Health Effects of Electrolyzed Hydrogen Water for the Metabolic Syndrome and Pre-Metabolic Syndrome: A 3-Month Randomized Controlled Trial and Subsequent Analyses.

We studied the effect of three months' use of electrolyzed hydrogen water (EHW, Electrolyzed Hydrogen Water conditioner produced by Nihon Trim Co., Ltd.) on metabolic and pre-metabolic syndrome groups. This research was carried out jointly by Susaki City; Nihon Trim Co., Ltd.; and Kochi University as part of a local revitalization project with health as a keyword. A randomized, placebo-controlled, double-blind, parallel-group trial was conducted to evaluate the clinical impact of EHW on participants who suffered from metabolic syndrome or pre-metabolic syndrome. EHW was produced via electrolysis using a commercially available apparatus (Nihon Trim Co., Ltd., Osaka, Japan). During exercise, oxidative stress increases, and active oxygen species increase. In this study, we examined 181 subjects with metabolic syndrome or pre-metabolic syndrome. Among the group that drank EHW for 3 months, those who also engaged in a high level of physical activity showed a significant difference in waist circumference reduction. Although no significant difference was observed, several positive results were found in the participants who engaged in a high level of physical activity. Urinary 8-OHdG, urinary nitrotyrosine, HbA1c, and blood glucose levels increased in the filtered water (FW) group but decreased in the EHW group. High-sensitivity CRP increased less in the EHW group. 8-Isoprostane decreased more in the EHW group. In subgroup analysis, the EHW group showed a significantly greater reduction in waist circumference than the FW group only when controlled for high physical activity. Based on the result, we suggest that, among participants in the study who suffered from metabolic syndrome and pre-metabolic syndrome in which the level of active oxygen species is said to be higher than in healthy subjects, the group that consumed EHW and also engaged in a high level of physical activity experienced a suppressed or reduced increase in active oxygen species.

Association of a low chest-to-head circumference ratio with breech or transverse lie: the Japan Environment and Children's Study.

OBJECTIVE: We examined whether the chest-to-head circumference ratio at birth was associated with breech presentation and transverse lie. We also described the obstetric management of such pregnancies in the Japan Environment and Children's Study (JECS). METHODS: We performed a cross-sectional evaluation of data collected between January 2011 and March 2014 in a nationwide prospective birth cohort study, the JECS. We analyzed 83,822 non-anomalous singletons born at 34-41 weeks' gestation to mothers with no history of previous cesareans or uterine surgery. We defined low, normal (reference group), and high chest-to-head circumference ratios as <10th percentile, 10th to 90th percentiles, and >90th percentile, respectively. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for breech presentation and transverse lie. The timing and mode of delivery of such pregnancies were examined. RESULTS: Breech presentation was recorded in 2.6% and transverse lie in 0.2%. A low chest-to-head circumference ratio was associated with increased rate of breech presentation (5.2%; adjusted OR 2.36, 95% CI: 2.10-2.65) and transverse lie (0.3%; adjusted OR 2.33, 95% CI: 1.50-3.60), whereas a high ratio was linked to reduced breech presentation (1.1%; adjusted OR 0.51, 95% CI: 0.39-0.66). Subgroup analysis of children delivered by cesarean (n = 7971) showed a similar association, albeit with slightly reduced strength for breech presentation. Eighty-three percent of breech births and 46.3% of transverse lie births occurred at 37-38 weeks' gestation. Cesarean section was performed in 96.8% of breech presentations and 63.4% of transverse-lie ones. CONCLUSIONS: These findings imply that the fetal chest-to-head circumference ratio may influence presentation at birth.

Asian Intensive Reader of Pneumoconiosis program: examination for certification during 2008-2020.

This study examined physicians' participation and performance in the examinations administered by the Asian Intensive Reader of Pneumoconiosis (AIR Pneumo) program from 2008 to 2020 and compared radiograph readings of physicians who passed with those who failed the examinations. Demography of the participants, participation trends, pass/fail rates, and proficiency scores were summarized; differences in reading the radiographs for pneumoconiosis of physicians who passed the examinations and those who failed were evaluated. By December 2020, 555 physicians from 20 countries had taken certification examinations; the number of participants increased in recent years. Reported background specialty training and work experience varied widely. Passing rate and mean proficiency score for participants who passed were 83.4% and 77.6 ± 9.4 in certification, and 76.8% and 88.1 ± 4.5 in recertification examinations. Compared with physicians who passed the examinations, physicians who failed tended to classify test radiographs as positive for pneumoconiosis and read a higher profusion; they likely missed large opacities and pleural plaques and had a lower accuracy in recognizing the shape of small opacities. Findings suggest that physicians who failed the examination tend to over-diagnose radiographs as positive for pneumoconiosis with higher profusion and have difficulty in correctly identifying small opacity shape.

