Yarnall, Hughes, Turnbull & Michaud (2012)

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Evaluating the effectiveness of the US Navy and Marine Corps Tobacco Policy: an assessment of secondhand smoke exposure in US Navy submariners is a self explanatory title, which presupposes the result regardless of the evidence, or methods in collecting that evidence. Or that there is indeed a problem to begin with.



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.

As expressed elsewhere on this site, SHS harm to others is negligible to non-existent, and the use of cotinine as a marker for consumption of nicotine (especially with regard to SHS) is rendered useless in the presence of other sources of cotinine such as food.


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

Again, the (mis-)use of cotinine as a marker for nicotine via tobacco when it can come from other sources. Note that none of the smokers were asked to participate.


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.

So, someone is in the presence of SHS (or eats tomatoes) and has what we shall call an 'elevated level' of cotinine present in their system.

Remove the SHS and the amount of cotinine, while still present (cotinine has a half-life of 20 hours, and is - in the absence of further sources - undetectable after a week[1]) merely halves to a 'base level.'

Either the 'base level' is too dangerous, or the 'elevated level' isn't. If the former, then something is severely wrong with people. If the latter, it makes a nonsense of this research.

Chris Snowdon Expands on this 2.1 times figure:

To be precise—for the devil is in the detail here—the average background level of urinary cotinine [in the submariners] was 0.33 ng/ml and the average level found once in the submarine was 0.69 ng/ml. That is a doubling. No doubt about it. But is it of any clinical significance? Let's look at what typical urinary cotinine levels are in smokers and nonsmokers.

Wall (1988) found a level of 6.0 ng/ml in unexposed nonsmokers, rising to 9.2 ng/ml for 'exposed' nonsmokers. Thompson (1990) found a level of 4.4 ng/ml in nonsmokers who lived with nonsmokers and a level of 11.4 ng/ml for those who lived with smokers. Repace (2005) found levels of around 3 ng/ml for nonsmokers, rising to around 8 ng/ml after 6 hours in a smoky bar.

All these figure are considerably higher than both the 'unexposed' and 'exposed' members of submarine crews today, presumably because the background level of smoke exposure has fallen sharply in the last 25 years due to smoking bans and the decline in the number of smokers. Levels of urinary cotinine in 'exposed' submarine crew are a fraction of those found in 'unexposed'—and therefore, by implication, 'safe'—nonsmokers a few years ago.

But it is only when we compare these levels with those found in smokers that we really see the figures in context. Wall (1988) found levels of 646.8 ng/ml in smokers of 10 or fewer cigarettes per day. For heavier smokers, the level was 1,100.7 ng/ml. Thompson (1990) found an average level of 1,623 ng/ml in smokers. Holl found an average level of 2,671 ng/ml.[2]


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.



  1. Cotinine - Wikipedia
  2. Smoke and submarines] - Velvet Glove, Iron Fist blog