently involved applying insulation using high-pressure compressed air and insulating materials mixed with adhesives. Spraying this substance onto bulkheads left clouds of particles suspended in the air for hours or even days.


The heavy use of insulating materials in the engine rooms of cargo vessels served not only to fireproof the engine, but also to dampen audible sound, hampering the ability of enemy submarines to target the freighter based on acoustics.

The 45 to 80 crewmen, who were involved in maintenance and operation of each of these ships, were exposed to high concentrations of deadly asbestos dust on a daily basis; they run the highest risk of contracting mesothelioma. But dust travels: there was no safe place on board a Liberty Ship. From the galley to the bridge, from the crewmen's berths to the captain's cabin, these fibers were everywhere.

After the War, Liberty Ships continued to be used. Some were sold to U.S. allies; others became technical research or radar vessels. Greek shipping tycoon Aristotle Onassis built his fortune in part on the surplus Liberty Ships and Navy tankers he acquired from allied governments after the War. Few of these ships were upgraded; and for a generation asbestos exposure may have shortened the lives of merchant seamen on board these vessels.

The fast majority of Liberty Ships, however, were requisitioned as part of the National Defense Reserve Fleet. The U.S. government went to great pains to extend the working life of these vessels, launching a "Liberty Ship Conversion and Engine Improvement Program" in 1953. During this time, thousands more mariners may have been unwittingly exposed, therefore endangering themselves.

Asbestos has been linked to three extremely serious diseases. Asbestosis is a chronic inflammation of the lungs, brought on by inhaling asbestos dust. The fibers in this dust accumulate in the lungs where they cause scarring and fibrosis. While asbestosis is not invariably fatal, it is greatly debilitating: many asbestosis sufferers live out their lives on supplemental oxygen, and are forced to endure frequent, painful thoracentisis procedures. As well, it has been linked to lung cancers, either of the parenchyma or the pleural linings of the thoracic cavity.

The third disease, malignant mesothelioma, is a cancer affecting the tissues lining the body's serous cavities. Mesothelioma is the deadliest of all asbestos-related diseases: the average life expectancy for a patient with this diagnosis is less than one year. Typically there is a duration of 30 to 40 years between an exposure and the onset of mesothelioma. Liberty Ship veterans exposed decades ago may just now have begun to develop symptoms of asbestos-related disease. Over five thousand merchant marines lost their lives in World War II; unfortunately many more of them are dying today.

Workers at Risk for Asbestos Exposure

Below are a list of occupations and trades that were at risk for asbestos exposure:

Last Edited: Sun July 26, 2020