According to a 2012 report of the Nuclear Safety and Security Commission, 5606 workplaces handle radiation-generating devices and radioactive isotopes in Korea, and the number of workers in radiation-related jobs has been estimated to be 42,226, which is increasing every year, with interest in radiation-related health problems simultaneously increasing [1].The radiation at these workplaces influences the health and safety of workers, causing various conditions, such as cancer and genetic and hereditary effects [2, 3]. Radiation exposure can also possibly cause male infertility, which is the failure to achieve pregnancy after 12 months of intercourse [4] and is known to result from combined abnormalities in sperm count, motility, and morphology [5]. Azoospermia is the absence of spermatozoa on high-powered microscopic examination of at least two samples of seminal fluid [6]. The prevalence of azoospermia has been estimated to be approximately 1% among all men and 10%–15% among infertile men [7].

Exposure to ionizing radiation occurs in diagnostic and therapeutic medicine as well as in the industrial setting [3], and it is also known to cause damage to cells and non-lethal transformation of cells that can result in functional impairment of the testes, as these organs are very radiosensitive [8]. Although an occupational level of radiation exposure would not likely cause azoospermia [9], several previous studies have reported that therapeutic and accidental radiation exposure above certain values could induce azoospermia. We herein present a case of azoospermia in a patient who was exposed to radiation in a non-destructive testing (NDT) facility and discuss the problems of the related monitoring system.

This is a case of an azoospermic patient diagnosed with SCOS which was considered to be caused by occupational radiation exposure. There are many causes of SCOS, including ionizing radiation exposure [13–15]. Medical evaluation of our patient showed no reason to suspect other possible causes of SCOS; thus, considering his job, it is reasonable to assume that patient’s SCOS was caused by occupational radiation exposure.

We assessed the radiation exposure dose and evaluated whether he had fractionated or single exposure to determine whether his condition was caused by radiation, because it is known that spermatogenesis has higher radiation tolerance for single exposure than for fractionated exposure [16]. We inspected the patient’s job history and exposure measurement records (Table 1) and concluded that he was exposed to radiation protractedly for 80 months.

According to the report of the International Atomic Energy Agency, temporary male sterility could result from single short exposure and prolonged exposure doses of 0.15 and 0.4 Gy in a year, respectively, and that permanent male sterility could result from single short exposure and prolonged exposure doses of 3.5–6 and 2 Gy in a year, respectively [17].

Lu et al. showed that fractionated irradiation of 0.7–0.9 Gy was capable of causing oligospermia or azoospermia, but they assumed that spermatogenesis would recover in 1–1.5 years [18]. Howell and Shalet suggested that a fractionated dose of over 1.2 Gy could cause permanent infertility and a dose of over 2 Gy was very likely to cause permanent infertility [19].

Some studies suggested similar levels of exposure dose that cause azoospermia, and a number of studies about azoospermia caused by prolonged exposure to radiation were mainly conducted in patients undergoing radiotherapy for cancer treatment [20–22], and in these studies, some patient developed permanent azoospermia, whereas others experienced transient azoospermia at similar levels of exposure.

The findings of the above-mentioned studies suggest that radiation could induce permanent azoospermia at high exposure doses and that the threshold values vary from person to person, depending on each person’s distinct characteristics. Thus, a person will not necessarily experience azoospermia if exposed to a specific dose. In the present case, the patient was exposed to radiation of 1.926 Gy, which was among the threshold doses mentioned in previous studies, but this value is not usual in normal occupational exposure; the occupational exposure limit in Korea is 100 mSv for 5 years and 50 mSv in any given year. Furthermore, he did not have the evidence of congenital azoospermia or other risk factors. Therefore, it might be reasonable to conclude that his azoospermia was caused by occupational radiation exposure.

On estimating of patient’s exposure dose, we found that the exposure dose records measured through TLD badge did not reflect the actual exposure level. The Korean government has introduced laws about radiation and its control and monitoring of workers who might be exposed and of factories/facilities that handle radioactive material. However, workers might not wear the TLD badge or might use it inappropriately. Accordingly, assessment of radiation exposure with a TLD badge might underestimate the exposure dose, which means that the monitoring of radiation in NDT workers is not working properly. An institution report shows that the mean exposure dose of NDT workers has been increasing, despite the strict government regulations for NDT facilities [23]. It appears that the factories/facilities might be neglecting the regulations and underreporting exposure dose to circumvent government penalties.

Thus, to protect the safety and health of NDT workers, education of workers and strengthening of law enforcement are required to ensure that regulations are strictly followed, and if necessary, the use of cytogenetic dosimeter, such as FISH, for random sampling of NDT workers should be considered.

In this case of azoospermia in an NDT worker who had been exposed to radiation, we noted a difference between the exposure dose on TLD measurement and the actual exposure dose of the patient. Although azoospermia is known to be rarely caused by normal occupational radiation exposure, our patient was exposed to a dose high enough to induce azoospermia in radiation workers. Thus, much attention and efforts are needed to correct this difference in exposure level and prevent health problems.