Residents and researchers explored the following questions to assess whether a health study was appropriate:
Yes. There was information about what chemicals were used, when the contamination occurred, and how much was emitted.
Yes. Researchers were able to estimate how the contaminants were released into the air and landed over the town. Based on this information, researchers assumed that people who went to school and lived near the facility had breathed the chemical.
Yes. Studies of people who were exposed to large amounts of this chemical in their workplace indicate that it can cause lung cancer. It may cause other cancers also, but this is less clear.
There had to be enough exposure to cause the specific health outcome that researchers were studying. Previous scientific studies of workers at other facilities where the same chemical was used showed increased rates of lung cancer. However, researchers believed that students probably had much less exposure to the chemical than workers at those other facilities. Unlike the workers, students did not directly handle the chemical. Students also spent less total time in school than the workers did at their jobs.
Researchers estimated the potential amount of exposure to the students. They determined that students were exposed to enough chemical to cause an increased risk of lung cancer. However, researchers anticipated that the increase in lung cancer cases due to the chemical would be much less in students than to workers.
The facility closed, ending emissions 10 years prior to the consideration of the health study. It usually takes over 10 years to develop lung cancer after the initial exposure. Cancers that occur before that time are not likely to be due to that exposure. Based on this information, the health study would identify lung cancer in some students, depending on when they attended school there.
See the section When is a health study appropriate? for explanations of the above questions.