Deck 30: Chemical Signaling Within the Animal Body

Question 1

How Strong Is the Association Between Smoking and Lung Cancer?
About a third of all cases of cancer in the United States are directly attributable to cigarette smoking. The association between smoking and cancer is particularly striking for lung cancer. The lung you see in the photograph below, riddled with cancer, is that of a smoker. A cancerous tumor has almost completely taken over the top half, and the black discoloration is due to tars. Cancer cells can migrate from the lungs into the lymph and blood vessels, and spread through the body. Many victims of lung cancer die of secondary tumors that form in other parts of the body, such as the brain. Over half a million people will die of cancer in the United States in 2015; about 27% of them will die of lung cancer.
All Americans die. The tragedy of this statistic is that so many die unnecessarily soon-fully 87% of the lung cancer deaths were cigarette smokers. Smoking is a popular pastime among Americans. In the United States, 18% of adults and 14% of teens smoked in 2012. The smoke emitted from these cigarettes contains some 3,000 chemical components, including vinyl chloride, benzo[ a ]pyrenes, and N-nitrosonornicotine, all potent mutagens. Smoking places these mutagens into direct contact with the tissues of the lungs, with cancer as the potential result.
How strong is the correlation between the number of cigarettes smoked per day and the incidence of lung cancer? To find out, a detailed study was made of the incidence of lung cancer among American men and of the cigarettes smoked per day. The results are presented in the graph above.
Applying Concepts The vertical lines drawn through the points on the graph are "error bars." How much estimation error is associated with the estimate of cancer incidence among men smoking 20 cigarettes a day? 30 cigarettes?

Answer 1

The "incidence of cancers per 100,000 men" plotted on Y axis is a dependent variable. The incidence of lung cancer is the variable not being manipulated in the experiment. The estimation error for 20 cigarettes per day is about 80 per 100,000 men. The estimation error for 30 cigarettes per day is about 175 per 100,000 men.

Question 2

How Strong Is the Association Between Smoking and Lung Cancer?
About a third of all cases of cancer in the United States are directly attributable to cigarette smoking. The association between smoking and cancer is particularly striking for lung cancer. The lung you see in the photograph below, riddled with cancer, is that of a smoker. A cancerous tumor has almost completely taken over the top half, and the black discoloration is due to tars. Cancer cells can migrate from the lungs into the lymph and blood vessels, and spread through the body. Many victims of lung cancer die of secondary tumors that form in other parts of the body, such as the brain. Over half a million people will die of cancer in the United States in 2015; about 27% of them will die of lung cancer.
All Americans die. The tragedy of this statistic is that so many die unnecessarily soon-fully 87% of the lung cancer deaths were cigarette smokers. Smoking is a popular pastime among Americans. In the United States, 18% of adults and 14% of teens smoked in 2012. The smoke emitted from these cigarettes contains some 3,000 chemical components, including vinyl chloride, benzo[ a ]pyrenes, and N-nitrosonornicotine, all potent mutagens. Smoking places these mutagens into direct contact with the tissues of the lungs, with cancer as the potential result.
How strong is the correlation between the number of cigarettes smoked per day and the incidence of lung cancer? To find out, a detailed study was made of the incidence of lung cancer among American men and of the cigarettes smoked per day. The results are presented in the graph above.
Interpreting Data
a. If the incidence of cancer per 100,000 men is 100, what is the percent of men with cancer?
b. Do you see a trend in the magnitude of the error bars in the graph? What might account for this?

Answer 2

If the incidence of cancer per 100,000 men is 100, the percent of men with cancer is 0.1%.
Yes, there is a trend in the magnitude of the error bars in the graph. As the number of cigarettes per day increases, the estimation error bars get larger. This suggests that there is much more variation in the incidence of lung cancer in people who smoke more cigarettes. This is because some people are more susceptible to lung cancer than others.

Question 3

How Strong Is the Association Between Smoking and Lung Cancer?
About a third of all cases of cancer in the United States are directly attributable to cigarette smoking. The association between smoking and cancer is particularly striking for lung cancer. The lung you see in the photograph below, riddled with cancer, is that of a smoker. A cancerous tumor has almost completely taken over the top half, and the black discoloration is due to tars. Cancer cells can migrate from the lungs into the lymph and blood vessels, and spread through the body. Many victims of lung cancer die of secondary tumors that form in other parts of the body, such as the brain. Over half a million people will die of cancer in the United States in 2015; about 27% of them will die of lung cancer.
All Americans die. The tragedy of this statistic is that so many die unnecessarily soon-fully 87% of the lung cancer deaths were cigarette smokers. Smoking is a popular pastime among Americans. In the United States, 18% of adults and 14% of teens smoked in 2012. The smoke emitted from these cigarettes contains some 3,000 chemical components, including vinyl chloride, benzo[ a ]pyrenes, and N-nitrosonornicotine, all potent mutagens. Smoking places these mutagens into direct contact with the tissues of the lungs, with cancer as the potential result.
How strong is the correlation between the number of cigarettes smoked per day and the incidence of lung cancer? To find out, a detailed study was made of the incidence of lung cancer among American men and of the cigarettes smoked per day. The results are presented in the graph above.
Making Inferences
a. There are 20 cigarettes in a pack. What is the incidence of cancer among "a-pack-a-day" smokers?
b. What is the incidence of lung cancer among nonsmokers?
c. Compare the risk of contracting lung cancer among individuals who smoke one pack a day to the risk among nonsmokers.
d. Is the relationship between cigarettes smoked per day and incidence of lung cancer linear? Why do you think the relationship is this way? What do you think this says about the risks of heavier smoking?

Answer 3

The incidence of lung cancer among "a pack a day" smokers is 150 men per 100,000.
According to the graph, the incidence of lung cancer in nonsmoking men (0 cigarettes per day) is less than 5 per 100,000.
A pack a day smoker is 30 times more likely to be diagnosed with lung cancer compared to a nonsmoker.
No, the relationship between cigarettes smoked per day and the incidence of lung cancer is not linear. A line drew through the points, curves with a higher incidence of cancer occurring, as more cigarettes are smoked per day. This suggests that the more cigarettes a man smokes, the higher the risk of him getting lung cancer.

Question 4

How Strong Is the Association Between Smoking and Lung Cancer?
About a third of all cases of cancer in the United States are directly attributable to cigarette smoking. The association between smoking and cancer is particularly striking for lung cancer. The lung you see in the photograph below, riddled with cancer, is that of a smoker. A cancerous tumor has almost completely taken over the top half, and the black discoloration is due to tars. Cancer cells can migrate from the lungs into the lymph and blood vessels, and spread through the body. Many victims of lung cancer die of secondary tumors that form in other parts of the body, such as the brain. Over half a million people will die of cancer in the United States in 2015; about 27% of them will die of lung cancer.
All Americans die. The tragedy of this statistic is that so many die unnecessarily soon-fully 87% of the lung cancer deaths were cigarette smokers. Smoking is a popular pastime among Americans. In the United States, 18% of adults and 14% of teens smoked in 2012. The smoke emitted from these cigarettes contains some 3,000 chemical components, including vinyl chloride, benzo[ a ]pyrenes, and N-nitrosonornicotine, all potent mutagens. Smoking places these mutagens into direct contact with the tissues of the lungs, with cancer as the potential result.
How strong is the correlation between the number of cigarettes smoked per day and the incidence of lung cancer? To find out, a detailed study was made of the incidence of lung cancer among American men and of the cigarettes smoked per day. The results are presented in the graph above.
Drawing Conclusions Do these results support the hypothesis that cigarette smoking causes cancer? Do they prove it? Explain.