Thyroid cancer risks among medical radiation workers in South Korea, 1996-2015

Won Jin Lee, Dale L. Preston, Eun Shil Cha, Seulki Ko, Hyeyeun Lim

Research output: Contribution to journalArticle

Abstract

Background: Thyroid cancer rates, especially among children, are known to be increased by radiation exposure. However, little is known about the impact of chronic low-dose radiation exposure on thyroid cancer risk in adulthood. This study examined radiation effects on thyroid cancer rates as well as an overall evaluation of thyroid cancer risk among medical radiation workers. Methods: Data on all diagnostic medical radiation workers enrolled in the national dosimetry registry between 1996 and 2011 were linked with the cancer registry data through 2015. Standardized incidence ratios (SIRs) were used to compare the observed cancer incidence rates in this population to those for the general population while internal comparisons were used to estimate relative risks (RRs) for occupational history and excess relative risks (ERRs) were used to quantify the radiation dose-response relationship. Results: Overall, 827 thyroid cancer cases were reported among 93,922 medical radiation workers. Thyroid cancer SIRs were significantly higher than expected for both men (SIR 1.72, 95% confidence interval [CI] 1.53 to 1.91) and women (SIR 1.18, 95% CI 1.08 to 1.28). However, RRs for thyroid cancer by job title and duration of employment showed no particular pattern among diagnostic medical radiation workers. There were no indications of a significant dose effect on thyroid cancer rates for either men (ERR/100 mGy 0.07, 95% CI -0.38 to 0.53) or women (ERR/100 mGy -0.13, 95% CI -0.49 to 0.23). The findings were similar for different job titles or when limited to workers employed for at least one year. Conclusions: While thyroid cancer incidence rates among Korean medical radiation workers were somewhat higher than those in the general population, there was no significant evidence that this increase was associated with occupational radiation dose. Additional follow-up together with consideration of other risk factors should provide useful information on thyroid cancer rates in this cohort.

Original languageEnglish
Article number19
JournalEnvironmental Health: A Global Access Science Source
Volume18
Issue number1
DOIs
Publication statusPublished - 2019 Mar 11

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Republic of Korea
Thyroid Neoplasms
Radiation
Incidence
Confidence Intervals
Radiation Dose-Response Relationship
Registries
Population
Radiation Effects
Neoplasms

Keywords

  • Cohort
  • Neoplasm
  • Occupational exposure
  • Radiation
  • Thyroid gland
  • Workers

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

Cite this

Thyroid cancer risks among medical radiation workers in South Korea, 1996-2015. / Lee, Won Jin; Preston, Dale L.; Cha, Eun Shil; Ko, Seulki; Lim, Hyeyeun.

In: Environmental Health: A Global Access Science Source, Vol. 18, No. 1, 19, 11.03.2019.

Research output: Contribution to journalArticle

Lee, Won Jin ; Preston, Dale L. ; Cha, Eun Shil ; Ko, Seulki ; Lim, Hyeyeun. / Thyroid cancer risks among medical radiation workers in South Korea, 1996-2015. In: Environmental Health: A Global Access Science Source. 2019 ; Vol. 18, No. 1.
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abstract = "Background: Thyroid cancer rates, especially among children, are known to be increased by radiation exposure. However, little is known about the impact of chronic low-dose radiation exposure on thyroid cancer risk in adulthood. This study examined radiation effects on thyroid cancer rates as well as an overall evaluation of thyroid cancer risk among medical radiation workers. Methods: Data on all diagnostic medical radiation workers enrolled in the national dosimetry registry between 1996 and 2011 were linked with the cancer registry data through 2015. Standardized incidence ratios (SIRs) were used to compare the observed cancer incidence rates in this population to those for the general population while internal comparisons were used to estimate relative risks (RRs) for occupational history and excess relative risks (ERRs) were used to quantify the radiation dose-response relationship. Results: Overall, 827 thyroid cancer cases were reported among 93,922 medical radiation workers. Thyroid cancer SIRs were significantly higher than expected for both men (SIR 1.72, 95{\%} confidence interval [CI] 1.53 to 1.91) and women (SIR 1.18, 95{\%} CI 1.08 to 1.28). However, RRs for thyroid cancer by job title and duration of employment showed no particular pattern among diagnostic medical radiation workers. There were no indications of a significant dose effect on thyroid cancer rates for either men (ERR/100 mGy 0.07, 95{\%} CI -0.38 to 0.53) or women (ERR/100 mGy -0.13, 95{\%} CI -0.49 to 0.23). The findings were similar for different job titles or when limited to workers employed for at least one year. Conclusions: While thyroid cancer incidence rates among Korean medical radiation workers were somewhat higher than those in the general population, there was no significant evidence that this increase was associated with occupational radiation dose. Additional follow-up together with consideration of other risk factors should provide useful information on thyroid cancer rates in this cohort.",
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