Objective To evaluate the effectiveness of the US Navy and Marine Corps tobacco policy in protecting submariners from secondhand smoke (SHS) by determining if non-tobacco users experienced a significant increase in urinary cotinine levels at sea when compared with in port levels.

Methods From February to August 2009, 634 volunteers recruited from nine US Navy submarines completed a survey to collect demographic data, information on tobacco use and pre-deployment exposure to SHS. Non-tobacco users (n=239) were requested to provide two urine samples (pre-deployment and while at sea) to quantify exposure to SHS using urinary cotinine as a biomarker. Matched samples were analysed using liquid chromatography–tandem mass spectrometry.

Results Overall, deployed cotinine levels were 2.1 times the in port levels in non-tobacco using submariners (95% CI 1.8 to 2.4, p<0.001, n=197). A significant increase in deployed urinary cotinine levels was found aboard six of nine submarines (p<0.05). A subgroup of submariners (n=91) who reported no SHS exposure within 10 days prior to in port cotinine sampling had deployed cotinine levels 2.7 times the in port levels (95% CI 2.2 to 3.3, p<0.001). Applying a 4.5:1 urine cotinine to serum cotinine correction factor, submariners' deployed geometric means are similar to recent US male population values at the 75th percentile.

Conclusions This study provides evidence that non-tobacco using submariners were exposed to SHS. Exposure was seen in all submarine classes and was not limited to personnel working in proximity to the smoking area. The existing policy was inadequate to protect non-smokers from exposure to SHS and required revision. As a result of a policy review, informed by this study, smoking below decks was banned aboard all US Navy submarines effective 31 December 2010.