Although there have been past releases and exposures, substantial controversy remains over the actual doses individuals received and the potential health effects at those doses. Given the uncertainties and the limitations of available data, ATSDR cannot reach a definitive conclusion about the health effects from past exposures to radioactive substances.

However, after reviewing historical air monitoring data and current literature ATSDR did conclude the following about past radioactive iodine (I-131) releases:

• Individuals who were at least 21 years of age during the I-131 releases were probably not exposed to harmful levels of radioactive iodines that would induce thyroid disease or cancer.

• Younger individuals (under the age of 18) were more sensitive to the potential adverse health effects associated with the uptake of radioactive iodines by the thyroid. Because of the wide range of potential exposures and the uncertainties associated with historical reconstruction of the dose estimates, ATSDR cannot identify specific population groups of younger individuals who may have been impacted by past releases from the site.

• Individuals who were under the age of 18 during the I-131 releases and who also received a thyroid dose in excess of 10 rads (0.1 Gy) should be considered the critical, sensitive population. ATSDR recommends continued health education to inform those who lived in the Hanford region during the period of the I-131 releases
• and their health care providers
• about the potential health risks of exposure to I-131.

The public health assessment is available to the public for review and comment, however, ATSDR will not be able to address comments or make this report final unless additional U.S. Department of Energy funds are received. Although we do not know when we will be able to address comments, we encourage members of the public to submit comments on our documents. Public comments are an essential part of public record.

Members of the community that have questions about the report may contact Senior Engineer Rita Tallini, Senior Health Physicist Michael Brooks, or Community Involvement Specialist Marilyn Palmer, toll free, at 1-800-CDC-INFO. Or, for more information about ATSDR activities at the Hanford Nuclear Site, visit http://www.atsdr.cdc.gov/hanford.

ATSDR, a federal public health agency of the U.S. Department of Health and Human Services, evaluates the human health effects of exposure to hazardous substances.