Ambient benzene at the residence and risk for subtypes of childhood leukemia, lymphoma and CNS tumor

miR-451a and miR-486-5p: biomarkers for benzene-induced hematotoxicity

The hematopoietic system is the primary target of benzene exposure. Whether peripheral blood miRNA can serve as sensitive biomarkers for benzene-induced hematopoietic damage has attracted considerable attention. This study focuses on exploring the role of miR-451a and miR-486-5p in benzene-induced erythroid damage and assessing their potential as biomarkers of benzene-induced hematotoxicity. Animal experiments and human studies were conducted to reveal expression patterns of miR-451a and miR-486-5p in bone marrow and peripheral blood after benzene exposure, along with their correlations with erythrocyte indices. In C57BL/6J mice exposed to benzene, the expression levels of miR-451a and miR-486-5p in bone marrow decreased, which also positively correlated with red blood cell count (RBC), hemoglobin (Hb), and hematocrit (HCT). Conversely, in peripheral blood of C57BL/6J mice, the expression levels of the two miRNAs increased and showed a negative correlation with the three erythroid indices. Subsequent validation in bone marrow samples of chronic benzene poisoning patients and peripheral blood of workers from petrochemical plant confirmed significant correlations between miR-451a and miR-486-5p expression levels and red blood cell parameters. Furthermore, receiver operator characteristic (ROC) curve analyses revealed that miR-451a emerged as a potential biomarker for benzene-induced hematotoxicity, exhibiting superior discriminatory power compared to miR-486-5p and conventional erythroid indices. Additionally, in vitro experiments using K562 cells revealed differential regulatory effects of benzene metabolite hydroquinone (HQ) on miR-451a expression based on erythroid differentiation status. These findings emphasized the important role of miR-451a and miR-486-5p in benzene-induced erythrogenesis disruption, offering valuable insights for biomarker development and therapeutic interventions.

Characteristics and microscopic mechanisms of smoke emissions of OMMT/SBS-modified asphalt

Nanomaterials are increasingly being used in road engineering with the development of road construction technology. The smoke suppression performance of asphalt can be substantially improved using organic nano-montmorillonite (OMMT)/styrene-butadiene-styrene (SBS) block modifiers. Pyrolysis gas chromatography-mass spectrometry (PY-GC-MS), fluorescence microscopy (FM), thermogravimetric analysis (TG), and gel permeation chromatography (GPC) were used to explore the characteristics and microscopic mechanisms of flue gas emissions. The addition of OMMT effectively reduced the emissions of carbon dioxide and Volatile Organic Compounds (VOCs) in asphalt flue gas, as well as increased the SBS swelling degree in the asphalt matrix and the compatibility between the SBS and asphalt matrix. The stable interlayer structure formed via OMMT/SBS co-modification effectively inhibited the release of VOCs during the thermal decomposition of asphalt, being more environmentally friendly because of the reduction in emissions compared with traditional asphalt. The SBS, OMMT, and asphalt matrix is a physically modified mixture. The incorporation of OMMT increases the macromolecule content in the modified asphalt, showing that OMMT inhibited the decomposition of asphalt macromolecules into smaller molecules, thus reducing the release of VOCs. Including the appropriate macro and small molecules helps strengthen the ability of asphalt to resist permanent deformation at high temperatures, maintain its flexibility, and effectively prevent cracking at low temperatures.

PM2.5, vegetation density, and childhood cancer: a case-control registry-based study from Texas 1995-2011

BACKGROUND

Air pollution is positively associated with some childhood cancers, whereas greenness is inversely associated with some adult cancers. The interplay between air pollution and greenness in childhood cancer etiology is unclear. We estimated the association between early-life air pollution and greenness exposure and childhood cancer in Texas (1995 to 2011).

METHODS

We included 6101 cancer cases and 109 762 controls (aged 0 to 16 years). We linked residential birth address to census tract annual average fine particulate matter <2.5 µg/m³ (PM2.5) and Normalized Difference Vegetation Index (NDVI). We estimated odds ratios (ORs) and 95% confidence intervals (CIs) between PM2.5/NDVI interquartile range increases and cancer. We assessed statistical interaction between PM2.5 and NDVI (likelihood ratio tests).

