Shellfish in Port Gamble Bay

On Feb. 11, the Kitsap Sun ran a front page article with the headline “Health risks estimated for Port Gamble Bay shellfish,”  and a large sub-headline, “Port Gamble chemicals affect tribal members.”  Based on the headlines I expected the article to describe a real problem in Port Gamble Bay, but as I read on I began to feel the lead should have been something like, “Research fails to detect significant problem from pollution in Port Gamble shellfish.” 
To understand what I’m saying, let’s look at the numbers.  The article says a study has determined that out of every 1000 people who eat 1.1 lbs. of “clams, oysters, and crabs” from upper Port Gamble bay every day over a lifetime we can expect two to get a cancer caused by this consumption.  However, 1.1 lbs. is a lot of shellfish and the article goes on to say that only an estimated 5% of trial members would be expected to eat this amount.  I looked on the web for an estimate of the population of the S’Klallam tribe, and I believe 1000 members is a very generous estimate of tribal members living somewhere near upper Port Gamble bay (see Port Gamble Bay S’Klallam website: So we could expect that 5% of 1000, or 50 tribe members to be affected by the 2 cancers in 1000 people level of exposure.
Let’s assume an average lifespan is 70 years (remember, we’re talking about eating 1.1 lbs. of shellfish daily over a lifetime).  So, unless I’m doing the math incorrectly, the rate of cancer in the 50 people would be 2/1000 or .002 times 50 or 1 tenth of a cancer in the tribe each 70 years.  So we could expect 1 cancer caused by eating polluted shellfish in the Port Gamble S’Klallam each 700 years.  Based on a quick web search it appears that about half of cancers are now cured – using the most common definition of 5 year survival rates.  So we would expect one death each 1400 years if the current cure rate remains stable.  But of course it won’t, it will improve dramatically. 
I do not mean to be cavalier about environmental risks.  Certainly I don’t want anyone to get cancer but these levels of risk seem so small as to be essentially insignificant.  I wondered if I was missing something so I got a copy of the original Port Gamble shellfish report.  It has some interesting information. For example, it points out that the main source of pollution from shellfish in Puget Sound, including Port Gamble bay, is arsenic and a study of S’Klallam tribe members in 2001 found that their arsenic levels were within the normal range.  It also suggests that the level of risk posed by eating the shellfish could be offset by positive nutritional effects and benefits of the physical activity involved in shellfish collection. 
In my view, the Sun article will almost certainly mislead the average reader.  Most people will not read it carefully;  they will trust the headlines.  And they will not do any math.  So the unfortunate result will be that readers will be left with the impression that there is a major pollution problem in Port Gamble bay.  As far as I can tell, there is some pollution in the bay, but careful study shows it to be a very minor problem.  That should be the headline.
Carl Shipley

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