Increased risk of thyroid cancer in female residents nearby nuclear power plants in Korea: was it due to detection bias?

BACKGROUND: The Korea Radiation Effect & Epidemiology Cohort - The resident cohort (KREEC-R) study concluded that there is no epidemiological or causal evidence supporting any increase in cancer risks resulting from radiation from Korean nuclear power plants (NPPs). But the risks of thyroid cancer in women were significantly higher in residents living near NPPs than control. Debate about the cause of the pattern of thyroid cancer incidence in women is ongoing and some researchers argue that detection bias influenced the result of KREEC-R study. Therefore there was a need to investigate whether residents living near NPPs who were assessed in the KREEC-R were actually tested more often for thyroid cancer. We evaluated the possibility of detection bias in the finding of the KREEC-R study based on materials available at this time. METHODS: Using the KREEC-R raw data, we calculated age standardized rates (ASRs) of female thyroid cancer and re-analyzed the results of survey on the use of medical services. We also marked the administrative districts of residents who received the Radiation Health Research Institute (RHRI) health examinations and those in which thyroid cancer case occurred as per the Chonnam National University Research Institute of Medical Sciences (RIMS) final report on maps where the locations of NPPs and 5 km-radii around them were also indicated. And we compared the incidence rates of Radiation-induced cancer measured between the first period when RHRI health examinations were not yet implemented, and the second period when the RHRI health examinations were implemented. RESULTS: The ASR for the far-distance group, which comprised residents living in areas outside the 30 km radius of the NPPs, increased rapidly after 2000; however, that of the exposed group, which comprised residents living within a 5 km radius of the NPPs, started to increase rapidly even before 1995. The frequencies of the use of medical services were significantly higher in the intermediate proximate group, which comprised residents living within a 5-30 km radius of the NPPs, than in the exposed group in women. In case of female thyroid cancer, the second period ASR was higher than the first period ASR, but in case of female liver cancer and female stomach cancer no significant difference were observed between the periods. On map, many administrative districts of residents who received RHRI health examinations and most administrative districts in which thyroid cancer case occurred on RIMS final report were outside 5 km-radii around NPPs. CONCLUSIONS: We could not find any evidence supporting the assertion that detection bias influenced the increased risks of female thyroid cancer observed in the exposed group of the KREEC-R study, as opposed to the control group.

What causes the experience of discrimination in non-regular workers?

BACKGROUND: Discrimination based on type of employment against non-regular workers is still a social issue. However, there are few studies on job factors that affect the discrimination experience in each type of employment or the association between discrimination and health impact indicators. This study examined occupational health characteristics according to discrimination experience and relating factors that affect discrimination experience. METHODS: This study used the 4th Korean Working Conditions Survey (2014) provided by the Korea Occupational Safety and Health Agency. Among the 50,000 workers, 7731 non-regular wage workers were selected as study population. To examine differences in discrimination experience, we used a t-test on occupational risk factors, occupational stress, occupational characteristics, health impact indicators. To identify the factors that affected discrimination experience, we performed binomial logistic regression analysis. RESULTS: The discrimination experience rate was significantly higher in male, aged less than 40 years old, above high school graduate than middle school graduate, higher wage level, shorter employment period and larger company's scale. As factors related to discrimination experience, they experienced discrimination more as occupational stress was higher and when they were temporary or daily workers rather than permanent workers, work patterns were not consistent, and the support of boss was low. It showed that physical, musculoskeletal, and mental occupational risk scores and subjective job instability were higher and work environment satisfaction was lower in discrimination experienced group. CONCLUSIONS: The present study showed that the demographic and occupational factors were complexly related to discrimination experience in non-regular workers. The experience of discrimination had increased when occupational stress was higher, they were temporary or daily workers rather than permanent workers, work patterns were not consistent, and their boss' support was low. Improving various relating factors, (e.g. occupational stresses, employment status and occupational characteristics), this would ultimately expect to improve non-regular workers' discrimination.

Types of household humidifier disinfectant and associated risk of lung injury (HDLI) in South Korea.