RESULTS

Increasing residential early-life PM2.5 exposure was associated with all childhood cancers (OR = 1.10, 95% CI = 1.06 to 1.15), lymphoid leukemias (OR = 1.15, 95% CI = 1.07 to 1.23), Hodgkin lymphomas (OR = 1.27, 95% CI = 1.02 to 1.58), non-Hodgkin lymphomas (OR = 1.24, 95% CI = 1.02 to 1.51), ependymoma (OR = 1.27, 95% CI = 1.01 to 1.60), and others. Increasing NDVI exposure was inversely associated with ependymoma (0- to 4-year-old OR = 0.75, 95% CI = 0.58 to 0.97) and medulloblastoma (OR = 0.75, 95% CI = 0.62 to 0.91) but positively associated with malignant melanoma (OR = 1.75, 95% CI = 1.23 to 2.47) and Langerhans cell histiocytosis (OR = 1.56, 95% CI = 1.07 to 2.28). There was evidence of statistical interaction between NDVI and PM2.5 (P < .04) for all cancers.

CONCLUSION

Increasing early-life exposure to PM2.5 increased the risk of childhood cancers. NDVI decreased the risk of 2 cancers yet increased the risk of others. These findings highlight the complexity between PM2.5 and NDVI in cancer etiology.

Registration, incidence patterns, and survival trends of central nervous system tumors among children in Germany 1980-2019: An analysis of 40 years based on data from the German Childhood Cancer Registry

BACKGROUND

Tumors of the central nervous system (CNS) are the second most common type of pediatric cancer in Germany. We aimed to describe registration practice, incidence, and survival patterns for childhood CNS tumors in Germany for the past 40 years.

PROCEDURE

Including all CNS tumor cases in children diagnosed at ages 0-14 years registered at the German Childhood Cancer Registry (GCCR) in 1980-2019 (for survival analysis 1980-2016), we calculated age-specific and age-standardized incidence rates (ASIR) over time, average annual percentage changes (AAPC), and 1- and 5-year overall survival.

RESULTS

While we observed a pronounced increase in ASIR after the establishment of the GCCR during the 1980s, ASIR for all pediatric CNS tumors combined continued to increase markedly from 28.6 per million in 1990-1999 to 43.3 in 2010-2019 (AAPC = 2.7% in 1991-2010, AAPC = 0.3% in 2010-2019). The 5-year overall survival from CNS tumors improved from 63% in the 1980s, 70% in the 1990s to 79% in 2010-2016. These improvements have occurred across all age groups. Children diagnosed with ependymomas and choroid plexus tumors experienced the strongest increase (from 54% to 81%).

CONCLUSIONS

Observed increases in incidence rates for pediatric CNS tumors are likely only partially caused by actual increasing case numbers. The majority is a function of improved registration and, to a minor extent, improvements in diagnostics. Survival from pediatric CNS tumors has, by and large, improved consistently, leading to a growing population of childhood cancer survivors with diverse health biographies and risk of lifelong adverse impact on health and wellbeing.

Examining the relationship between land use and childhood leukemia and lymphoma in Tehran

We conducted a hospital-based case-control study to explore the association between proximity to various land use types and childhood leukemia and lymphoma. This research involved 428 cases of childhood leukemia and lymphoma (2016-2021), along with a control group of 428 children aged 1-15 in Tehran. We analyzed the risk of childhood cancer associated with land use by employing logistic regression adjusted for confounding factors such as parental smoking and family history. The odds ratio (OR) for children with leukemia and lymphoma residing within 100 m of the nearest highway was 1.87 (95% CI = 1.00-3.49) and 1.71 (95% CI = 1.00-2.93), respectively, in comparison to those living at a distance of 1000 m or more from a highway. The OR for leukemia with exposure to petrol stations within 100 m was 2.15 (95% CI = 1.00-4.63), and for lymphoma it was 1.09 (95% CI = 0.47-2.50). A significant association was observed near power lines (OR = 3.05; 95% CI = 0.97-9.55) within < 100 m for leukemia. However, no significant association was observed between power lines and the incidence of childhood lymphoma. There was no association between bus stations, major road class 2, and the incidence of childhood leukemia and lymphoma. In conclusion, our results suggest a possible association between the incidence of childhood leukemia and proximity to different urban land uses (i.e., highways and petrol stations). This study is the first step in understanding how urban land use affects childhood leukemia and lymphoma in Tehran. However, comprehensive studies considering individual-level data and specific pollutants are essential for a more nuanced understanding of these associations.

