Workers in shipyards have been, and still are, exposed to toxic substances, some of which are carcinogenic and have become notorious. The most important of these are fibres and asbestos.
Asbestos is used in various forms in ships, in particular chrysotile (white asbestos) which is present in insulation and in Klinger jointing sheets. Fibres from this known carcinogen are also present in flooring in engine rooms and living quarters (20). It causes specific respiratory diseases. These can be benign conditions of the parietal pleura (pleural plaques) and of the organs (benign pleurisy, fibrosis) or a form of pulmonary fibrosis called asbestosis. However, it can also cause malignant conditions such as primary malignant mesothelioma, cancers of the bronchi and lungs and, less specifically, cancers of the digestive, urinary or genital regions (kidney and ovary) (21, 22). In France in 2001, 3,354 cases of occupational disease linked to asbestos exposure were declared, including 2,351 pleural lesions and 479 cancers. Smoking, a significant carcinogenic factor, plays a role in these declared illnesses. The activities that involve the most exposure are cutting and removal of insulation, with exposure in the 1960s and 1970s of between 1.1 and 132 f/cm3. For fitting joints, exposure is estimated to be between 0.03 and 0.28 (23). Ambient levels in various parts of the ship were established by combining the results of 52 metrology studies involving 84 ships between 1978 and 1992. Mean atmospheric levels were between 0.008 and 0.004 fibres/cm3 in the crew’s living quarters. The highest levels were observed in engine rooms, with mean concentrations of 0.01 (20). There is therefore environmental exposure when carrying out repairs on board ships, but this remains lower than recommended limits. Workers employed in shipyards before 1980 suffered heavy exposure. In a study of 18,211 North American metallurgy workers, shipyard work represented a 1.85-fold increased risk of asbestos-related disease (24). This was confirmed by long-term follow-up, between 1966 and 1975, of 253 workers in a British shipyard. Seventeen deaths from asbestos-linked malignant disease were observed, and pleural plaques were present on the chest X-ray in 21% of these workers (25). The extent of exposure was significant; between 1999 and 2005 there were 1,879 declared cases of asbestos-linked occupational disease in one French shipbuilding yard. 22% of CT scans carried out routinely on workers over 50 showed disease (plaque or pleural thickening). The occupations with the most exposure are boilermakers (27%), pipefitters and welders. Those who worked in shipyards before 1980 must be monitored carefully, but this should not obscure the fact that there is still a risk, mainly in ship repair. Close attention should still be paid, as refractory ceramic fibres used as a replacement for asbestos have similar biopersistance characteristics and are classed as 2B carcinogens by the IARC. In a recent study, Bianchi included 2776 people who worked in monfalcone shipyards in 1942. In this population, 18% have a diagnosis of mesothelioma and in the population of 14 years old workers in 1942 (557 workers), 6 have declared mesothelioma (26).
Another concern in terms of prevention of chemical risk are high levels of exposure to hydrocarbons in various forms. Aromatic hydrocarbons are found in solvents that contain toluene and xylene (43[jc1] % of boatbuilding workers exposed, NIOSH 1982) and these are widely used by engineers and painters, as is styrene, which is used in boatbuilding(1). These are central nervous system depressants, and carry a long-term risk of diseases such as attention-deficit-hyperactivity-disorder. They are irritant to the skin and respiratory system, and in large quantities carry a risk of pulmonary oedema, anorexia and abdominal problems. Toluene is classed as a teratogen and carcinogen class 3, and kidney conditions such as glomerulopathy have been described (27, 28). Exposure to carcinogens such as benzene (a leukemogen) and trichloroethylene (which causes kidney cancer) also occurred before these substances were banned (29). Occupational exposure can be direct (use of a product) or indirect, via the products being transported (petroleum derivatives) (30).
Styrene is used in the polymerisation of polyester resins, and represents 40% of the weight of these resins (1). It is classed as a 2B carcinogen by the IARC, because of the possible risk of effects on the blood.
In painting, there is exposure to aromatic solvents such as xylene and toluene, which are present in paints and solvents used to clean equipment. There are also ketones, aldehydes, esters and glycols. Low molecular weight hydrocarbons are asphyxiants and central nervous system depressants. As exposure is increased when work is done in confined spaces (in ballast tanks and fuel tanks), as demonstrated by Kim, with mean levels of 12, 28.23, 4.6 and 3.03 ppm for toluene, xylene, methyl ethyl ketone and glycol ethers, which were 4 times higher than for painters working on deck (31). In a south-korean shipyard, Fifteen exposed spray painters, 19 sandblasting workers and 30 office workers non-exposed were recruited for this study. In environmental sampling, mean of values of xylen and ethylbenzen were respectively at 1.25 ppm and 2.25 ppm. Associated with atmospheric assessment, they made urinary biomonitoring of mandelic acid, methyl Hippuric acid and 8 oh-hydroxydeoxyguanosine In results, urinary methylHyppuric acid increased significantly when comparing pre and postshift. It was the same for 8 oh-hydroxydeoxyguanosine results between preshift and holidays. Ansd a significant correlation was found between urinary 8-OHdg and the exposure to ethylbenzene. The occupational exposure to paint seems to increase oxidative DNA damage (32).
