In 2019, the International Agency for Research on Cancer re-evaluated the carcinogenicity of night-shift work and reported that there is limited evidence that night-shift work is carcinogenic for the development of prostate cancer. Therefore, in 2020 and 2021, the Korean Epidemiologic Investigation Evaluation Committee concluded that 2 cases of prostate cancer were occupational diseases related to the night-shift work. Here, we report the 2 cases of prostate cancer in night-shift workers which were first concluded as occupational diseases by the Korean Epidemiologic Investigation Evaluation Committee.

Patient A: A 61-year-old man worked as a city bus driver for approximately 17 years, from 2002 to 2019, and was exposed to night-shift work during this period. In March 2017, the patient was diagnosed with high-grade prostate cancer through core-needle biopsy after experiencing stinging pain lasting for 2 months. Patient B: A 56-year-old man worked as an electrician and an automated equipment operator in a cement manufacturing plant for 35 years from 1976 to 2013 and was exposed to night-shift work during this period. In 2013, the patient was diagnosed with high-grade prostate cancer through core needle biopsy at a university hospital because of dysuria that lasted for 6 months.

The 2 workers were diagnosed with high-grade prostate cancer after working night shifts for 17 and 35 years respectively. Additionally, previous studies have reported that high-grade prostate cancer has a stronger relationship with night-shift work than low or medium-grade prostate cancer. Therefore, the Korean Epidemiologic Investigation Evaluation Committee concluded that night-shift work in these 2 patients contributed to the development of their prostate cancer.

It is widely known that carbon dioxide (CO₂) arc welding generates carbon monoxide (CO). However, to the best of our knowledge, no case reports have been published regarding CO poisoning in CO₂ arc welders. Therefore, we aimed to report a case of CO poisoning-induced encephalopathy in a CO₂ arc welder in the Republic of Korea to inform about the dangers of CO exposure among CO₂arc welders.

A 40-year-old man working as a CO₂ arc welder for 15 years visited a local hospital with a tremor, involuntary urination, and speaking gibberish, on April 9, 2019. He stated that he had intermittent headache and forgetting symptoms for the last 5 years, and had been lost on the way to work several times. On April 9, 2019, he was diagnosed with CO poisoning-induced encephalopathy through brain magnetic resonance imaging. He received hyperbaric oxygen therapy, and some of his symptoms improved. According to the exposure assessment of his work environment, he was continuously exposed to high concentrations of CO for 15 years while operating CO₂ arc welding machines.

After evaluating the patient's work environment and evaluating his medical history, we concluded that his encephalopathy was caused by CO exposure during CO₂ arc welding. Thus CO₂ arc welders must be aware of the risk of CO poisoning and strive to avoid CO exposure.

Some epidemiological studies have estimated exposure among flight attendants with and without breast cancer. However, it is difficult to find a quantitative evaluation of occupational exposure factors related to cancer development individually in the case of breast cancer in flight attendants. That is, most, if not all, epidemiological studies of breast cancer in flight attendants with quantitative exposure estimates have estimated exposure in the absence of individual flight history data.

A 41-year-old woman visited the hospital due to a left breast mass after a regular check-up. Breast cancer was suspected on ultrasonography. Following core biopsy, she underwent various imaging modalities. She was diagnosed invasive ductal carcinoma of no special type (estrogen receptor positive in 90%, progesterone receptor positive in 3%, human epidermal growth factor receptor 2/neu equivocal) with histologic grade 3 and nuclear grade 3 in the left breast. Neoadjuvant chemotherapy was administered to reduce the tumor size before surgery. However, due to serious chemotherapy side effects, the patient opted for alternative and integrative therapies. She joined the airline in January, 1996. Out of all flights, international flights and night flights accounted for 94.9% and 26.2, respectively. Night flights were conducted at least four times per month. Moreover, based on the virtual computer program CARI-6M, the estimated dose of cosmic radiation exposure was 78.81 mSv. There were no other personal triggers or family history of breast cancer.

This case report shows that the potentially causal relationship between occupational harmful factors and the incidence of breast cancer may become more pronounced when night shift workers who work continuously are exposed to cosmic ionizing radiation. Therefore, close attention and efforts are needed to adjust night shift work schedules and regulate cosmic ionizing radiation exposure.