Characterization of VOC emissions and health risk assessment in the plastic manufacturing industry

Volatile organic compounds (VOCs) significantly contribute to ozone pollution formation, and many VOCs are known to be harmful to human health. Plastic has become an indispensable material in various industries and daily use scenarios, yet the VOC emissions and associated health risks in the plastic manufacturing industry have received limited attention. In this study, we conducted sampling in three typical plastic manufacturing factories to analyze the emission characteristics of VOCs, ozone formation potential (OFP), and health risks for workers. Isopropanol was detected at relatively high concentrations in all three factories, with concentrations in organized emissions reaching 322.3 μg/m3, 344.8 μg/m3, and 22.6 μg/m3, respectively. Alkanes are the most emitted category of VOCs in plastic factories. However, alkenes and oxygenated volatile organic compounds (OVOCs) exhibit higher OFP. In organized emissions of different types of VOCs in the three factories, alkenes and OVOCs contributed 22.8%, 67%, and 37.8% to the OFP, respectively, highlighting the necessity of controlling them. The hazard index (HI) for all three factories was less than 1, indicating a low non-carcinogenic toxic risk; however, there is still a possibility of non-cancerous health risks in two of the factories, and a potential lifetime cancer risk in all of the three factories. For workers with job tenures exceeding 5 years, there may be potential health risks, hence wearing masks with protective capabilities is necessary. This study provides evidence for reducing VOC emissions and improving management measures to ensure the health protection of workers in the plastic manufacturing industry.

Environmental Pollution and Risk of Childhood Cancer: A Scoping Review of Evidence from the Last Decade

The long-term effects of environmental pollution have been of concern as several pollutants are carcinogenic, potentially inducing a variety of cancers, including childhood cancer, which is a leading cause of death around the world and, thus, is a public health issue. The present scoping review aimed to update and summarize the available literature to detect specific environmental pollutants and their association with certain types of childhood cancer. Studies published from 2013 to 2023 regarding environmental pollution and childhood cancer were retrieved from the PubMed database. A total of 174 studies were eligible for this review and were analyzed. Our search strategy brought up most of the articles that evaluated air pollution (29%) and pesticides (28%). Indoor exposure to chemicals (11%), alcohol and tobacco use during pregnancy (16%), electromagnetic fields (12%), and radon (4%) were the subjects of less research. We found a particularly high percentage of positive associations between prenatal and postnatal exposure to indoor (84%) and outdoor (79%) air pollution, as well as to pesticides (82%), and childhood cancer. Positive associations were found between leukemia and pesticides and air pollution (33% and 27%); CNS tumors and neuroblastoma and pesticides (53% and 43%); and Wilms tumor and other rare cancers were found in association with air pollution (50%). Indoor air pollution was mostly reported in studies assessing several types of cancer (26%). Further studies are needed to investigate the mechanisms underlying the potential associations between indoor/outdoor air pollution and pesticide exposure with childhood cancer risk as more preventable measures could be taken.

Risk factors for childhood brain tumours: A systematic review and meta-analysis of observational studies from 1976 to 2022

BACKGROUND

Childhood brain tumours (CBTs) are the leading cause of cancer death in children under the age of 20 years globally. Though the aetiology of CBT remains poorly understood, it is thought to be multifactorial. We aimed to synthesize potential risk factors for CBT to inform primary prevention.

METHODS

We conducted a systematic review and meta-analysis of epidemiological studies indexed in the PubMed, Web of Science, and Embase databases from the start of those resources through 27 July 2023. We included data from case-control or cohort studies that reported effect estimates for each risk factor around the time of conception, during pregnancy and/or during post-natal period. Random effects meta-analysis was used to estimate summary effect sizes (ES) and 95% confidence intervals (CIs). We also quantified heterogeneity (I2) across studies.