From 2002 through 2015, hundreds of people died of fatal lung injuries associated with the use of humidifier disinfectants (HDs) in Korea. Several chemical disinfectants used for household humidifiers were later clinically confirmed to cause HD-associated lung injury (HDLI). The aim of this study is to evaluate the registered lung disease cases and to compare the distribution of HDLI patients, including deaths, by HD use characteristics including types of HD and HD brands categorized by age group. A total of 530 registered were clinically examined through two rounds of investigations conducted from July 2013 until April 2015. Information on HD use was obtained from a structured questionnaire and home investigations. Approximately one-half of the patients (n=221) were clinically confirmed to be associated with the use of HDs. Pregnant women (n=35, 16%) and pre-school children≤6years old (n=128, 58%) accounted for most of the HD-associated lung injury patients (n=163, 74%). Sixty-seven percent of HDLI patients developed HDLI after less than one year of HD use. HD products containing polyhexamethylene guanidine phosphate (PHMG) were the most frequently used among confirmed HDLI patients (n=123, 55.7%), followed by oligo (2-(2-ethoxy) ethoxyethyl guanidinium (PGH) (n=24, 10.9%) and a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) (n=3, 1.4%). Other HDs did not appear to be linked to HDLI. The majority of the HDLI patients (n=85, 38.5%) was found to use only Oxy Saksak® products containing PHMG. The development of HDLI was clinically found to be associated with the use of several HD products containing PHMG and PGH, and to lesser extent, CMIT/MIT.

Relationship between Exposure to Household Humidifier Disinfectants and Risk of Lung Injury: A Family-Based Study.

BACKGROUND: In South Korea, a cluster of acute lung disease patients included lung injury disease suspected of being caused by the use of humidifier disinfectants. We examined the relationship between humidifier disinfectant exposure and clinically diagnosed humidifier disinfectant-associated lung injury (HDLI) in a family-based study. METHODS: This case-control study included 169 clinically confirmed HDLI cases and 303 family controls who lived with the HDLI patients. A range of information on exposure to humidifier disinfectants was obtained using a structured questionnaire and field investigations. Odds ratios (ORs) and confidence intervals (CIs) were estimated using unconditional logistic regression models that were adjusted for age, sex, presence of a factory within 1 km of residence, and the number of household chemical products used. RESULTS: HDLI risk increased approximately two-fold or more among the highest quartile compared with the lowest quartile in terms of the hours sleeping in a room with an operating humidifier treated with disinfectant (adjusted OR = 2.0, 95 % CI = 1.1-3.7), average hours of disinfectant-treated humidifier use per day (adjusted OR = 2.1, 95 % CI = 1.0-4.5), airborne disinfectant intensity (adjusted OR = 2.6, 95% CI = 1.2-5.3), and cumulative disinfectant inhalation level (adjusted OR = 2.0, 95% CI = 1.0-4.1). HDLI risk increased as the distance of the bed from humidifier gets shorter; compared with longer distance (> 1 m), the odds ratio was 2.7 for 0.5 to 1 m (95 % CI = 1.5-5.1) and 13.2 for <0.5 m (95 % CI = 2.4-73.0). CONCLUSIONS: The use of household humidifier disinfectants was associated with HDLI risk in a dose-response manner.

Visceral fat area-defined obesity and periodontitis among Koreans.

AIM: Although the association of periodontitis with body mass index (BMI)-defined obesity has been studied, it remains controversial. Hence, this study aims to determine whether the obesity is associated with periodontitis among Koreans and to determine the most significant indicator of the obesity on the link. MATERIALS AND METHODS: From the Sihwa-Banwol Environmental Health Cohort, 1046 subjects 15 years of age or older were cross-sectionally surveyed. All participants underwent periodontal and medical health examinations. Age, gender, monthly family income, smoking, drinking, frequency of daily teeth brushing and physical activity were evaluated through interviews. The community periodontal index (CPI) was used to assess periodontitis. BMI, waist circumference (WC), waist hip ratio and visceral fat area (VFA) were used to assess obesity. Multivariate linear and logistic regression analyses were applied. RESULTS: BMI, WC and VFA had a dose-effect relationship with the number of sextants with periodontitis. Although subgroup analysis revealed several significant associations between obesity and periodontitis (CPI 3-4), the greatest association between VFA and periodontitis was found in males, age 45-54 (odds ratio=3.30; 95% confidence interval: 1.53-7.09). CONCLUSIONS: Obesity was associated with periodontitis. VFA was the most suitable indicator of obesity in relation to periodontitis. Obesity may be a substantial risk factor for periodontitis.

Acquired dyschromatopsia among petrochemical industry workers exposed to benzene.

