Volume 67, Issue 1, January-December 2025

Key points

What is already known on this topic:

• The relationship between air lead and blood lead has long played a crucial role in establishing occupational lead exposure limits.

• In prior observational studies, data were sparse at relatively low workplace air lead concentrations, and results were limited by short study periods, small sample sizes, and few adjusted potential confounders.

What this study adds:

• This study improves upon prior studies by including a larger sample size and a longer study period, adjusting for a larger variety of potential confounders, and accounting for data correlations among repeated measurements within workers.

• This study provides valuable observational evidence that, at relatively low concentrations, workplace air lead is weakly positively associated with workers' blood lead, which is largely consistent with the findings of prior studies examining similar or higher concentrations.

How this study might affect research, practice, or policy:

• The results of this study indicate that efforts to reduce occupational blood lead levels may warrant consideration of measures beyond reducing air lead exposures, and they call for future observational studies with more comprehensive measurements of lead exposure sources and routes.

Key points: What is already known on this topic: Prior research has recognized the rise of the gig economy and the associated psychological stress due to job instability and uncertainty faced by platform workers. However, there was a lack of a specific measurement tool to assess job-related uncertainty stress among this demographic.

What this study adds: This study introduces the Job-Related Uncertainty Stress Scale for Platform Workers (JUSSPW), a novel instrument developed through rigorous psychometric testing, demonstrating high reliability and validity. The scale provides a comprehensive measure of the uncertainty stress experienced by platform workers, including aspects of work environment, interpersonal relationships, industry regulations, and career development.

How this study might affect research, practice, or policy: The development of the JUSSPW scale has significant implications for future research by offering a standardized tool to assess and compare stress levels among platform workers. It can guide practices in developing targeted interventions to mitigate stress and improve psychological health within this workforce. Policymakers can use these findings to consider regulations that address the unique challenges faced by gig economy workers, potentially leading to improved labor conditions and support systems.

Key points

• Research indicates that individuals in lower-skill occupations face a significantly higher risk of suicide compared with those in higher-skill occupations. Educational attainment also plays a crucial role, as higher education is linked to a lower risk of suicide attempts among non-Hispanic White (NHW) people but not non-Hispanic Black (NHB) people.

• Our study reveals a clear gradient in suicide deaths across occupational skill levels, with a more significant impact observed among NHW people compared with Hispanic people. However, we found that educational attainment plays a protective role by mitigating suicide risk, highlighting the importance of addressing educational disparities.

• The relationship between occupation, education, and suicide risk differs by racial/ethnic group, suggesting the need for targeted interventions.

• These findings call for strategies to improve mental health support in lower-skill occupations, promote educational opportunities, and reduce stigma associated with low-skill jobs. Mental health professionals, policymakers, and educators can use these insights to inform preventative measures.

Key points

What is already known on this topic:

• Technology-related stress is an emerging occupational health concern, with previous studies linking it to decreased productivity and psychological symptoms in certain occupations.

What this study adds:

• In a nationally representative survey of employees across various occupations, techno-insecurity and techno-strain were associated with poor mental health and burnout.

• These health effects were most pronounced in middle-aged and manual workers.

How this study might affect research, practice, or policy:

• Organizational resources are needed to support employees in coping with and working effectively alongside technology.

Key points: We developed a machine learning–based fall risk prediction model using 3 gait features, achieving “excellent” performance with an AUC of 0.909 in men. However, using 5 gait features achieved only “sufficient” performance in women, with an AUC of 0.670.

Key points

What is already known:  

• Workplace loneliness, a work-related dimension of loneliness, has been reported to have detrimental effects on employee health and well-being and organizational productivity.

• Although workplace loneliness should be associated with job turnover, which could result in a huge loss of productivity for the organization, no previous study has examined the prospective association between workplace loneliness and job turnover.

What this study adds:  

• This study found that workplace loneliness, as measured by 3 scales of workplace loneliness, was significantly and positively associated with job turnover at 6-month follow-up among Japanese full-time employees.

How this study might affect research, practice, or policy:  

• This study suggests that workplace loneliness is a risk factor for future job turnover. It provides a rationale for companies/organizations to consider preventing workplace loneliness in order to reduce productivity losses due to employee turnover.

Key points

• What is already known about this topic: Shift workers have a lower prevalence of health behaviors than fixed-day workers. Health literacy (HL) affects health behaviors. However, the mediating role of HL in the relationship between shift work and health behaviors has not hitherto been investigated.

