This paper introduces a series of research projects designed to fulfill the societal role of environmental health studies by investigating (1) the dynamic and complex relationships between environmental conditions and (2) health in an urban setting. Research in this first category has revealed the existence of the combined influence of multiple physical environmental factors on health and its mechanisms. In the second category, there have been a number of studies of the integrated influence of social environmental factors on health employing an aggregate modeling of multiple determinants of health and studies of individual topics related to social determinants of health. These research projects have contributed to the formulation of specific remedies and the development of comprehensive health policies. Participatory approaches have been used to enhance capacity building opportunities and to ensure that research results reflect the actual conditions in urban societies. Healthy Cities projects and programs have been developed in close collaboration with this type of research. Urban societies have become interdependent and share the same issues globally. Further research into the relationships between health and the environment in the context of urbanization will expand the base of evidence applicable to the complex realities in modern societies.

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In this study, we aim to compare the criteria for sensitizers among national organizations in various countries and international organizations, and to specify whether each Pollutant Release and Transfer Register (PRTR)-designated chemical substance is a sensitizer by each organization. The definition of sensitizing chemicals and the designation of respective sensitizers according to the PRTR law, Japan Society for Occupational Health (JSOH), American Conference of Governmental Industrial Hygienists (ACGIH), European Union (EU), and Deutsche Forschungsgemeinshaft (DFG) were studied. Of the 435 PRTR-designated chemical substances, 15 are listed as sensitizers according to the PRTR law, 16 as sensitizers of the airway and 21 as sensitizers of the skin by JSOH, 12 as sensitizers (no discrimination) by ACGIH, 19 (airway) and 85 (skin) by EU, and 15 (airway) and 43 (skin) by DFG. Only 9 substances were designated as sensitizers by all these organizations. The variation in the designation of sensitizers is accounted for by the differences in the classification criteria and grouping of chemical substances. JSOH limits the definition of sensitizers to substances that induce allergic reactions in humans and uses only human data. Other organizations utilize not only human evidence but also appropriate animal tests. In addition, EU designates an isocyanate as a sensitizer except those for which there is evidence showing that they do not cause respiratory sensitivity. The worldwide enforcement of the globally harmonized system (GHS) of classification and labeling of chemicals could promote not only the consistent designation of sensitizers among national and international organizations, but also the development of testing guidelines and classification criteria for mixtures.

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Objective: The aim of this study was to determine the level of exposure of mercury (Hg) miners and smelter workers to elemental mercury (Hg⁰) vapor in China, who work in Hg mines without using protective equipment against Hg⁰ vapor. In addition, the level of methylmercury (MeHg) intake by the workers was estimated from the MeHg concentration in their hair.
Methods: Urinary total mercury (THg) and hair THg and MeHg concentrations were measured in 26 Hg miners and smelter workers (i.e., exposed group), and 48 unexposed people (unexposed group).
Results: The exposed group showed high geometric mean THg concentrations in urine (258 ng/ml, 226 μg/g creatinine) and hair (20.0 μg/g). The urinary THg concentration of the smelter workers in particular was extremely high (338 μg/g creatinine in urine). The highest urine THg concentration reached 4577 μg/g creatinine. THg concentrations in urine and hair showed a significant correlation in the exposed group (r=0.62), indicating the adhesion of Hg⁰ vapor to hair. However, no such significant correlation was found in the unexposed group. Hair MeHg concentration in the exposed group (1.97 μg/g) was about threefold higher than that in the unexposed group (0.60 μg/g).
Conclusions: This study shows that smelter workers in a Chinese Hg mine are exposed to extremely high levels of Hg⁰ vapor, and that Hg miners are exposed to higher levels of MeHg than the unexposed subjects. Further study is needed to determine the cause of the higher hair MeHg concentration in the exposed group.

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Objectives: The number of elderly workers has also been increasing and poor psychological well-being in elderly workers has been reported. The aim of this study is to elucidate the factors that are related to poor psychological well-being in elderly workers.
Methods: We administered General Health Questionnaire-12 (GHQ-12) as an indicator of psychological well-being to 330 male elderly workers in the age range of 50-69, and analyzed different psychological factors, namely sense of coherence (SOC), and physical and lifestyle variables such as blood pressure, serum total cholesterol, smoking frequency, alcohol intake, exercise frequency, and body mass index (BMI) that are related to GHQ-12.
Results: When the cut-off point of GHQ-12 was 2/3, 97 workers who showed high GHQ-12 score were classified as one group having poor psychological well-being. A statistically significantly lower SOC score, higher stress score, lower frequency of exercise, higher smoking score and higher BMI, but not longer working hours or higher shift work score in the workers with higher GHQ-12 scores were observed than in the workers with normal GHQ-12 scores. Multiple logistic regression analysis showed that the low SOC score, low frequency of exercise, high smoking frequency and high BMI significantly contributed to the high GHQ-12 score.
Conclusions: A low SOC score in elderly workers is assumed to be directly related to poor psychological well-being, or via the development of lifestyle problems such as lack of exercise, obesity, and smoking in elderly workers. This assumption must be confirmed by conducting future intervention studies on lifestyle.

