Textbook of Maritime Medicine

11.3.1   Introduction

Naval construction and repair have been industrial activities for many years. Ships have long been used by humans as a means of transport for goods or people, for discovery or invasion purposes. The distinction between the civilian and military aspects of these activities has often been made. Historically, the major centres for construction and repair have often been linked with military activity, and were developed in Europe, later in North America, and later still in south-east Asia and India. In 1998, the proportion of worldwide naval construction and repair taking place in South Korea, Japan and China rose above 80%. In Western Europe, the sector has one or two large players per country, and a multitude of small and medium-sized companies. In 1999, 182 firms in the EU had fewer than 1,000 employees, 17 had between 1,000 and 2,000 employees, and the 28 largest shipyards had a total of 64,000 workers[1].

Within this sector there are many career types, such as engineers, boilermakers, welders, pipefitters, ship painters, and each type of worker is exposed to multiple risks, mainly physical and chemical, and these will be described in this chapter.

11.3.2  An accident-prone sector

Naval construction, and particularly naval repair, have high rates of occupational accidents. Birgham noted (in 1983) a 35% accident rate for the state of Maine in the US (1). In France, in the largest civil repair yard, annual frequency rates ranging from 68 to 185 (with 10 years in which there were over 100 accidents) and seriousness ranging from 2.4 to 6.6 (with 7 years in which the score was above 4) were recorded in the period 1995-2008 (2). In terms of construction, published data from between 1997 and 1999 showed frequency rates of 57.8 to 66.5 and seriousness scores of between 0.65 and 0.87 in the Chantiers de l’Atlantique shipyards (3). It is interesting to compare these figures with the national figures for 2007, all jobs combined, for metallurgy and public building and works (which have accident frequency rates of 25.7, 24.8 and 53.03 respectively, and seriousness of 1.28, 1.05 and 2.76 respectively) (4). Shipbuilding and ship repair both have high rates of occupational accidents, more so than building and public works, but accidents are less serious overall in shipbuilding. Repair carries the highest risk of accidents and serious accidents.

Historical data from the UK show 8,939 recorded accidents, and an incidence of 7,010 accidents per 100,000 in 1974, with 19 fatal accidents in 1973 and 1975 (5).

In a study I carried out concerning 48 accidents involving ship repair workers, the most frequent part of the body affected by the accidents were hands, lower limbs and eyes, with the more serious accidents involving mainly hands and upper limbs. Most accidents (62.5%) occurred on board, and the rest in the workshop.

This fact can be explained by the ergonomic and organisational constraints (short deadlines) on board ships that are being repaired.

These data are taken from large shipyards; it is difficult to obtain data from small shipyards, which are a large part of the industrial fabric of boatbuilding.

11.3.3  Physical risks

As some work is carried out outside, workers are exposed to bad weather and changes in temperature. There are also heat sources (welding, grinding) that are used in poorly ventilated areas, which increases the temperature. There is little scientific data concerning risks in this population.

Noise exposure is one of the major occupational risks to which workers are exposed, particularly those involved in repair. The source of noise may be machines used as tools for cutting wood (120 dB peak noise) (1), or machine tools, impact (hammering, cutting and falling sheet metal), grinding and associated activities (engine room machinery, welding, and grinding in resonant spaces). In studies of workers in a shipyard, peak noise exposure was recorded as 135 dB from falling sheet metal, 111 dB for grinding, 117 dB for planing and hammering and exposure on an 8-hour watch of 93 dBA for a boilermaker and 94 dBA for a pipefitter. Ships’ energy requirements mean that their engines have to be maintained in port. Noise exposure ranges from 90 to 108 dB, as measured by Andro (6). The effects of such noise exposure on the hearing and on other parts of the body are addressed in another chapter of this textbook, written by Dr Jegaden, and I will therefore not explore this issue further (7, 8). The only thing to add is that for the population of workers that we are examining here, there is an aggravating factor. Many such workers are exposed to aromatic solvents such as toluene, xylene and styrene. It has been shown in the industry that these solvents are ototoxic and can, via cell toxicity, increase noise-linked hearing loss (9). The recent study by Triebig involving 248 shipyard workers who had been exposed to styrene showed that chronic intense exposure above regulatory limits (> 50 ppm) led to an increased risk of hearing loss (10).

Musculoskeletal problems, either acute or chronic, are frequent causes of time off work and declared occupational diseases in this population group. Use of vibrating tools (grinders, scurfers, turners) exposes workers to the risk of harm to the hands and upper limbs. In a study of 114 construction workers using tools vibrating at 6.32 and 13.39 m/s² respectively, mean use of 4.64 hours per day was investigated, and the period to onset of Raynaud’s disease was half as long as that given in the ISO 5349 PARK standard (11). This severe impact on the hands was confirmed by findings of reduced nerve conduction velocity in the wrist, hands and fingers in a population of workers in an American shipyard (12) and by the positive correlation between rates of vascular symptoms in the hand and the intensity of exposure to vibration via tools in 214 subjects (13). Tendinopathies in the shoulders (18% of welders in one shipyard) (14) and elbows are also linked to such exposure. Handling and staying in cramped positions for long periods are common in some types of welding and sheet metal jobs. A full welding kit can weigh over 30 kilos, and the nozzle can weigh 2.5 kilos. Electromyography tests on welders show heavy strain on the trapezium, deltoid and finger flexor muscles (15). Effects on the lumbar muscles have also been observed. The risk of lower back pain in welders working in shipyards was confirmed in the study by Axelopoulos concerning 853 workers in a shipyard (16). Over a year, 14% of workers took time off work because of lower back pain, and welders had the highest rate of absence at 18.3%. The recurrence rate reached 41% over the year, and was greater for those who had spinal disc herniation and reduced when working conditions were altered (in favour of workshop work or limiting handling). This confirmed the considerable ergonomic constraints to which workers on board ships are subjected, particularly welders, pipefitters and sheet metal workers. For engineers, the most risky aspects of work is handling, with equipment weighing tens or over a hundred kilos (stern post) that must be manipulated within confined spaces and with little leverage assistance, apart from hoists.

