Metal exposure is pervasive and not limited to sporadic poisoning events or toxic waste sites. Hundreds of millions of people around the globe are affected by chronic metal exposure, which is associated with serious health concerns, including cancer, as demonstrated in a variety of studies at the molecular, systemic, and epidemiologic levels. Metal-induced toxicity and carcinogenicity are sophisticated and complex in nature. This review provides a broad context and holistic view of currently available studies on the mechanisms of metal-induced carcinogenesis. Specifically, we focus on the five most prevalent carcinogenic metals, arsenic, nickel, cadmium, chromium, and beryllium, and their potential to drive carcinogenesis in humans. A comprehensive understanding of the mechanisms behind the development of metal-induced cancer can provide valuable insights for therapeutic intervention involving molecular targets in metal-induced carcinogenesis.

Arsenic is a naturally occurring, ubiquitous metalloid found in the Earth’s crust. In its inorganic form, arsenic is highly toxic and carcinogenic and is widely found across the globe and throughout the environment. As an International Agency for Research on Cancer–defined class 1 human carcinogen, arsenic can cause multiple human cancers, including liver, lung, urinary bladder, skin, kidney, and prostate. Mechanisms of arsenic-induced carcinogenesis remain elusive, and this review focuses specifically on the role of the PI3K/AKT/mTOR pathway in promoting cancer development. In addition to exerting potent carcinogenic responses, arsenic is also known for its therapeutic effects against acute promyelocytic leukemia. Current literature suggests that arsenic can achieve both therapeutic as well as carcinogenic effects, and this review serves to examine the paradoxical effects of arsenic, specifically through the PI3K/AKT/mTOR pathway. Furthermore, a comprehensive review of current literature reveals an imperative need for future studies to establish and pinpoint the exact conditions for which arsenic can, and through what mechanisms it is able to, differentially regulate the PI3K/AKT/mTOR pathway to maximize the therapeutic and minimize the carcinogenic properties of arsenic.

The coronavirus (COVID-19) pandemic has impacted education systems globally, making digital devices common arrangements for adolescent learning. However, vision consequences of such behavioral changes are not well-understood. This study investigates the association between duration of daily digital screen engagement and myopic progression among 3,831 Chinese adolescents during the COVID-19 pandemic. Study subjects report an average of 2.70 (SD = 1.77), 3.88 (SD = 2.23), 3.58 (SD = 2.30), and 3.42 (SD = 2.49) hours of television, computer, and smartphone for digital learning use at home, respectively. Researchers analyzed the association between digital screen use and myopic symptoms using statistical tools, and find that every 1 h increase in daily digital screen use is associated with 1.26 OR [Odds Ratio] (95% CI [Confidence Interval: 1.21–1.31, p < 0.001]) higher risks of myopic progression. Using computers (OR = 1.813, 95% CI = 1.05–3.12, p = 0.032) and using smartphones (OR = 2.02, 95% CI = 1.19–3.43, p = 0.009) are shown to be associated with higher risks of myopic progression than television use. Results from additional sensitivity tests that included inverse probability weights which accounted for heterogeneous user profile across different device type categories confirm that these findings are robust. In conclusion, this study finds that daily digital screen use is positively associated with prevalence of myopic progression and holds serious vision health implications for adolescents.

The coronavirus disease 2019 (COVID-19) pandemic forced many education systems to consider alternative remote e-learning modalities, which have consequential behavioral and health implications for youth. In particular, increased e-learning engagement with digital screens and reduction in outdoor activities are two likely channels posing adverse risks for myopia development. This study investigated the association between e-learning screen use, outdoor activity, lighting condition, and myopia development among school-age children in China, during the first wave of the COVID-19 pandemic. Data were collected from 3405 school-age children attending primary, lower-secondary, and upper-secondary schools in China. Univariate parametric and nonparametric tests, and multivariate logistic regression analysis were used. Findings show that each diopter hour increase in daily e-learning screen use is significantly associated with progression of myopia symptoms (OR: 1.074, 95% CI: 1.058–1.089; p < 0.001), whereas engaging in outdoor exercise four to six times per week (OR: 0.745, 95% CI: 0.568–0.977; p = 0.034) and one to three times per week (OR: 0.829, 95% CI: 0.686–0.991; p = 0.048) is associated with a lower likelihood of myopia progression than none at all. In addition, we found that indoor lighting that is either “too dim” (OR: 1.686, 95% CI: 1.226–2.319; p = 0.001) or “too bright” (OR: 1.529, 95% CI: 1.007–2.366; p = 0.036) is significantly associated higher likelihood of myopic symptoms. Findings in this study uncover the less observable vision consequences of the COVID-19 pandemic on youths through digital online learning and highlight the importance of considering appropriate mitigation strategies to deal with this emerging public health challenge.

Around the globe, various self-quarantine, social distancing, and school-closure policies were implemented during the coronavirus disease-19 (COVID-19) outbreak to reduce disease transmission. Many economies/territories were compelled to consider digital learning modalities. In particular, increased digital learning engagement with digital devices and mounting psychosocial stress due to social isolation are likely to pose adverse risks for youth visual health globally. This study examines the association between increased digital device use, psychosocial stress, and myopia symptoms among Chinese youth during the COVID-19 pandemic. This is a retrospective observational population study consisting of 3918 participants enrolled in primary, secondary, and university in China. Participants are recruited through an online survey, which included self-reported information on daily digital device use, psychosocial stress level, condition of visual acuity, and demographic information. We utilize statistical tools including χ² test, paired sample t test, and multiple multivariate logistic regression. Each hour increase in digital device use is associated with 1.25 odds ratio OR (95% confidence interval (CI) = 1.21-1.30; P < 0.001) increased risk of developing myopic symptoms, each additional hour of digital device use weighted by near-view and blue-light exposure is associated with OR = 1.04 OR (95% CI = 1.03-1.05; P < 0.001) and OR = 2.25 (95% CI = 1.94-2.60; P < 0.001) increased risk respectively. Subjects reporting under stressful conditions are between OR = 1.98 (95% CI = 1.67-2.36; P < 0.001) and OR = 2.03 (95% CI = 1.71-2.42; P < 0.001) more likely to develop myopic symptoms, relative to those citing less stress. The COVID-19 pandemic led to favorable conditions for myopigenic behavioral changes characterized by extended sedentary engagement with digital devices, which are significantly associated with higher risks of myopia incidence. Relatedly, psychosocial stress accompanying prolonged social isolation during the pandemic is a less noticeable, albeit significant risk factor for myopia development.