Ethylene glycol acetates carry a risk of haematological disorders such as bone marrow depression (31). One practice which seems still to be taking place is hand-washing in solvents. Painters may thus have been exposed to high concentrations of trichloroethylene until the 1990s; a definite carcinogen according to the IARC,. In addition to high proportions of xylene, anti-corrosion and anti-fouling paints contain epoxies (which cause skin sensitivity), pigments and antifouling molecules. Since tributyltin (TBT) was banned in 2003, pigments mainly consist of copper oxides, and zinc, titanium, nickel and iron oxides. These pigments irritate the respiratory tract, and copper is suspected of causing an increased risk of cancer of the urinary tract. Other biocides used are Diuron, Irgarol 1051, Sea-Nine and dichlofluanid[jc2] . There is little human toxicology data on these substances, apart from one study which showed respiratory sensitisation chlorothalonil (32). Respiratory exposure experienced by ship painters was evaluated, and exposure to copper was 3 mg/m3 for spray-painting and 0.8 mg/m3 for sandblasting, 0.14 for Dichlofluanide (33), and 52.6 and 33.2 ppm for xylene and ethylbenzene respectively. Grandjean found blood and plasma nickel levels of 5.2 µg/dL in a population of ship painters, levels that were statistically greater than for a group of welders (34). When following up painters in this sector over the long term, prior exposure should not be neglected. Examples are trichloroethylene, mentioned above, Coal Tar, which carries a risk of skin cancer, asbestos in Bitumen/latex paint and crystalline silica, which carries a risk of pneumoconiosis and lung[jc3] cancer for silica and bronhopulmonary cancer for asbestos. Lee showed that painters were exposed to coal tar, and found high levels of hydroxypyrene (2.24 µmol/mol of creatinine) that were statistically greater in these groups than in painters who were not exposed to coal tar. Lee also observed a significant increase in DNA adducts in painters in comparison with controls (35). These toxic substances enter the body via the respiratory system and also the skin. As Chang proved (36), wearing respiratory masks reduces the concentrations of xylene and ethylbenzene to which painters are exposed by 96% and 94% respectively. In this study, and in the 2008 study, the proportion of xylene absorbed via the skin of ship painters is estimated at 63% (37). It is important to note that isocyanates, which cause severe occupational asthma (38), are less used in paints[jc4] .
Because of the processes they use, welders are exposed to gases such as carbon monoxide, which form carboxyhaemoglobin[jc5] , and also noxious and irritant gases such as nitrogen oxides and ozone. Phosgene (COCl2), aldehydes, and other products of decomposition such as phosphine, hydrogen cyanide, fluorine, or irritant gases such as acetyl chloride, can be emitted from grease residue or from chlorine-based solvents on areas that have been degreased, painted areas, resins, lubricants and paint strippers (3). On acute exposure, there is the risk of respiratory distress and welder’s fume fever. Welding fumes are classed as possible carcinogens by IARC, and the roles of hexavalent chromium and nickel in cancer have been discussed. These substances also cause chronic bronchial and lung disease. Chronic regular exposure (10-15 years) to iron dust carries a risk of siderosis (39). Because of the substitution programme, lead exposure, measured in 1992 as blood lead levels of 54.1 µg/dL (40) and mean 39 µg/dL in 59 welders (41), seems to be falling. Between 1991 and 2003, in a Baltimore shipyard, welders’ blood lead levels reduced by a factor of 2 (42). It has been shown that welders are exposed to nickel (43). Manganese poisoning, with its neuropsychological effects, is a disease that can affect welders (44). Same cases were found for aluminium in a population of 86 Italian shipyard welders (45). In this population, the risk of parkinsonism was studied recently. In 811 shipyard welders, a prevalence of 15.6% was found with a correlation between scale unit and exposure-years (46).
Work involving wood carried an excess risk of ethmoid sinus cancer and also of occupational asthma[jc6] (47). Further research is needed concerning the use of wood treatment products for lead paint, some of which, like pentachlorophenol, are toxic (1).
Workers can also be exposed to products or derivatives that are transported by ship, such as petroleum derivatives or carbon monoxide (48). We shall not go further into this aspect, which is less specific to shipbuilding and repair, and is also relevant to seamen.