Association between maternal cholesterol level during pregnancy and placental weight and birthweight ratio: data from the Japan Environment and Children's Study.

BACKGROUND: Placental weight to birthweight ratio (PW/BW ratio), or its inverse, is used as an indicator of placental efficiency. Past studies have shown an association between an abnormal PW/BW ratio and adverse intrauterine environment, however, no previous studies have examined the effect of abnormal lipid levels during pregnancy on PW/BW ratio. We aimed to evaluate the association between maternal cholesterol levels during pregnancy and placental weight to birthweight ratio (PW/BW ratio). METHODS: This study was a secondary analysis using the data from the Japan Environment and Children's Study (JECS). 81 781 singletons and their mothers were included in the analysis. Maternal serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels during pregnancy were obtained from participants. Associations between maternal lipid levels and placental weight and PW/BW ratio were assessed by regression analysis using restricted cubic splines. RESULTS: Dose-response relationships were observed between maternal lipid level during pregnancy and placental weight and PW/BW ratio. High TC and LDL-C levels were associated with heavy placental weight and high PW/BW ratio, i.e., inappropriately heavy placenta for birthweight. Low HDL-C level was also associated with inappropriately heavy placenta. Low TC and LDL-C levels were associated with low placental weight and low PW/BW ratio, i.e., inappropriately light placenta for birthweight. High HDL-C was not associated with PW/BW ratio. These findings were independent of pre-pregnancy body mass index and gestational weight gain. CONCLUSIONS: Abnormal lipid levels such as elevated TC and LDL-C, and low HDL-C level, during pregnancy were associated with inappropriately heavy placental weight.

Influence of chest/head circumference ratio at birth on obstetric and neonatal outcomes: The Japan environment and children's study.

OBJECTIVES: Some newborns that are not small-for-gestational-age (non-SGA, birthweight ≥10th percentile for a given gestational age) may have pathologic growth restrictions. This study examined the association of adverse obstetric and neonatal outcomes with chest/head circumference ratio at birth in non-SGA and SGA newborns. METHODS: This study was a cross-sectional evaluation of data from a nationwide prospective birth cohort study, the Japan Environment and Children's Study. We analyzed 93 690 non-anomalous singletons born at 34-41 gestational weeks. We defined low, normal, and high chest/head circumference ratio as <10th percentile, 10th-90th percentile, and >90th percentile, respectively, according to the internally constructed chest/head circumference percentile chart. Modified Poisson regression was used to estimate adjusted prevalence ratios (aPR) for the outcomes studied. RESULTS: Compared with non-SGA newborns with a normal ratio, those with a low ratio had an increased occurrence of low birthweight (1.75, 1.58-1.94 [aPR, 95% confidence interval]), cesarean delivery (1.34, 1.29-1.38), Apgar score <7 at 5 min (1.57, 1.14-2.17), respiratory complications (1.20, 1.04-1.39), and prolonged hospitalization (1.36, 1.30-1.42). In contrast, the high-ratio group had a lower rate of low birthweight (0.71, 0.59-0.86), cesarean delivery (0.82, 0.77-0.87), and prolonged hospitalization (0.83, 0.78-0.89). In SGA newborns, a low ratio was associated with increased aPRs for low birthweight, cesarean delivery, hypoglycemia, and prolonged hospitalization, whereas a high ratio showed no such association. CONCLUSIONS: Findings indicate that the chest/head circumference ratio at birth influence obstetric and neonatal outcomes regardless of the birthweight status.

Perceptual and objective physical quality of chest images: a comparison between digital radiographic chest images processed for cancer screening and pneumoconiosis screening in Japan.

