Research

Dr. Zablotska has developed her own research niche in radiation cancer epidemiology by combining traditional epidemiological methods with molecular and genetic methods. Her current research interests could be described as follows:

Risks of occupational radiation exposures

Beginning with her doctoral dissertation work, one of the main themes of her research has been an examination of risks of occupational exposures to ionizing irradiation. Although the atomic bomb survivors study has provided much of what we know about the effects of gamma radiation, several questions remain unresolved. Her work on the studies of Canadian and U.S. nuclear workers has provided the missing link with regards to the effects of low-dose radiation exposures. In recent years, she has been working on developing a new area of research on the risks of occupational exposures among workers of the uranium fuel production cycle exposed to a wide range of uranium compounds from the ore dust and to other radioactive and non-radioactive mill products. Her studies add to an emerging consensus that radiation risks for workers employed in uranium processing are substantially different from risks of uranium miners or uranium enrichment workers or nuclear workers. In addition to conducting several studies of occupationally exposed workers in the U.S. and Canada, Dr. Zablotska is currently conducting pooled analyses with several European cohorts and actively participating in international consortia pooling the data from individual worker studies.

Risks of thyroid cancer and other thyroid diseases after exposures to radioactive iodines from the Chornobyl nuclear accident fallout

In collaboration with intramural scientists from the Radiation Epidemiology Branch at the NCI and a multidisciplinary team of scientists from Columbia University, Dr. Zablotska has been involved in several studies of those exposed to radiation after the Chornobyl nuclear accident in 1986. Initially as an epidemiologist and later on as a PI of the Columbia subcontract, she was specifically instrumental in the recruitment of two large cohort studies of ~25,000 subjects in Ukraine and Belarus and for biennial screenings for thyroid diseases starting in 1997. The studies were first to show that exposures to ingested and inhaled radioactive iodines lead to increased risks of thyroid cancer similar to risks from external radiation. Study findings raised concerns about radioiodines and redefined the emergency protocols for populations working or living around nuclear power plants. This work was instrumental in preventing large-scale consequences for the population living around the Fukushima plant in Japan. Dr. Zablotska has participated in the international effort to establish follow-up studies of those affected by the Fukushima. Her research also opened a new area of inquiry by showing that exposures to radioiodines increase not only the risks of thyroid cancer, but also of benign thyroid tumors such as follicular adenomas.

Radiogenicity of chronic lymphocytic leukemia (CLL)

Dr. Zablotska’s recent work on the risks of leukemia in Chernobyl cleanup workers addressed a long-standing controversy regarding differences in risks for CLL and non-CLL leukemia. Previous studies, including the study of atomic bomb survivors, showed no increased risks of CLL mortality after radiation exposures. In collaboration with colleagues, they demonstrated that mortality studies are unsuitable for the study of CLL due to its benign course and significant underreporting on death certificates. The group was the first to provide unequivocal evidence of significantly increased radiation-related risks of incident CLL. Their findings were confirmed in the most recent incidence follow-up of atomic bomb survivors and in several recently published incidence-based studies of occupationally exposed workers. For the past ten years, Dr. Zablotska has served as a scientific adviser on several NIOSH committees on CLL radiogenicity. The emergence of CLL as a radiation-induced disease has prompted NIOSH to reconsider the radiogenicity of CLL and its eligibility for compensation for U.S. nuclear weapons workers occupationally exposed to radiation. Starting in 2013, CLL is designated as a “covered condition” because of the high probability of causation by ionizing radiation similar to all other types of leukemia. This group continues work in this area by examining risks of CLL from low-dose radiation exposures in other populations, including uranium workers and the general population from the InterLymph Consortium of population-based lymphoma studies.

Cancer and non-cancer risks after diagnostic and therapeutic medical radiation exposures

Many of Dr. Zablotska’s publications have dealt with understanding the effects of radiation exposures in medical settings. In several studies using the SEER data, she used novel statistical analysis methods to show that breast cancer patients who received radiotherapy after mastectomy for breast cancer were at increased risk of second primary cancers such as lung and esophageal cancer. These findings spurred a new area of research and have been widely cited by subsequent larger observational studies and clinical trials. More recently, she reported that therapeutic and repeated diagnostic radiation exposures lead to excess mortality and morbidity from circulatory diseases. This work was instrumental in the development of a grant to examine risks of repeated X-ray fluoroscopies in a unique cohort of 64,000 Canadian tuberculosis patients with detailed exposure and confounder data which was funded in February 2016. The study seeks to provide evidence on the effects of low-dose protracted radiation exposures similar to exposures from computed tomography.

Clinical Epidemiology

As an epidemiologist with extensive training in advanced biostatistics, Dr. Zablotska has been involved in several studies examining the effects of environmental exposures, diet and gene-environment interactions on the risk of cancer. In collaboration with colleagues from the UCSF Department of Obstetrics and Gynecology, they have recently developed a new epidemiological cohort of almost 4,000 pregnancies to address critical public health questions regarding potential metabolic risk to children conceived through fertility treatments. This information will inform parents and guide clinicians and scientists in developing new technologies that improve treatment outcome and decrease risk to children.