As Brigham (1985) pointed out in his article concerning health in shipbuilding and repair, the risk of ophthalmological disease is the dominant risk (1). These can be divided into two main categories: foreign bodies in the eye, and diseases related to UV and IR exposure. Grinding work is primarily responsible for exposure to the risk of foreign bodies in the eye. Acute corneal lesions, keratitis and secondary effects in the form of traumatic cataracts and ocular siderosis can arise as a result of foreign body exposure (17). Such accidents represented 27% of all occupational accidents in ship repair in 2007, and 18.8% in 2008 (2).  Welding is the main activity that causes UV exposure, with the risk of arc eye and ocular melanoma (18) and keratoconjunctivitis photoelectrica, known as “arc eye” (19).

11.3.4  Chemical risks

This part of the chapter is, in my view, very important. As we shall see, workers in shipyards have been, and still are, exposed to toxic substances, some of which are carcinogenic and have sadly 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. We should not try to hide the fact that 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 by the IARC.

Another concern in terms of prevention of chemical risk is high levels of exposure to hydrocarbons in various firms. Aromatic hydrocarbons are found in solvents, that currently contain toluene and xylene (43% of workers exposed, NIOSH 1982) and these are widely used by engineers and painters, and styrene, which is used in boatbuilding(1). These are central nervous system depressants, and carry a long-term risk of diseases such as psycho-organic syndrome. 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 (26, 27). Exposure to carcinogens such as benzene (a leukemogen) and trichloroethylene (which causes kidney cancer) also occurred before these substances were banned (28). Occupational exposure can be direct (use of a product) or indirect, via the products being transported (petroleum derivatives). The same is true for oil products, with increased occurrence of lung and skin cancer found in those working on board tankers (29).

Styrene is used in the polymerisation of polyester resins, and represents 40% of the weight of these resins (1). It is classed as 2B 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[2] and glycol ethers, which were 4 times higher than for painters working on deck (30). Ethylene glycol acetates carry a risk of haematological disorders such as bone marrow depression (30). 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, which is a definite carcinogen according to the IARC, until the 1990s. 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. There is little human toxicology data on these substances, apart from one which showed respiratory sensitivity to chlorothalonil (31). 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 (32), 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 (33). 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 Bitulatex paint and crystalline silica, which carries a risk of pneumoconiosis and bronchial and lung cancer. 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 (34). These toxic substances enter the body via the respiratory system and also the skin. As Chang proved (35), wearing respiratory masks reduces the concentrations of xylene and ethylbenzine 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% (36). It is important to note that isocyanates, which cause severe occupational asthma (37), are no longer used in paints.

Because of the processes they use, welders are exposed to gases such as carbon monoxide, which form methaemoglobin, and also noxious and irritant gases such as nitrogen oxides and ozone. Phosgene (COCl2), aldehydes, and other products of decomposition such as phosphene, 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 (38). Because of the substitution programme, lead exposure, measured in 1992 as blood lead levels of 54.1 µg/dL (39) and mean 39 µg/dL in 59 welders (40), seems to be falling. Between 1991 and 2003, in a Baltimore shipyard, welders’ blood lead levels reduced by a factor of 2 (41). It has been shown that welders are exposed to nickel (42). Manganese poisoning, with its neuropsychological effects, is a disease that can affect welders (43).

Work involving wood carried an excess risk of ethmoid sinus cancer and also of occupational asthma (44). Further research is needed concerning use of 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 (45). We shall not go further into this aspect, which seems to be less specific to shipbuilding and repair, and is also relevant to seamen.

 11.3.5 Conclusion

This sector has a high rate of accidents, and workers in this sector are exposed to multiple risks. Some of these risks are increased because of the nature of work in an environment built to improve maritime and economic capacity, rather than to be appropriate for people to work in. These companies should prioritise changes to working practices and protection for individuals. We are also faced with difficulties in raising awareness and implementing preventative measures among these population groups, and it is essential that information about occupational risks be made available. In this chapter, we have looked at a selection of the various occupational risks, particularly chemical risks, which are examined in greater depth in other chapters of this textbook.

References

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[1] The Shipbuilding and Ship repair sectors in the candidate countries : Poland, Estonia, the Czech Republic, Hungary and Slovenia. Final Report PSE/99/502333.

[2] Translator’s note: the French here says “methyl ethyl ketone”, but reference 30 mentions methyl isobutyl ketone