This study (1) evaluated the perceptual and objective physical quality of digital radiographic chest images processed for different purposes (routine hospital use, lung cancer screening, and pneumoconiosis screening), and (2) quantified objectively the quality of chest images visually graded by the Japan National Federation of Industrial Health Organization (ZENEIREN). Four observers rated the images using a visual grading score (VGS) according to ZENEIREN's quality criteria. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured. Between groups, differences were assessed using ANOVA (followed by Bonferroni multiple comparisons) or unpaired t-test. The Pearson's correlation coefficients were calculated for the correlation between perceptual quality and objective physical image quality. The image quality perceived by the observers and the SNR measurements were highest for the images generated using parameters recommended for lung cancer screening. The images processed for pneumoconiosis screening were rated poorest by the observers and showed the lowest objective physical quality measurements. The chest images rated high quality by ZENEIREN generally showed a higher objective physical image quality. The SNR correlated well with VGS, but CNR did not. Highly significant differences between the processing parameters indicate that image processing strongly influences the perceptual quality of digital radiographic chest images.

Association between the ratio of placental weight to birthweight and the risk of neurodevelopmental delay in 3-year-Olds: The Japan environment and Children's study.

INTRODUCTION: The ratio of placental weight to birthweight (PW/BW ratio) is well known as a simple indicator of the prenatal intrauterine environment and placental functioning. We assessed the impact of PW/BW ratio on the risk of neurodevelopmental delay in 3-year-olds. METHODS: We used data of 71 205 mother-child pairs enrolled in the Japan Environment and Children's Study. Low PW/BW ratio was defined as a PW/BW ratio below the 10th percentile of the study population, high PW/BW ratio was defined as above the 90th percentile, and normal PW/BW ratio was defined as between the low and high PW/BW ratio. Neurodevelopment was assessed using the Japanese translation of the Ages and Stages Questionnaires, third edition. Associations between PW/BW ratio and risk of developmental delay were examined using multivariable models. RESULTS: Compared with boys in the normal PW/BW group, boys in the high PW/BW group had higher risk for developmental delays in all domains except fine motor skills (communication: adjusted risk ratio [aRR], 1.17; 95% confidence interval [CI], 1.04-1.33; gross motor skills: aRR, 1.28; 95% CI, 1.13-1.46; problem solving: aRR, 1.20; 95% CI, 1.09-1.31; personal-social: aRR, 1.26; 95% CI, 1.10-1.43), and boys in the low PW/BW group also had higher risk for developmental delays in some domains. For girls, there was almost no association between PW/BW ratio and developmental delay. DISCUSSION: An unbalanced PW/BW ratio, especially high PW/BW ratio, might indicate intrauterine suboptimality, which affects child neurodevelopment in a sex-specific manner.

Gestational weight gain mediates the effects of energy intake on birth weight among singleton pregnancies in the Japan Environment and Children's Study.

BACKGROUND: Extra energy intake is commonly recommended for pregnant women to support fetal growth. However, relevant data regarding variations in energy intake and expenditure, body mass index and gestational weight gain (GWG) are frequently not considered. This study aimed to investigate how energy intake during pregnancy and gestational weight gain (GWG) are associated with birth weight. METHODS: Early pregnant women were recruited into a Japanese nationwide prospective birth cohort study between 2011 and 2014. We analysed data of 89,817 mother-child pairs of live-born non-anomalous singletons after excluding births before 28 weeks or after 42 weeks. Energy intake during pregnancy was estimated from self-administered food frequency questionnaires (FFQ) and was stratified into low, medium, and high. Participants completed the FFQ in mid-pregnancy (mean 27.9 weeks) by recalling food consumption at the beginning of pregnancy. Effects of energy intake on birth weight and mediation by GWG were estimated using the Karlson-Holm-Breen method; the method separates the impact of confounding in the comparison of conditional and unconditional parameter estimates in nonlinear probability models. Relative risks and risk differences for abnormal birth size were calculated. RESULTS: Mean daily energy intake, GWG, and birth weight were 1682.1 (533.6) kcal, 10.3 (4.0) kg, and 3032.3 (401.4) g, respectively. 6767 and 9010 women had small-for-gestational-age and large-for-gestational-age infants, respectively. Relative to low energy intake, moderate and high intakes increased adjusted birth weights by 13 g and 24 g, respectively: 58 and 69% of these effects, respectively, were mediated by GWG. Compared with the moderate energy intake group, the low energy intake group had seven more women per 1000 women with a small-for-gestational-age birth, whereas the high energy intake group had eight more women per 1000 women with a large-for-gestational-age birth. CONCLUSION: GWG mediates the effect of energy intake on birth weight. All pregnant women should be given adequate nutritional guidance for optimal GWG and fetal growth.

