Just 3 days ago, the following press release made it into the news:
(http://www.vancouverobserver.com/news/first-nations-cancer-linked-oil-sands-toxinswild-
food-study)
Here is an excerpt condensed from the above article:
“Two northern Alberta First Nations downstream of massive oil sands smoke plumes and
tailing ponds released a human health study Monday, implicating the growth of the
industry to many serious Aboriginal health concerns, including cancer. The new
scientific study states the region’s “country food” contains elevated levels of toxic metals
and carcinogens that members of the Mikisew Cree and Athabasca Chipewyan First
Nations traditionally eat. The wild foods include: moose, ratroot, duck, wild mint, spruce
gum, pickerel, caribou, and Labrador tea. Fish are no longer eaten from the Athabasca
River, due to government health warnings. The study reveals these foods contained
elevated levels of heavy metals and carcinogens, and that nearly a quarter of the
Aboriginal participants — 23 out of 94 — had cancer, among other ailments.
The push for the study was motivated by a deep distrust of provincial and federal health
officials, who they say have “failed” to comprehensively study the issue, said the leaders.
“One thing most striking… is that both province and federal governments refuse to do
anything about [the high rates of cancer]. Even though the pressure is escalating,” said
ACFN Chief Allan Adam. “We are being brainwashed by the Conservative government
that everything is ok. It’s not,” he added.”
There are many interesting issues here – including the distrust of Alberta-based
researchers! — but we will focus here on hypotheses and study designs. Although I think
it’s great if you want to delve into this topic more deeply, you do not need to do any
further background research to answer the following questions. (We will be talking about
the tar sands a bit later in the course – stay tuned J).
Q1. Which of these two options is the better hypothesis statement and why? (2 marks)
A) Exposure to the tar sands causes cancer.
B) Exposure to tar-sand chemicals through the consumption of contaminated
wildlife increases the risk of developing certain cancers.
Q2. Suppose we decided to test the hypothesis: “Exposure to chemicals from the tar
sands via the consumption of contaminated fish increases the risk of developing
Summer 2014 – ENV1000 Assignment 1
6
cholangiocarcinoma (cancer of the bile duct)”. If this is the alternative hypothesis, what
would be the null hypothesis? (1 mark)
Q3. Suppose we decided to test the hypothesis: “Exposure to chemicals from the tar
sands via the consumption of contaminated fish increases the risk of developing
cholangiocarcinoma (cancer of the bile duct)”. What would be a reasonable prediction
arising from this hypothesis? (Remember that a handy way to develop a prediction is to
say “If the hypothesis is true, then…..” (2 marks)
Q4. Suppose that the following study designs have been proposed to test the
hypothesis “Exposure to chemicals from the tar sands through the consumption of
contaminated fish increases the risk of developing cholangiocarcinoma (cancer of the
bile duct)”. Very briefly critique each design: if you see a problem with it, say what you
think the problem is. If you think it is fine as is, say so. Please be brief! Possible
criticisms could be (but are not restricted to):
• not achievable
• unethical
• not measurable
• no control group
• results may not be reliable
• biased
• too small a sample
• does not test the hypothesis
• there may be other untested
variables affecting the outcome
If you see several problems, mention up to 2 problems for a complete answer.
4a. “I would measure the concentration of certain tar-sand contaminants in the blood of
a person with cancer and a person without cancer and see if they are different.” (1 mark)
4b. “I would interview 50 people living close to the tar sands who have this type of
cancer and ask them to estimate how much wild fish they consumed weekly over the last
5 years.” (1 mark)
4c. “I would interview 50 people living close to the tar sands who have this type of
cancer and ask them to estimate how much wild fish they consumed weekly over the last
5 years. Then, I would interview approximately the same number of people from
Toronto who DON’T have this cancer and ask them how much wild fish they consumed
weekly over the last 5 years and see if the amount of fish consumption differs between
the 2 groups.” (1 mark)
4d. “I would randomly assign 100 people to 2 groups. One group would eat
contaminated fish once a week for 5 years; the other group would eat uncontaminated
fish once a week for 5 years. I would see if the rate of cholangiocarcinoma differs
between the two groups.” (1 mark)
4e. “I would look at rates of cancer in the community and see if they started to rise after
the tar sands development came in (compared to before the tar sands were developed).”
(1 mark)
