Cancer incidence among residents of the Three Mile Island accident area: 1982-1995

Background

The Pennsylvania Department of Health established a registry of the Three Mile Island (TMI) nuclear power plant accident in 1979. Over 93% of the population present on the day of the accident within a 5-mile radius was enrolled and interviewed. We used the registry to investigate the potential cancer risk from low-dose radiation exposure among the TMI population.

Methods

Cancer incidence data among the TMI cohort were available from 1982 to 1995. Because more than 97% of the population were white and few cancer cases were reported for those younger than 18 years of age, we included whites of age 18 years and older (10,446 men and 11,048 women) for further analyses. Cox regression models were used to estimate the relative risk (RR) per 0.1 m Sv and 95% confident interval (CI) of cancer by radiation-related exposures. The cancers of interest were all malignant neoplasms, cancer of bronchus, trachea, and lung, cancer of lymphatic and hematopoietic tissues, leukemia, and female breast.

Results

Among men and women, there was no evidence of an increased risk for all malignant neoplasms among the TMI cohort exposed to higher maximum and likely γ radiation (RR=1.00, 95% CI=0.97, 1.01 and RR=0.99, 95% CI=0.94, 1.03, respectively) after adjusting for age, gender, education, smoking, and background radiation. Elevation in risk was noted for cancer of the bronchus, trachea, and lung in relation to higher background radiation exposure (RR=1.45, 95% CI=1.02–2.05 at 8.0–8.8 μR/h compared to 5.2–7.2 μR/h). An increased risk of leukemia was found among men exposed to higher maximum and likely γ radiation related to TMI exposure during the ten days following the accident (RR=1.15, 95% CI=1.04, 1.29 and RR=1.36, 95% CI=1.08, 1.71, respectively). This relationship was not found in women.

Conclusion

Increased cancer risks from low-level radiation exposure within the TMI cohort were small and mostly statistically non-significant. However, additional follow-up on this population is warranted, especially to explore the increased risk of leukemia found in men.