Breastfeeding and risk of febrile seizures in the first 3 years of life: The Japan Environment and Children's Study.

OBJECTIVE: Our study was conducted to examine the association between breastfeeding and febrile seizures (FS) in the first 3 years of life. METHODS: We analyzed the dataset of the Japan Environment and Children's Study (JECS), which is a birth cohort study undertaken to elucidate the influence of environmental factors on children's health during the fetal period and early childhood. Information on feeding duration and feeding pattern, as well as information on febrile seizures, were obtained from questionnaires sent to mothers/caregivers. We categorized a child as having experienced FS if the child was reported as having been diagnosed with FS in the first 3 years. Modified Poisson regression with a robust error variance was used to estimate the effect of duration of breastfeeding and the risk of FS. RESULTS: Of the 84,321 children included in the analysis, 6264 (7.4%) were reported to have experienced FS at least once in the first 3 years of life. Multivariate analyses showed that the risk of FS during the first 3 years of life tended to decrease as the duration of breastfeeding increased. Male sex and frequent fever episodes were also associated with an increased risk of FS. CONCLUSIONS: Continued breastfeeding until 2 years of age, the most susceptible age for FS, had a small but protective effect on FS.

Inter-observer agreement and accuracy in classifying radiographs for pneumoconiosis among Asian physicians taking AIR Pneumo certification examination.

This study examined inter-observer agreement and diagnostic accuracy in classifying radiographs for pneumoconiosis among Asian physicians taking the AIR Pneumo examination. We compared agreement and diagnostic accuracy for parenchymal and pleural lesions across residing countries, specialty training, and work experience using data on 93 physicians. Physicians demonstrated fair to good agreement with kappa values 0.30 (95% CI: 0.20-0.40), 0.29 (95% CI: 0.23-0.36), 0.59 (95% CI: 0.52-0.67), and 0.65 (95% CI: 0.55-0.74) in classifying pleural plaques, small opacity shapes, small opacity profusion, and large opacities, respectively. Kappa values among Asian countries ranging from 0.25 to 0.55 (pleural plaques), 0.47 to 0.73 (small opacity profusion), and 0.55 to 0.69 (large opacity size). The median Youden's J index (interquartile range) for classifying pleural plaque, small opacity, and large opacity was 61.1 (25.5), 76.8 (29.3), and 88.9 (23.3), respectively. Radiologists and recent graduates showed superior performance than other groups regarding agreement and accuracy in classifying all types of lesions. In conclusion, Asian physicians taking the AIR Pneumo examination were better at classifying parenchymal lesions than pleural plaques using the ILO classification. The degree of agreement and accuracy was different among countries and was associated with background specialty training.

Dose-response relationships between maternal urinary cotinine and placental weight and ratio of placental weight to birth weight: The Japan Environment and Children's Study.

INTRODUCTION: Studies on the relationship between maternal self-reported smoking status and placental weight report inconsistent results. This study examined the relationships between maternal urinary cotinine concentration and placental weight and the ratio of placental weight to birth weight (PW/BW ratio). The study also examined the relationship between maternal smoking status, as determined by cotinine concentration, with placental weight and with PW/BW ratio, stratified by sex of offspring. METHODS: Our analysis used information of 91,049 mother-child pairs enrolled in the Japan Environment and Children's Study. Maternal urinary cotinine concentration was quantified (during the second or third trimester) with high-performance liquid chromatography-tandem mass spectrometry. Using restricted cubic splines, placental weight and PW/BW ratio were plotted against natural log-transformed cotinine concentration. Taking cotinine levels of <0.17 ng/mL, 0.17 to <21.5 ng/mL (natural log-transformed values, -1.77 to 3.07), and ≥21.5 ng/mL as indicative of non-smokers, passive smokers, and active smokers, respectively, the relationships between maternal smoking status and placental weight and PW/BW ratio were examined, adjusting for confounders. RESULTS: Placental weight and PW/BW ratio increased with increasing cotinine concentration. After cotinine reached a certain concentration, the placental weight decreased in male offspring whereas it plateaued in female offspring. Compared with not smoking, active smoking during pregnancy significantly increased placental weight and PW/BW ratio. CONCLUSION: Placental weight responded as an inverted U-shape whereas the PW/BW ratio followed a J-shape with increasing maternal urinary cotinine concentration measured during pregnancy, suggesting exposure to tobacco smoke induces a disproportionate reduction in fetal growth. The effect of tobacco smoke on placental growth varied by sex of offspring.