Exposure to organic solvents, which are widely used in industry, can lead to dysfunction of the nervous system. However, controversy continues about the nature of early-stage damage to the nervous system from low-grade chronic exposure to organic solvents. Since loss of color-vision can be a sensitive early marker of neurotoxic damage, the main aim of this study was to investigate the association between low-level chronic exposure to organic solvents, especially benzene, and acquired dyschromatopsia. The study initially comprised 1236 workers who were employed at a large petrochemical distillation factory. After excluding those workers who may have had color-vision impairment due to congenital or acquired eye diseases and those with other medical conditions, 908 males who had worked for at least 6 months were included in the final analysis. Those who worked only in the office were categorized as nonexposed, while those who worked at outside facilities were divided into three groups of approximately equal size according to their estimated cumulative exposure levels to benzene (low, medium, high). Color-vision was assessed using the Lanthony D-15 desaturated panel color test. The results showed that the color-confusion index (CCI) was positively related to age. In the qualitative assessment of types of color-vision loss, the prevalence of total dyschromatopsia was significantly higher with increasing cumulative exposure levels in the left eye (p<0.05) but not in the right eye. The significance for the prevalence of type III dyschromatopsia was borderline in the left eye (p=0.0571). The relationship between acquired dyschromatopsia and exposure level also showed an increase in the odds ratio in the left eye but not in the right eye. Taken together, these results suggest that chronic low-level exposure to benzene can lead to acquired dyschromatopsia.

[The resting electrocardiographic ST segment depression and related factors at a rural adult community, Korea].

OBJECTIVES: To measure the distribution of electrocardiographic ST segment depression, and evaluate its relationships with cardiovascular risk factors based on the cross-sectional studies within a rural Korean community. METHODS: This study analyzed 1,343 persons, over 40 years old, who participated in a baseline survey during 2002-2005; the exclusion criteria included: a past history of myocardial infarction and angina pectoris, and specific conduction abnormalities. A Standard 12 leads ECG was recorded using an FCP-2101 (Fukuda Denshi Co.). The ST segment depression was retrospectively measured by a physician, according to the Minnesota code classification. RESULTS: ST segment depression was found in 3.6 and 6.4% of male and female participants, respectively. After adjusting for age, gender, smoking, physical activity and obesity differences, high blood pressure showed significant relations with ST depression in females (male ORs=2.67, 95% CI=0.85-8.50; female ORs=2.62, 95% CI=1.29-5.32) CONCLUSIONS: As an ischemic ECG sign, ST depression was related to hypertension in female participants. This relationship remained significant, even after cases with left ventricular hypertrophy were removed.

[Study on the relationship between childhood obesity and various determinants, including socioeconomic factors, in an urban area].

OBJECTIVES: This study was conducted to investigate the prevalence of childhood obesity, the association between the undesirable lifestyles and socioeconomic factors, the association between childhood obesity and various risk factors, including socioeconomic factors, and the agreement between the body mass index (BMI) classification and the body fat percentage. METHODS: The study subjects were all the 5th grade students from all the elementary schools in Gunpo City, Kyunggi Province, South Korea (4043 children at 22 schools). The subjects were measured for their height, weight and percent body fat etc. and they were also surveyed by questionnaire from March 18th to April 25th, 2005. To determine whether the children were within normal limits or not, standardized BMIs for each age group were used. The data was analyzed by logistic regression analysis using SAS 9.0 version. RESULTS: The prevalence of childhood obesity prevalence was 25.1%. Boys had a higher prevalence of obesity (27.5%) than did the girls (22.5%). Children had tendencies of having undesirable lifestyles and getting obese if they had a lower socioeconomic status. The risk factors for childhood obesity were low paternal education (OR: 1.17, 95% CI: 0.97-1.42) and non-parental caregivers (OR: 1.34, 95% CI: 0.98-1.82). Other risk factors for childhood obesity were a high birth-weight, longer TV/computer-using time, a lower fruit-eating frequency, short sleeping hours and parental obesity. The agreement rate between the BMI classification and the body fat percentage was 93.1%. CONCLUSIONS: This study showed the children had a higher prevalence of obesity: further, not only individual lifestyles, but also socioeconomic factors could influence childhood obesity. Childhood obesity was especially more problematic for children with a low socioeconomic status.

[Does non-standard work affect health?].