• What this study adds: The lower prevalence of health behaviors among shift workers was not mediated by HL. Our findings suggest that the desynchronization between the circadian rhythm and social environment prevents shift workers from changing their health behaviors.

• How this study might affect research, practice, or policy: Work characteristics and environment should be considered to promote health for working populations engaging in shift work.

Key points

What is already known on this topic: There have been reports of acute lung inflammation caused by polystyrene with different functional groups, but no reports on their chronic effects.

What this study adds: Amino-modified polystyrene had relatively high acute effects compared with unmodified and carboxy-modified polystyrene, but no chronic pulmonary effects were observed with either polystyrene.

How this study might affect research, practice, or policy: The results of this study suggest that lung disorders in the chronic phase caused by differences in the surface functional groups of polystyrene may not be severe.

Key points

Asbestos, a natural fibrous silicate mineral, was designated as an IARC Group 1 carcinogen but many scientific enigmas remained, including the extremely long incubation period and why mesothelial cells are the target of carcinogenesis. Here we describe recent discoveries on asbestos-induced mesothelial carcinogenesis and point out the importance of 3 aspects: affinity of asbestos fibers to hemoglobin and histones, biopersistence, and phagocytic activity of mesothelial cells. This review could be helpful to establish a strategy to prevent mesothelial carcinogenesis in people already exposed to asbestos.

Key points

• The explosive development of nanotechnology has led to the widespread use of engineered nanomaterials. Whether exposure to these materials is harmful remains to be confirmed.

• Exposure of the lungs and other organs to engineered nanomaterials can induce systemic inflammation through increased oxidative stress and activation of inflammasomes, leading to endothelial dysfunction and atherosclerogenesis. It can also result in enhancement of coagulation through the activation of platelets and induction of autonomic nervous system abnormalities via pulmonary reflexes, thus increasing the risk of cardiovascular diseases. Nanomaterials can also translocate into the bloodstream and be taken up by vascular endothelial cells, directly inducing endothelial cell damage.

• Whereas the design of the majority of published toxicological studies is feasible in terms of exposure-effects, further studies using natural delivery routes together with epidemiological studies are needed to confirm the cardiovascular toxicity of nanomaterials through the acceleration of atherosclerogenesis. Further experimental studies are also needed to determine the mechanisms of engineered nanomaterials-induced effects on the cardiovascular system.

Key points

It was not known that 1,2-dichloropropane (1,2-DCP) causes cancer in humans. However, the multiple occurrences of cholangiocarcinoma among workers of a small printing company revealed that 1,2-DCP does cause cancer in humans. This incident led to revisions of the Occupational Safety and Health Act and related regulations in Japan. Furthermore, the International Agency for Research on Cancer (IARC) classified 1,2-DCP as Group 1 (carcinogenic to humans) in 2014.

Key points

In recent years, many reports have been published on the adverse effects of ultrafine particles such as nanoparticles. Initially, most of the reports were about artificially produced manufactured nanomaterials, but reports have now begun to be published on organic polymer compounds and welding fumes unintentionally generated during the manufacturing process. We believe that the adverse effects of nanoparticles on humans are worthy of attention.

Key points

What is already known on this topic: Some industrial chemicals are known to cause carcinogenesis by forming DNA adducts by the interaction of their metabolites with DNA bases. For example, carcinogenic aromatic amines are N-hydroxylated and converted to reactive nitrenium ions to form DNA adducts.

What this study adds: We performed experiments on DNA damage induced by industrial chemicals via the generation of reactive oxygen species and reactive nitrogen species. We found that reactive oxygen species are generated from industrial chemicals and their metabolites and cause oxidative DNA damage. In addition, particles and fibers cause inflammatory responses and the generation of nitric oxide, resulting in nitrative DNA damage.

How this study might affect research, practice, or policy: Our findings provide an insight into the evaluation of carcinogenic risks of industrial chemicals and prevention of carcinogenesis in workplaces.

Key points

• Neurotoxicity of 1-bromopropane was identified by animal experiments and human cases, and reproductive toxicity and carcinogenicity were identified by animal experiments.

• This article clarifies how 1-bromopropane neurotoxicity was discovered and stresses that plural approaches including human, animal, and mechanistic studies were useful in identifying its neurotoxicity.

• Epidemiological studies on the neuro-reproductive toxicity of 1-bromopropane and experimental studies on cancer and non-cancer effects of 1-bromopropane provided evidence for its carcinogenicity based on its effects of oxidative stress, genotoxicity, immunosuppression, and receptor-mediated effects, similar to 2-bromopropane.