Risk assessment of farmers handling pelleted seeds containing crystalline silica and attapulgite.

OBJECTIVES: This study aimed to assess the risk to farmers from handling pelleted seeds that include crystalline silica and attapulgite. METHODS: We measured personal exposure levels to respirable crystalline silica and attapulgite in the experimenter representing a farmer in a simulated workplace. From these values, the annual occupational exposure levels were estimated and compared with the established occupational exposure limits. To assess the toxicity of respirable crystalline silica and attapulgite, digital chest images of workers in a factory producing pelleted seeds were examined. RESULTS: The personal exposure measurement results showed that the concentrations of total dust, respirable dust, and respirable crystalline silica generated during work handling of pelleted seeds were 0.27, 0.06, and 0.00043 mg/m3 , respectively. The estimated annual occupational exposure level to total dust, respirable dust, and respirable crystalline silica in farmers was 103 to 104 times lower than established occupational exposure limits. Attapulgite was not detected by analysis of the pelleted seeds themselves or dust collected during the personal exposure measurements. No pulmonary parenchymal or pleural lesions were detected in the digital chest images of the factory workers. CONCLUSION: We found that farmers handling pelleted seeds would not be exposed to levels of total dust, respirable dust, respirable crystalline silica, and attapulgite derived from pelleted seeds exceeding occupational exposure limits. These results suggest that the risk to farmers of handling pelleted seeds is negligible.

Lack of concern about body image and health during pregnancy linked to excessive gestational weight gain and small-for-gestational-age deliveries: the Japan Environment and Children's Study.

BACKGROUND: Pregnant women in Japan express various reasons for limiting gestational weight gain (GWG). We aimed to identify and characterise groups where the women share common reasons to limit GWG and to examine how these groups are associated with inappropriate GWG and abnormal foetal size. METHODS: We prospectively studied information from the Japan Environment and Children's Study (JECS) on 92,539 women who gave birth to live singletons from 2011 through 2014. Pregnant women were recruited during early pregnancy. Their reasons for limiting GWG and other information were collected through self-reported questionnaires and medical records. We applied latent class analysis to group the women based on their reported reasons. We used multinomial logistic regression to compare the risks of inappropriate (inadequate and excessive) GWG and abnormal foetal size (determined by new-born weight for gestational age) between the identified groups. RESULTS: We identified three groups: Group 1 (76.7%), concerned about delivery and new-born health (health-conscious women); Group 2 (14.5%), concerned about body shape, delivery, and new-born health (body-shape- and health-conscious women); and Group 3 (8.8%), women without strong reasons to limit GWG (women lacking body-shape and health consciousness). Compared with Group 1 members, Group 2 members tended to be younger, have lower pre-pregnancy weight, be unmarried, be nulliparous, have practiced weight loss before pregnancy, and not have chronic medical conditions. Group 3 members tended to be less educated, unmarried, multiparous, smokers, and have a higher prevalence of pre-pregnancy underweight and previous caesarean delivery. Relative to Group 1, Group 2 had a lower unadjusted risk for inadequate GWG (relative risk ratio [RRR] = 0.86, 95% CI: 0.81-0.90) and large-for-gestational-age birth (RRR = 0.91, 95% CI 0.86-0.97), whereas Group 3 had a higher unadjusted risk for excessive GWG (RRR = 1.36, 95% CI: 1.29-1.43) and small-for-gestational-age (SGA) births (RRR = 1.15, 95% CI: 1.05-1.25). CONCLUSIONS: In this Japanese nationwide birth cohort study, pregnant women who were less conscious about body shape and health had complex risks for excessive GWG and SGA birth. Health care providers should consider a woman's perception of GWG when addressing factors affecting GWG and foetal growth.

Radiographic diagnosis of Pneumoconioses by AIR Pneumo-trained physicians: Comparison with low-dose thin-slice computed tomography.

