What was the real cost of your last seafood meal? Marine workers, past and present, face a multitude of medical threats unique to a life at sea.
Harvesting the resources of the ocean comes with a health warning. Oriol Salvador/Flickr (CC BY-NC-ND 2.0)
Oceans do a lot for us: beyond beauty and inspiration, they contain a wealth of valuable resources from tuna to natural gas. We use oceans to move vast quantities of products and raw materials all around the world. But these services come at a cost. To access these benefits, people have to work at sea.
Many oceanic occupations rank among the world's most dangerous jobs, reflecting both the remoteness of the workplace and the relatively high risk of injury and illness. In the late 19th century the number of deaths aboard British merchant ships was reported to be “six times higher than for underground coal miners, nine times that for railway workers, and 146 times that for factory and shop workers”. Marine workers are faced with a diverse and unique collection of health hazards, from shipwrecks to rotted fish burps.
One of the major causes of death among early sailors was scurvy, a disease caused by a prolonged deficiency in vitamin C. Ship rations often prioritised low cost foods with a long shelf life, which generally ruled out anything rich in the vitamin. In afflicted sailors, scurvy weakened the connective tissues holding together various parts of the body. Their capillaries would rupture, spilling blood where it shouldn’t be – under the skin, forming large purple spots; out of the nose; and into the urinary and digestive tracts, resulting in bloodstained urine and faeces. Their gums swelled and went spongy, releasing their hold on teeth. Wounds and broken bones failed to heal properly, while joints became stiff and painful. Ultimately, the disease was fatal.
The symptoms of scurvy, from the journal of Henry Walsh Mahon (1841-2). The National Archives UK/Flickr (public domain)
Although the British Navy managed to get a handle on scurvy by the start of the 19th century by providing sailors with citrus fruits, it continued to plague merchant shipping fleets for several more decades. The disease finally loosened its hold on sailors once steam engines sped up travel times, and access to good quality lime juice (filled with vitamin C) was widely introduced.
Unfortunately, there are no easy cures for another long-standing health problem in sailors: skin disease. The close quarters of a ship are highly conducive to the spread of contagious agents looking for a tasty dermal meal, be they bacteria (impetigo), fungi (athlete’s foot), lice (crabs) or mites (scabies).
During the Second World War, Allied sailors were also subjected to several irritating materials encountered aboard a warship: engine oil, rough wool uniforms, and the brutally strong laundry soap used for personal cleaning – some varieties of which were reportedly strong enough to remove “even paint from the deck”. Each of these irritants proved severely disagreeable to the epidermis of at least a few unfortunate souls, to the point that they had to seek medical attention.
In addition to the perils of warfare, sailors during the Second World War also battled the health consequences of life at sea. Lt HW Tomlin/Wikimedia Commons (public domain); Lt RGG Coote/Wikimedia Commons (public domain)
Skin infections also plague saturation divers who make a living inspecting and maintaining the underwater components of offshore oil and gas platforms. When working deep below the ocean’s surface, the divers live in steel chambers with a pressurised atmosphere. Their living spaces are hot and humid, with temperatures often hovering around 30°C and the relative humidity occasionally reaching upwards of 80%. In other words, fantastic growth conditions for many bacteria capable of infecting a person’s skin.
One such bacterium, Pseudomonas aeruginosa, can cause face, neck and external ear infections, and a painful and disfiguring condition known as “diver’s hand” involving “extensive skin peeling of the upper skin layers of the palms of the hands and occasionally of the soles of the feet”. P. aeruginosa can get into the chambers' freshwater systems and persist for months at a time, potentially infecting divers when they shower. It’s a hardy microbe, making it a challenge to control in the best of scenarios, let alone in an isolated, pressurised chamber.
In the early 1960s, Canada was discovered to be a world leader in rates of lip cancer. Taking a closer look, researchers realised the incidence of this cancer was substantially higher on the island of Newfoundland compared to other parts of the country. At the time, the economy of Newfoundland was dominated by the fishing industry, and cancer rates were highest among those living along the coasts. This suggested that being employed on a commercial fishing vessel was an important risk factor for lip cancer.
Fishermen in Newfoundland, Canada during the 1970s had a high risk of contracting lip cancer. Anton Likanov/Flickr (CC BY-NC-ND 2.0); Derek Keats/Flickr (CC BY 2.0)
In 1975, a study published in the New England Journal of Medicine confirmed the link. The authors observed that some of the workers who handled the fishing nets, which were coated in what was likely a carcinogenic tar, would hold the nets with their mouths if their hands were otherwise occupied. Naturally, they suspected this group of workers would be more likely to develop lip cancer, but this wasn't the case. Instead, spending a lot of time in the sun, as many people do while working aboard a ship, appears to be a key risk factor for lip cancer.
If you harvest spiny lobsters off the Pacific coast of Japan for a living, there’s a chance your job will make it difficult for you to breathe. A soft red coral called Dendronephthya nipponica tends to accompany the lobsters on their journey from seafloor to ship deck via dragnet. As those aboard fishing vessels work to release the catch, they find themselves in close proximity to ensnared coral. For some, repeated exposure to Den n 1, an allergen present in the coral, causes their immune system to mount a massively overblown response, leading to red eyes, runny noses, rashes and asthma.
A similar scenario plays out off the east coast of England in a shallow, sandy-bottomed region of the North Sea known as the Dogger Bank. Trawler crews dragging their nets along the seafloor in pursuit of cod and herring can inadvertently scoop up the bryozoans Alcyonidium diaphanum (previously A. gelatinosum) and A. hirsutum . These gelatinous marine animals contain a toxin that causes an oozing, itchy skin reaction known as the Dogger Bank itch.
Commercial fishers around the world face a suite of species-specific threats. Allen Shimada/Wikimedia Commons (public domain)
In addition to allergic reactions to sea life, fishers must also prepare against fatal gas accidents. The hold of a large fishing vessel can become a prospective tomb if it is filled with fish and these fish are permitted to rot. Bacteria consume the fish and burp out carbon dioxide and hydrogen sulfide, neither of which is particularly amenable to human life. Workers who unknowingly enter a hold full of these gases can quickly go unconscious and die as their cells are denied both oxygen and the ability to use it to generate energy.
Although the sea can be a perilous place to work, the tasks carried out by those employed away from shore are seen as a necessary part of maintaining the modern life. Ocean jobs keep seafood on our menus, goods in our stores, and gas in our cars. Many of the illnesses and injuries affecting marine workers are specific to the jobs being done, but they’re all part of the price they pay to get paid to utilise the sea.
Edited by Andrew Katsis and Ellie Michaelides
