Most of the people afflicted with new cases of the disease had regularly drunk larger quantities of Harborville's water than had other Harborville residents.

The same type of pollutants that were found in Harborville's water have independently been linked to occurrences in other towns of high rates of the disease.

Some of the people with newly diagnosed cases of the disease began to develop the disease before Harborville's water became polluted.

The rate of new cases of the disease among residents of Harborville who get their water from private sources is not unusually high.

Towns with geographic and demographic characteristics similar to those of Harborville but without polluted water do not have as high a rate of the disease as does Harborville.