OBJECTIVES: The Asian Intensive Reader of Pneumoconiosis (AIR Pneumo) is a training program designed to improve diagnostic skills for chest radiographies (CXRs) in accordance with the ILO/ICRP 2000. The purpose was to determine the prevalence of occupational environmental pulmonary disease findings in construction workers on thin-slice computed tomography (thin-slice CT), and to compare the diagnostic performance with CXR evaluated by AIR Pneumo-trained physicians. METHODS: Ninety-seven male construction workers underwent low-dose thin-slice CT and CXR on the same day. NIOSH B reader and a board-certified radiologist each interpreted the thin-slice CTs independently. The concordant findings on thin-slice CT were established as the reference standard and were statistically compared with CXRs. Four physicians interpreted CXRs independently according to the ILO/ICRP 2000. RESULTS: Of the 97 cases, nine showed irregular or linear opacities, and 44 had pleural plaques on thin-slice CT. Five, four, three, and two of nine cases with irregular opacity were detected by the four readers on CXRs, respectively. Sixteen, 14, 9, and 5 of the 44 cases with pleural plaques were detected by the four readers, respectively. Specificities for irregular opacities ranged from 94% to 100%, and those for pleural plaques were from 86% to 96%. CONCLUSIONS: Thin-slice CT-detected irregular opacity was found in 9.3%, whereas pleural plaque was found in 45.4% among the construction workers. Chest radiography showed acceptable performance in classifying pneumoconiotic opacities according to ILO/ICRP 2000 by the AIR Pneumo and/or NIOSH-certified physicians.

Association between maternal hemoglobin concentration and placental weight to birthweight ratio: The Japan Environment and Children's Study (JECS).

INTRODUCTION: Past studies have shown that maternal anemia is associated with a heavy placenta or a higher placental weight/birthweight (PW/BW) ratio. Although these findings suggest a non-linear relationship between maternal hemoglobin concentration and PW/BW ratio, this relationship has not been closely examined. METHODS: We evaluated 83,354 singletons and their mothers in a nation-wide birth cohort study, the Japan Environment and Children's Study (JECS). The associations between maternal hemoglobin concentration and placental weight, birthweight, and PW/BW ratio were assessed. RESULTS: Mean placental weight was significantly higher in women with moderate or severe anemia (576 [183] g), but not in women with elevated hemoglobin levels (564 [117] g), compared with in women with normal hemoglobin levels (560 [115] g). In contrast, mean PW/BW ratio was significantly higher in women with moderate or severe anemia (0.190 [0.049]) or elevated hemoglobin levels (0.189 [0.033]) than in women with normal hemoglobin levels (0.185 [0.033]). In a regression analysis with cubic spline, a U-shaped relationship was found between maternal hemoglobin concentration and PW/BW ratio. DISCUSSION: We demonstrated non-linear and concentration-dependent relationships between maternal hemoglobin concentration and placental weight, birthweight, and PW/BW ratio. Although the mechanisms underlying these associations are not fully understood, we suggest that low or elevated hemoglobin concentration may lead to placental compensatory hypertrophy and fetal growth restriction. Prevention and proper management of anemia before and during pregnancy are important for a well-functioning placenta and favorable fetal growth.

Potential asbestos exposure among patients with primary lung cancer in Japan.

OBJECTIVE: To investigate the extent of asbestos exposure among patients with primary lung cancer in Japan. METHODS: A retrospective estimation of potential asbestos-exposed individuals, as determined by the presence of pleural plaques identified on chest computed tomography (CT), was conducted on 885 pathologically confirmed primary lung cancer patients (mean age 71.3 years, 641 males). All patients were diagnosed at 29 hospitals across Japan between 2006 and 2007. Since these hospitals belong to the Japan Federation of Democratic Medical Institutions (MIN-IREN), an organization of medical institutions for workers, the study subjects may contain a higher proportion of workers than the general population. RESULTS: Pleural plaques were identified in 12.8% of subjects (15.8% in males and 4.9% in females), consisting exclusively of cases older than 50 years. They were found most frequently on the chest wall pleura (96.5%), followed by the diaphragm (23.9%) and mediastinum (9.7%). Calcifications were seen in 47 cases (41.6%). The highest prevalence of pleural plaques was seen among workers from construction-related fields (37.7%). No distinct lung cancer histology was observed in patients with pleural plaques. Coexistence of pleural plaques and small irregular opacities was observed in 2.5% of subjects. CONCLUSION: In a Japanese population representing more workers than general Japanese, 12.8% of patients with primary lung cancer may have experienced asbestos exposure at some time in the past. Special medical attention should be paid to individuals with a history of employment in construction-related occupations, as workers in this sector showed the highest prevalence of pleural plaques.