State or local health departments will investigate the possibility of a cancer cluster when a claim is filed.
[3] In order to justify investigating such claims, health departments conduct a preliminary review.
At this point, a committee of medical professionals will examine the data and determine whether or not an investigation (often lengthy and expensive) is justified.
[4] In the U.S., state and local health departments respond to more than 1,000 inquiries about suspected cancer clusters each year.
It is a well-known problem in interpreting data that random cases of cancer can appear to form clumps that are misinterpreted as a cluster.