• Evidence-based preventive medicine can be established by plural approaches and modification of conventional evidence-based medicine (EBM), which has been developed for therapeutic medicine and is represented by the EBM pyramid.

Key points

• Ortho-toluidine (OT) is a human carcinogen that is absorbed through inhalation, ingestion, and/or skin contact. OT exposure targets the human urinary organs. In 2014-2015, bladder cancer was confirmed in 5 Japanese male workers at a small factory that produces organic dyes and pigment intermediates using 6 aromatic amines including OT.

• This mini-review summarizes the key studies concerning the potential causal relationship between bladder cancer and occupational exposure to OT (mainly through dermal absorption). A clear exposure-dependent increase in the standardized incidence ratio of bladder cancer was observed among Japanese workers exposed primarily to OT, in rat model experiments, and in skin permeability testing evaluating the potent carcinogenicity of OT and other aromatic amines.

• Prolonged dermal exposure to OT along with other genotoxic aromatic amines may cause the development of bladder cancer. An integrative approach applying the use of appropriate occupational hygiene controls and a regular health check-up program combined with assessments of carcinogenicity in experimental animal models and skin permeability is necessary to prevent the development of occupational cancers due to aromatic amines including OT.

Key points

· Organ toxicity: Insoluble forms of indium compounds such as ITO, In₂O₃, In(OH)₃, InAs, InP, and CIGS can be toxic to the respiratory organs of animals when administered to the lungs. In addition to lung damage, ITO nanoparticles can also cause kidney damage, whereas InAs, InP, and ITO can cause testicular damage.

· Carcinogenicity: InP and ITO have demonstrated compelling evidence of their carcinogenic potential in long-term inhalation studies using rats and mice, which was evident in ITO-treated rats. InAs is also suspected to be carcinogenic. Based on the results of these animal experiments, the IARC classified InP as probably carcinogenic to humans (Group 2A) and ITO as possibly carcinogenic to humans (Group 2B).

· Human health risk assessment: Based on the results of animal studies of insoluble indium compounds, attention should be paid to lung carcinogenesis and kidney or testicular damage in addition to interstitial pneumonia and emphysema in human occupational exposure.

Key points

• What is already known on this topic: Work-related musculoskeletal disorders (WMSDs) are a significant concern for India's workforce, directly impacting productivity and economic output. Previous research has shown that occupational risks in Southeast Asia contribute to a substantial disease burden, with 2.04 million disability-adjusted life years attributed to these risks. Over 90% of Indian workers are in the informal economy, lacking adequate workplace health protections, including insurance. Prior studies on WMSDs in India have been fragmented, occupation-specific, and reported varying prevalence rates across sectors, such as agriculture (76% to 99%), manufacturing (47% to 92%), and health care (51% to 100%). However, there has been a lack of national-level meta-estimates, limiting informed decision-making for worker welfare.

• What this study adds: This study provides a comprehensive epidemiological overview of WMSDs across various occupational groups in India, a region underrepresented in global assessments. By conducting a systematic review and meta-analysis, the research offers robust and generalizable prevalence estimates across different occupations. The study identifies the sectors with the highest prevalence of WMSDs and outlines the primary ergonomic and risk factors contributing to these disorders. These data fill a critical gap in occupational health literature, offering valuable insights into the burden of WMSDs in India.

• How this study might affect research, practice, or policy: The findings highlight the need for targeted ergonomic interventions and preventive strategies in high-risk sectors like health care and agriculture. These insights can guide policymakers and occupational health practitioners in developing tailored health programs, potentially reducing WMSD incidence and improving workforce productivity. Implementing these measures could reduce the incidence of WMSDs, lower the economic burden associated with these disorders, and improve overall workforce well-being.

Key points

This study presents a previously unreported case of chronic paronychia with 2 separate digital pilonidal sinuses caused by multiple embedded hair fragments in the eponychium of a dog groomer. The patient had been repeatedly treated with antibiotics without the desired response, ultimately requiring surgical intervention. This case highlights the importance of considering embedded hair as a potential cause of chronic paronychia in individuals with occupations involving hair cutting and grooming, for example, hairdressers, barbers, and dog groomers. The use of protective gloves, hand hygiene, skin care, and thorough removal of loose hair fragments should be emphasized for workers in professions dealing with animal or human hair, as these practices can prevent significant costs for the employee, the employer, and society from sickness absences.