Jai-Dong Moon

Serum hepatic biochemical activity in two populations of workers exposed to styrene

OBJECTIVE To determine whether hepatic biochemical changes, as measured by routinely available tests indicative of hepatocellular necrosis, cholestasis, or altered hepatic clearance of bilirubin, occur in association with low to moderate exposure to styrene commonly experienced in industrial production. METHODS Two independent cross sectional studies were performed comparing serum hepatic transaminases (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), cholestatic enzymes (alkaline phosphatase (AP) and γ glutamyl transpeptidase (GGT)), and bilirubin in (a) 47 workers of fibreglass reinforced plastics who were exposed to styrene and (b) 21 boat and tank fabricators, with separate referent groups of unexposed workers. Exposure to styrene was assessed in air by dosimetry, and in venous blood by headspace analysis. Hepatic biochemical variables were assessed across strata of exposure to styrene defined as 25 ppm in air, or 0.275 mg/l in blood, adjusting for age, sex, body mass index, and ethanol consumption. RESULTS A consistent and significant linear trend for increasing direct bilirubin and direct/total bilirubin ratio was found in association with increasing exposure to styrene, by both air and blood monitoring, in both studies. Mean direct bilirubin concentrations increased from 0.05–0.08 mg% in referents to 0.12–0.19 in workers exposed above 25 ppm, with a significant exposure-response trend (p<0.005). Significantly increased direct/total bilirubin ratios, ranging from 0.22 to 0.35 were associated with exposure to styrene (p<0.001), indicating diminished hepatic clearance of conjugated bilirubin. Also, a significant linear association between the hepatic transaminases ALT and AST and exposure to styrene was found in pooled regression analyses, with an increase in AP of about 10 IU/ml in workers exposed above 25 ppm air or 0.275 mg/l blood styrene in pooled analyses from both studies. CONCLUSIONS The consistent finding of increased direct bilirubin and AP concentrations in these two independent studies provides evidence for diminished hepatic clearance of conjugated bilirubin with associated cholestasis in workers exposed to styrene. The finding of a significant linear association between hepatic transaminase concentrations and exposure to styrene in pooled analyses is consistent with mild hepatic injury and associated metabolic dysfunction.

Coronary artery atherosclerosis associated with shift work in chemical plant workers by using coronary CT angiography

Objectives The aim of this study was to investigate whether shift work is related to elevated risk of coronary artery disease (CAD) by determining the coronary artery calcium (CAC) score and the presence of coronary artery stenosis by using coronary artery CT angiography (CCTA). Methods In this study, 110 male workers participated and underwent a CCTA examination for CAC scoring, which represents coronary artery plaque, and were evaluated for luminal stenosis. All of the participants were working in the same chemical plant, of whom 70 worked day shifts and 40 worked rotating shifts. Results In a multivariate logistic regression analysis, including age, smoking status, alcohol consumption, regular exercise and waist circumference, shift work was associated with a 2.89-fold increase in the odds of developing coronary plaque compared with day work (OR, 2.89; 95% CI 1.07 to 7.82). The association between shift work and coronary plaque was strong after adjustment for age, low-density lipoprotein cholesterol, hypertension and diabetes mellitus (OR, 2.92; 95% CI 1.02 to 8.33). In addition, the number of years of shift work employment was associated with coronary plaque. However, no association was found between shift work and coronary artery stenosis. Conclusions Shift work could induce CAD onset via the atherosclerotic process, and shift work employment duration was associated with an increased risk of atherosclerosis in male workers.

Author response: Coronary artery atherosclerosis associated with shift work in chemical plant workers by using coronary CT angiography

We deeply appreciate the comments and suggestions from Rahman Shiri, MD, PhD. In South Korea, general health check-ups are performed by companies according to their labour management agreement. In this study, coronary artery CT angiography (CCTA) was the investigation specified by the labour management agreement. Prior to the test, the participants in this study were interviewed by a clinician. If the participants had any cardiovascular symptoms or a history of cardiovascular disease, they were transferred to specialist cardiology care and excluded from CCTA. Furthermore, the general population in South Korea can undergo self-referred CCTA evaluation as a general health examination regardless of having a clinical …

Changes in the mean hearing threshold levels in military aircraft maintenance conscripts

ABSTRACT Aircraft maintenance crews are constantly exposed to severe aircraft noise. The purpose of this study was to verify whether noise from aircraft adversely affects the hearing threshold levels (HTLs) of aircraft maintenance conscripts during their 2 years of mandatory military service. This study included 3,000 male aircraft maintenance conscripts who work in the military runway area. We measured and analyzed HTLs at 2–4 kHz. The duration of exposure to noise increased with an increase in rank; however, HTLs showed a tendency to decrease. We attributed such contradicting results to the learning effect and adaptation to military service. However, we suspected that sudden deafness in 6 conscripts (0.2%) was due to loud noise in the runway area during military service. The effectiveness of the hearing conservation program for short-term military service personnel could be increased by focusing on preventing sudden deafness and preenlistment baseline audiogram tests.

Respiratory Syncytial Virus Outbreak in the Basic Military Training Camp of the Republic of Korea Air Force

Objectives: An outbreak of acute febrile illness occurred in the Republic of Korea Air Force boot camp from May to July 2011. An epidemiological investigation of the causative agent, which was of a highly infective nature, was conducted. Methods: Throat swabs were carried out and a multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) assay was performed to identify possible causative factors. Results: The mean age of patients who had febrile illness during the study period was 20.24 years. The multiplex RT-PCR assay identified respiratory syncytial virus (RSV) as the causative agent. The main symptoms were sore throat (76.0%), sputum (72.8%), cough (72.1%), tonsillar hypertrophy (67.9%), and rhinorrhea (55.9%). The mean temperature was 38.75°C and the attack rate among the recruits was 15.7% (588 out of 3750 recruits), while the mean duration of fever was 2.3 days. The prognosis was generally favorable with supportive care but recurrent fever occurred in 10.1% of the patients within a month. Conclusions: This is the first epidemiological study of an RSV outbreak that developed in a healthy young adult group. In the event of an outbreak of an acute febrile illness of a highly infective nature in facilities used by a young adult group, RSV should be considered among the possible causative agents.