The apparent discrepancy in Dr. Bronstein's statements revolves around two points:
He attributes an increase in cancer-related mortality largely to lung cancer, which is largely due to smoking.
He agrees with estimates that approximately 80 percent of human cancers are caused by environmental factors, not by smoking.
To reconcile these points, we need to consider how these two statements can coexist without contradiction.
Explanation of Options:
a) The sources which Dr. Bronstein cited for the statistics linking 80 percent of human cancers to environmental factors cited smoking as the next largest cause of human cancers.
This option does not directly address the discrepancy. It merely adds information about the relative importance of smoking compared to other environmental factors.
b) Dr. Bronstein fails to make the assumption that a given cancer could not be attributable to more than a single cause.
This option suggests that cancers could have multiple causes, but it doesn't directly explain how the 80 percent figure and the role of smoking can be reconciled.
c) Many of the cancers caused by environmental factors do not result in death.
This option does not address the core issue, which is the attribution of cancer causation rather than the outcome (death) of those cancers.
d) It is possible for the results of even the most methodologically sound of studies to be proven wrong at a later date.
This option introduces the possibility of error in studies but does not explain the specific discrepancy in Dr. Bronstein's statements.
e) Dr. Bronstein fails to consider that many of the individuals whose cancers were environmentally caused may have also been smokers.
This option directly addresses the discrepancy. It suggests that environmental factors and smoking are not mutually exclusive. Many individuals could have cancers caused by a combination of environmental factors and smoking. Thus, smoking can be a significant contributor to lung cancer mortality while still fitting within the broader context of environmental factors causing a large percentage of cancers.
Therefore, the option that most contributes to explaining the apparent discrepancy is:
(e)