Objective: According to the Norwegian Road Traffic Act, car drivers are not allowed to operate a vehicle with a blood alcohol concentration (BAC) above 0.2 g/kg. Depending on the size of the boat or ship, boat drivers/captains/first mates are not allowed to conduct the boat with a BAC above 0.8 g/kg when driving small boats (length less than 15 m) and above 1.5 g/kg when running larger vessels/ships. The new Sea Act of June 2005 states that captains/first mates cannot conduct a ship if he/she has a BAC above 0.2 g/kg. Our aim was to determine the current median BAC in a large population of car and boat drivers in Norway. Our other aim was to study if median BAC was higher in boat drivers than in car drivers who were suspected by the police to be impaired. Furthermore, we wanted to investigate if the BAC levels were differently distributed by gender or age within and between these two groups.
Methods: The Norwegian Institute of Public Health analyzes blood samples from all car/boat drivers suspected of driving under the influence of alcohol and non-alcoholic drugs. In the present study, samples submitted between 01.05 and 01.09 in 2002-2004 were included. Drivers, who in addition tested positive for drugs or abuse substances other than ethanol were excluded.
Results: There were 321 boat drivers and 3,061 car drivers who were suspected to be under the influence of ethanol only. The median BAC in boat drivers (1.76 g/kg [range 0.02-3.54]) was significantly higher compared to that in car drivers (1.54 g/kg [range 0.00-4.27]). In the car driver group, the mean BAC did not differ significantly between men and women. The median level of BAC was significantly higher in men than in women in the boat driver group (1.77 g/kg with CI 1.69-1.85 vs. 1.27 g/kg with CI 0.78-1.76).
Conclusions: Alcohol impairment of car drivers is known to be considered the most important contributing cause of car crash injuries. Driving a boat may demand the same degree of performance skills as driving a car. The median BAC in apprehended boat drivers was considerably high in the present study. The median BAC was also high in car drivers despite strict legislation. The population of drivers of cars in our study, however, is from previous studies known to contain a large proportion of heavy drinkers. Less is known about the drinking habits in boat drivers, and caution is needed in generalizing from our results. However, our results indicate the possible need for stricter legislation and more frequent police control that will hopefully prevent serious accidents caused by ethanol drinking at sea.