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Objective: In metropolitan areas in Japan, train commute is very popular that trains are over-crowded with passengers during rush hour. The purpose of this study is to quantify public health risk related to the inhalation of airborne infectious agents in public vehicles during transportation based on a mathematical model.
Methods: The reproduction number for the influenza infection in a train (R_A) was estimated using a model based on the Wells-Riley model. To estimate the influence of environmental parameters, the duration of exposure and the number of passengers were varied. If an infected person will not use a mask and all susceptible people will wear a mask, a reduction in the risk of transmission could be expected.
Results: The estimated probability distribution of R_A had a median of 2.22, and the distribution was fitted to a log-normal distribution with a geometric mean of 2.22 and a geometric standard deviation of 1.53, under the condition that there are 150 passengers, and that 13 ventilation cycles per hour, as required by law, are made. If the exposure time is less than 30 min, the risk may be low. The exposure time can increase the risk linearly. The number of passengers also increases the risk. However, R_A is fairly insensitive to the number of passengers. Surgical masks are somewhat effective, whereas High-Efficiency Particulate Air (HEPA) masks are quite effective. Doubling the rate of ventilation reduces R_A to almost 1.
Conclusions: Because it is not feasible for all passengers to wear a HEPA mask, and improvement in the ventilation seems to be an effective and feasible means of preventing influenza infection in public trains.

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Objectives: The primary objective of this study was to determine the level of knowledge, attitudes and practices (KAP) of rabies management and control of a sample population. The secondary objective was to compare the KAP with respect to rabies management and control between urban and rural areas and between pet and non-pet owners.
Methods: This cross-sectional study was carried out by conducting face-to-face interviews using structured questionnaires among 1570 respondents from selected households in the Kandy District, Sri Lanka.
Results: Approximately 58% of the sample population was pet owners. Among all the respondents, there was a high level of awareness (90%) that dogs are the most common rabies reservoir, that the disease is fatal (79%), and that rabies can be prevented by vaccination (88%). Most of the subjects (96%) would seek treatment from a doctor or a hospital after being bitten by a dog. Although 76% of the respondents said that their pet dogs were vaccinated, only one-half were able to present a vaccination certificate upon request. The subjects from the urban areas would submit the head of an animal for rabies evaluation (69%) compared with those from the rural areas (57%). Pet owners (93%) are more aware that dog rabies vaccines are available from authorized offices than non-pet owners (87%).
Conclusions: The level of awareness of rabies and the level of receptiveness to rabies control measures are high. There is a difference in the attitudes and pet care practices relevant to rabies control between urban and rural areas. Pet owners tend to be more cooperative to rabies control activities. The attitudes and practices of the respondents may reflect the inaccessibility of facilities and the lack of services that would enable community participation in rabies control.

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Objectives: Cancer screening has become common in Japan. However, little is known about the socioeconomic factors affecting cancer screening participation. This study was performed to examine the association between socioeconomic status and cancer screening participation in Japanese males.
Methods: Using the data of 23,394 males sampled from across Japan, the associations between self-reported participation in screenings for three types of cancer (i.e., stomach, lung and colon) and socioeconomic variables, including marital status, types of residential area (metropolitan/nonmetropolitan), household income, and employment status, were examined using multilevel logistic regression by age group (40 to 64 and ³65 years).
Results: The cancer screening participation rates were 34.5% (stomach), 21.3% (lung), and 24.8% (colon) for the total population studied. Being married, living in a nonmetropolitan area, having a higher income and being employed in a large-scale company showed independent associations with a higher rate of cancer screening participation for all three types of cancer. Income-related differences in cancer screening were more pronounced in the middle-aged population than in the elderly population, and in metropolitan areas than in nonmetropolitan areas.
Conclusions: There are notable socioeconomic differences in cancer screening participation in Japan. To promote cancer screening, socioeconomic factors should be considered, particularly for middle-aged and urban residents.

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Objective: To elucidate the prevalence rate of metabolic disorders among subjects with asymptomatic colonic diverticulum.
Methods: We carried out a cross-sectional analysis of the association between colonic diverticulum and selected metabolic disorders among the male personnel of the Self-Defense Forces who underwent total colonoscopy as part of their retirement check-up (age range, 51-59 years).
Results: The prevalence rate of colonic diverticulum was 10.2% among the population studied. The scores of lifestyle factors including those of cigarette smoking and alcohol consumption were similar between the subjects with colonic diverticulum and those without it. Type 2 diabetes (21.6% vs 14.0%, P=0.047) and hypertension (30.9% vs 19.8%, P=0.011) were more prevalent among the subjects with colonic diverticulum than those without it. The prevalence rates of obesity, dyslipidemia, hyperuricemia, and impaired glucose tolerance were similar between the two groups.
Conclusion: The prevalence rates of type 2 diabetes and hypertension are elevated among the middle-aged male subjects with asymptomatic colonic diverticulum. The results may partly explain the reported association between colonic diverticulum and cardiovascular disease.

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