Textbook of Maritime Medicine

Introduction

There are many chemical health hazards on board ships, especially on tankers and other ships with dangerous cargo. The exposures are often higher than on shore. Information and control of health hazards are often less developed on board than on shore. Exposure could lead to intoxication, asthma, or cancer. Engine room personnel could be exposed to carcinogenic substances, such as asbestos or polycyclic aromatic hydrocarbons from oils, soot, and engine exhaust. The deck crew on ferries could be exposed on car deck to engine exhaust, which could cause cancer or respiratory problems. Exposure to solvents, and irritating substances could also occur during painting and cleaning. Cleaning agents usually contain irritants or solvents, which could affect the nervous system, or alkaline substances, which could cause injuries to eyes, skin, and mucous membranes. Some of these exposures, especially high exposures to certain chemicals, could lead to acute poisoning. Other exposures are more insidious and could lead to chronic health effects, such as asthma, cancer or diseases of the nervous system. In the following, some of the most important exposures in seafaring, and their possible health effects, are reviewed.

11.2.1  Exposure to cargo vapours on tankers

Crude oil carriers are usually large or very large vessels. The voyages are usually long, and the loading and unloading operations are not so frequent. Crude oil constitutes a complex mixture of hydrocarbons, and other substances such as sulphur compounds. Acute intoxications with volatile hydrocarbons or hydrogen sulphide have been described, especially during loading and tank cleaning operations. The hydrocarbons affect mainly the nervous system and may cause dizziness and nausea, or after high exposure, unconsciousness. Hydrogen sulphide has an unpleasant odour in low concentrations and is highly poisonous as it blocks certain enzymes in the mitochondria, which could lead to unconsciousness or death at high exposures. In moderate concentrations it could cause irritation of the mucous membranes. In order to reduce the risk of explosion on crude oil carriers, washed engine exhausts are often used as an inert gas to fill the remaining void in the tank instead of air. Engine exhaust could have a comparatively high concentration of nitric oxides, which are mucosal irritants and could cause asthma.

Product tankers are usually smaller coastal tankers, which carry gasoline, diesel, or other refined petroleum products, and sometimes intermediate products from refineries. The content of benzene could be up to 5 % in gasoline, and even higher in some intermediate products. Product tankers often load and unload their cargo two to three times per week.

Chemical tankers are constructed to carry a large number of chemicals, some of which could be hazardous and poisonous, including isocyanates, which could cause asthma. The level of safety is usually higher on chemical tankers than on product tankers.

Exposures to cargo vapours on tankers are usually highest during loading, unloading and tank cleaning operations, but deck crew could also be exposed during work at the manifolder or in the pump room. The first mate is usually responsible for the cargo and the operations on deck. The exposure to e.g. hydrocarbons could be very high, especially during open loading (with the manholes or ullage holes open) when the concentrated cargo vapours are evacuated on deck. Manual gauging during top off (the last phase of the loading) used to be common on older tankers. The mate was often looking down through the manhole during the loading in order to be able to stop the loading when tank was full. The exposure at these occasions could be very high.

Nowadays, many ships use closed loading systems with automatic gauging of the cargo, but still the cargo gas has to be evacuated, usually through so called high jet vents. If there is no wind, the vapours could fall down on the deck, and also seek their way into the living quarters.

11.2.2  Possible health effects of exposure to petroleum vapours (hydrocarbons) on tankers

Volatile hydrocarbons from petroleum products, such as gasoline, kerosene or white spirit, could affect the central nervous system. Acute effects include symptoms such as fatigue, headache, nausea, dizziness, and, in severe cases, loss of consciousness. Very high or prolonged exposure (at least 5-10 years) could cause chronic toxic encephalopathy (CTE) with persistent symptoms such as asthenia, impaired memory, and concentration, and emotional disturbances. However, only few cases of CTE have been reported among seamen.

Seamen on tankers have an increased incidence of leukaemia, lymphoma, and multiple myeloma, possible due to exposure to benzene from gasoline, and other petroleum products. It is well known that benzene could cause leukaemia, especially acute myeloid leukaemia (AML). High exposure, above 50 ppm (parts per million) could cause leukopenia, and in rare cases aplastic anaemia. The occupational exposure limit (OEL) in most European countries is 0.5 ppm or 1.5 mg/m3 (8 h time-weighted average). The exact mechanism for the leukaemogenic effect is not known in detail, but several genotoxic substances are generated during the metabolism of benzene.

