22 Jul Does Pictou have higher cancer rates?

On Saturday, I questioned Herald columnist Gail Lethbridge’s contention that Pictou County has some of Canada’s highest cancer rates, and these may be attributable to noisome emissions from the Northern Pulp mill. Among other things, I faulted Lethbridge for not citing a source for her claims about cancer rates in Pictou, for not indicating which of the 200+ cancers are higher there, and for drawing conclusions about public health based on anecdotal evidence.

A Contrarian reader who worked at the “Cancer Lodge in Halifax” (which I take to mean the Canadian Cancer Society’s Daffodil Place) takes up the cause:

Many patients staying at the Lodge discussed how the number of cancer patients from the Pictou/Trenton area were higher than any other area in Nova Scotia. Out of sheer curiosity, I checked this out in the data files which I had access to, and lo and behold they were absolutely right. That area was far and away higher than any other area of Nova Scotia as far as cancer rates were concerned.

Well, maybe. Here are some factors I would want to consider before concluding that cancer rates are higher in Pictou County, let alone attributing those cancers to the Northern Pulp mill, obnoxious as it is:

Does the Daffodil Lodge reflect the whole province? It provides “home-away-from-home” support for patients who travel to Halifax for cancer treatment. That eliminates patients from Metro, and those patients from surrounding counties who stay in their own homes during treatment. It eliminates most patients from Cape Breton, which has a cancer treatment centre of its own. Taken together, that’s well over half the province absent from the sample.

Does a confirmation bias kick in when “many patients discuss” the disproportionate number of Pictou-area residents at the lodge? Confirmations bias is our natural tendency to notice data that confirms a theory we’re considering, while overlooking conflicting data.

What demographic factors might be at play in Pictou County cancer rates? The Canadian Cancer Society cites Nova Scotia’s aging population as a “key factor” in cancer rates here.

Which of the 200+ types of cancer are patients at the Lodge being treated for? During the late 20th century, Industrial Cape Breton experienced high rates of cervical cancer. Some people tried to blame this on the Sydney Steel Plant, the Coke Ovens, or the Tar Ponds. But cervical cancer is a sexually transmitted disease, caused by human papilloma viruses (HPVs), with no indication of an environmental component, so the alleged industrial link didn’t stand up.

What confounding factors might contribute to high cancer rates in Pictou County? What are the rates of poverty and unemployment, both strongly correlated with ill health? What are smoking rates in the county? What other industries operate there?

What proportion of Pictou’s cancer patients work at the Northern Pulp mill? If noxious emissions are implicated in the cancer rates, plant workers would be the most susceptible, because their exposure to the fumes would be orders of magnitude higher than residents of the county in general.

The Northern Pulp mill has a disgusting history, and it continues to spread environmental blight in the air, water, and land around the plant. The province has been, by times, a co-conspirator in this blight and a feckless regulator. I would be happy to see the mill close, and the mess it created cleaned up.

But I think public health decisions should be based on evidence, not speculation.