Chemical contamination of potable water in ship tanks

Unpleasant odour from drinking water in newly built ships is increasingly documented by the German Port Health Authority during sanitary inspections. Chemical contaminations are assumed to originate from washed off solvents of tank coatings due to the non-maintenance of required drying periods. The aim of this study was to explore the frequency of drinking water contamination by chemicals in a selected sample of vessels and to assess the usefulness of recommended control measures.

The available analyses of chemicals in drinking water from container ships which were taken by the Port Health Officers of the Hamburg Port Health Center in the last three years were summarized and analysed. Each analysis was initiated due to aromatic odour. The analysis spectrum comprised 22 different volatile halogenated hydrocarbons and solvents.

Drinking water analyses of 21 container ships with a maximal age of one year were available. The guideline value (GV) of chemical substances in drinking water was exceeded on five different ships (23.8 %) (ship no 1: xylene 770 microg/l (GV 500 microg/l), ethyl benzene 590 microg/l (GV 300 microg/l), vinyl chloride 0.6 microg/l (GV 0.5 microg/l); ship no 2: xylene 510 microg/l, ethyl benzene 400 microg/l; ship no 3: xylene 860 microg/l; ship no 4: xylene 540 microg/l; ship no 5: benzene 1.0 microg/l (GV 1.0 microg/l)). In 70% of ships with follow-up analyses, the chemical concentrations in potable water decreased as consequence of appropriate intervention measures (complete discharge and ventilation of the tanks for at least 14 days).

The study shows that an aromatic odour on newly built ships indicates a potential hazard to human health due to chemical solvents. In order to control possible adverse health effects to seafarer suitable codes of practice in the handling of coatings need to be observed by manufacturers. Public Health Officers, ship masters and other persons responsible for health and safety on board have to be aware of the problem and to initiate surveillance and control measures. Recommended measures include the complete emptying of potable water tanks, the accelerated drying of tank coatings by means of ventilators for at least 14-21 days and the thorough cleaning of tanks with acetic acid.