11.2.3  Benzene - toxicology and surveillance

The toxic effect of benzene depends on uptake, metabolism, excretion, and individual susceptibility. Personal sampling of benzene in air by e.g. dosimeters could detect hazardous exposure to benzene at an early stage. Benzene could also be detected in alveolar air, which reflects the benzene concentration in blood or by analysis of metabolised benzene or benzene metabolites, such as trans, trans-muconic acid or phenyl mercapturic acid in urine. Phenol in urine could also be used as biomarker if the exposure is high (above 20 ppm). Increased levels of biomarkers for cytogenetic and other genotoxic effects have also been described in research projects, but are at present stage not suitable to use for surveillance of individual exposure since the effects are mainly seen on group levels, and the results could be affected by other factors. Routine collection an analysis of white blood cell counts on persons occupationally exposed to benzene is not very sensitive and is not recommended.

11.2.4 Prevention of health effects from exposure to cargo vapours on tankers

The best primary prevention is by technical measures, such as installations of closed systems. In certain occasions effective personal protective equipment, such as facemasks, preferably with external air supply, could be used. Information and education of the crews are also very important. Routine test of blood, urine, and respiratory function are of limited value, but interviews and questionnaires about exposure and symptoms may reveal hazards, which could be prevented.

11.2.5  Other ships carrying dangerous cargo

Intoxications of seamen on mixed cargo ships transporting chemicals in bulk or in barrels have been described. It is important that the seamen have good information about the content of the cargo and of its possible health effect. They should be informed on the proper handling of the cargo, protective measures, and how accidental poisonings should be treated. Lung cancer and mesothelioma among seamen working on ships carrying asbestos have also been described.

11.2.6  Engine rooms

Engine room personnel have an increase incidence of lung cancer, partly due to exposure to asbestos, which also cause pleural cancer (mesothelioma). The engine room personnel could also be exposed to carcinogenic polycyclic aromatic hydrocarbons (PAH) or nitroarenes from bunker or lubricating oils, engine exhaust, and soot. The dermal uptake of PAH from oil on skin seem to be more important than exposure from air, and increased levels of biomarkers of exposure and genotoxic effects have been described. Carcinogenic PAH, such as benso-a-pyrene has been detected in heavy fuel oils, and in lower levels in marine diesel oil and in used lubricating oils.

11.2.7  Prevention of health hazards in engine room

It is important that the engine room crew have knowledge and are aware of the health  hazards, and use a good work practice, for instance by using nitrile gloves to prevent exposure of oils on the skin. Facemasks with a charcoal filter should be used when handling solvents, and protective glasses and gloves should be used when handling alkaline cleaning agents.

11.2.8  Chemical health hazards on car deck on ferries

The crew could be exposed to engine exhaust when working on the car deck, both from diesel engines, but the main exposure is nitric oxides, which could cause respiratory effects, and soot, which contain PAH. Gasoline engine exhaust contains carbon monoxide, which could cause headache, and other symptoms. It could also contain low levels of benzene. Good ventilation when starting the engines is important.

11.2.9 Painting

Paint may contain several hazardous substances, such as solvents (neurotoxic hydrocarbons), metals (lead oxide, which is neurotoxic), as well as irritating chemicals, such as isocyanates, which could cause asthma, and epoxy resins, which could cause allergic dermatitis. Instructions for the safe handling and protection, is  recommended.

11.2.10 Cleaning agents

These could either be solvent based or water based (alkaline). The solvent based usually contains hydrocarbons, which are neurotoxic. Chlorinated hydrocarbons, such as trichloretylene, are hepatotoxic and could cause cancer. The alkaline cleaning agents could cause serious eye injuries from splash, and protective glasses should be used when handling these substances. They could also cause irritation of the skin and respiratory mucosa. Information and knowledge of health hazards are important. Toxic substances should be replaced by less toxic substances and an appropriate personal protection should be used.