Gofman used his low-level radiation health model to predict 333 excess cancer or leukemia deaths from the 1979 Three Mile Island accident. Studies of the health effects of the Three Mile Island accident have so far (by 2013) not observed any excess mortality. A retrospective study of Pennsylvania Cancer Registry found an increased incidence of thyroid cancer in counties south of TMI and in high-risk age groups. The Talbott lab at the University of Pittsburgh reported finding only a few, small, mostly statistically non-significant, increased cancer risks within the TMI population. However, excess leukemia among males was observed. The ongoing TMI epidemiological research has been accompanied by a discussion of epidemiological methodology, such as problems in dose and illness classifications.