OBJECTIVES: Job insecurity, such as non-standard work, is reported to have an adverse impact on health, regardless of health behaviors. The aim of this study was to examine the relationship between non-standard employment and health in Korea. METHODS: We analyzed a representative weighted sample, which consisted of 2,112 men and 1,237 women, aged 15-64, from the 1998 Korea National Health and Nutrition Examination Survey. Non-standard employment included part-time permanent, short time temporary and daily workers. Self-reported health was used as a health indicator. RESULTS: This study indicated that women were more likely to report poorer health than men with standard jobs. Of all employees, 20.3% were female manual workers. After adjusting for potential confounders, such as age, education, equivalent income, marital, social and self-reported economic status and health behavior factors, nonstandard employment was found to be significantly associated with poor health among female manual workers (OR, 1.86; 95% CI, 1.24 to 2.79). No significant association was found in other working groups CONCLUSIONS: Among female manual workers, nonstandard employees reported significantly poorer health compared with standard workers. This result raises concern as there are increasing numbers of non-standard workers, particularly females.

The association between blood metal concentrations and heart rate variability: a cross-sectional study.

OBJECTIVES: Analysis of heart rate variability (HRV) is useful for measuring cardiovascular autonomic function. The effects of blood metals on cardiovascular autonomic function have not been studied extensively. The objective of the present study was to determine the association between the concentrations of blood metals, including toxic and essential trace elements, and cardiovascular autonomic function, based on HRV, in subjects without clinical cardiovascular diseases. METHODS: The subjects were public officials and their family members (n = 331) in a district of Seoul, Republic of Korea. Age, height, weight, smoking habits, medical history, blood pressure, electrocardiogram (ECG) recording, and chest X-ray were assessed by means of a self-administered questionnaire and medical examination. Blood metal concentrations (blood Pb, As, and Cd; serum Al, Co, Cu, and Zn) were measured by inductively coupled plasma-mass spectrometry. HRV parameters (low frequency, LF; high frequency, HF; total power spectrum, TPS) were measured with LRR-03 and MemCalc software (GMS, Japan). RESULTS: The concentrations of each of the blood metals were almost within normal ranges. Age and heart rate were negatively associated with LF, HF, and TPS (P< 0.01). Whole-blood Cd concentrations were negatively associated with LF (P< 0.01) and HF (P< 0.05). Serum Zn concentrations were positively associated with LF and TPS (P< 0.01). CONCLUSION: Our study suggests that levels of blood metals even within normal ranges may affect heart rate variability.

Variation of systolic blood pressure in rats exposed to cadmium and nickel.

This research was intended to verify separate and combined effects of cadmium and nickel on blood pressure in rats. After cadmium chloride (CdCl(2)) and nickel chloride (NiCl(2)) were administered individually and combined by intraperitoneal injection to rats daily for a week, systolic blood pressure of the tails were measured at 1, 5, 10, 20, and 30 days after administration. Each substance was injected into rats with 0.1 mg/kg x bw and 1.0 mg/kg x bw concentrations. After 0.1 mg/kg x bw CdCl(2) was injected, statistically significant differences from the control group (only saline) were found at 1, 5, and 10 days. After 0.1 mg/kg x bw NiCl(2) was injected, no statistically significant differences from the control group were found. After 0.1 mg/kg x bw CdCl(2) and 0.1 mg/kg x bw NiCl(2) were injected combined simultaneously, statistically significant differences from the control group were found at 1, 5, and 10 days, compared with the 0.1 mg/kg x bw CdCl(2) group after 5 days and the 0.1 mg/kg x bw NiCl(2) group after 5 and 10 days. After 1.0 mg/kg x bw CdCl(2) was injected, statistically significant differences from the control group were found at 1, 5, 10, and 20 days. After 1.0 mg/kg x bw NiCl(2) was injected, statistically significant differences from the control group were found at 1 and 5 days. After 1.0 mg/kg x bw CdCl(2) and 1.0 mg/kg x bw NiCl(2) were injected combined, statistically significant differences were found at 1, 5, 10, 20, and 30 days, compared with 1.0 mg/kg x bw CdCl(2) at 10, 20, and 30 days and 1.0 mg/kg x bw NiCl(2) at 5, 10, 20, and 30 days. It was found that the effect of CdCl(2) on blood pressure was much more than that of NiCl(2) and the combination of CdCl(2) and NiCl(2) in high concentration delayed recovery of blood pressure.