FINDINGS

A total of 4040 studies were identified, of which 181 studies (85 case-control and 96 cohort studies) met our criteria for inclusion. Of all eligible studies, 50% (n = 91) were conducted in Europe, 32% (n = 57) in North America, 9% (n = 16) in Australia, 8% (n = 15) in Asia, 1% (n = 2) in South America, and none in Africa. We found associations for some modifiable risk factors including childhood domestic exposures to insecticides (ES 1.44, 95% CI 1.20-1.73) and herbicides (ES 2.38, 95% CI 1.31-4.33). Maternal domestic exposure to insecticides (ES 1.45, 95% CI 1.09-1.94), maternal consumption of cured meat (ES 1.51, 95% CI 1.05-2.17) and coffee ≥ 2 cups/day (ES 1.45, 95% 95% CI 1.07-1.95) during pregnancy, and maternal exposure to benzene (ES 2.22; 95% CI 1.01-4.88) before conception were associated with CBTs in case-control studies. Also, paternal occupational exposure to pesticides (ES 1.48, 95% CI 1.23-1.77) and benzene (ES 1.74, 95% CI 1.10-2.76) before conception and during pregnancy were associated in case-control studies and in combined analysis. On the other hand, assisted reproductive technology (ART) (ES 1.32, 95% CI 1.05-1.67), caesarean section (CS) (ES 1.12, 95% CI 1.01-1.25), paternal occupational exposure to paint before conception (ES 1.56, 95% CI 1.02-2.40) and maternal smoking > 10 cigarettes per day during pregnancy (ES 1.18, 95% CI 1.00-1.40) were associated with CBT in cohort studies. Maternal intake of vitamins and folic acid during pregnancy was inversely associated in cohort studies. Hormonal/infertility treatment, breastfeeding, child day-care attendance, maternal exposure to electric heated waterbed, tea and alcohol consumption during pregnancy were among those not associated with CBT in both case-control and cohort studies.

CONCLUSION

Our results should be interpreted with caution, especially as most associations between risk factors and CBT were discordant between cohort and case-control studies. At present, it is premature for any CBT to define specific primary prevention guidelines.

Racial and ethnic and socioeconomic disparities in childhood cancer incidence trends in the United States, 2000-2019

BACKGROUND

Population-based surveillance of pediatric cancer incidence trends is critical to determine high-risk populations, drive hypothesis generation, and uncover etiologic heterogeneity. We provide a comprehensive update to the current understanding of pediatric cancer incidence trends by sex, race and ethnicity, and socioeconomic status (SES).

METHODS

The Surveillance, Epidemiology, and End Results 22 data (2000-2019) was used to summarize age-adjusted incidence rates for children and adolescents aged 0-19 years at diagnosis. The annual percentage change (APC) and 95% confidence interval (CI) were estimated to evaluate incidence trends by sex, race and ethnicity, and SES overall and for cancer subtypes. Tests of statistical significance were 2-sided.

RESULTS

Substantial variation was observed overall and for several histologic types in race and ethnicity- and SES-specific rates. Overall, we observed a statistically significant increase in incidence rates (APC = 0.8%, 95% CI = 0.6% to 1.1%). All race and ethnic groups saw an increase in incidence rates, with the largest occurring among non-Hispanic American Indian and Alaska Native children and adolescents (APC = 1.7%, 95% CI = 0.5% to 2.8%) and the smallest increase occurring among non-Hispanic White children and adolescents (APC = 0.7%, 95% CI = 0.5% to 1.0%). The lowest SES quintiles saw statistically significant increasing trends, while the highest quintile remained relatively stable (quintile 1 [Q1] APC = 1.6%, 95% CI = 0.6% to 2.6%; quintile 5 [Q5] APC = 0.3%, 95% CI = -0.1% to 0.7%).

CONCLUSIONS

Childhood cancer incidence is increasing overall and among every race and ethnic group. Variation by race and ethnicity and SES may enable hypothesis generation on drivers of disparities observed.

Exploring Urban Green Spaces' Effect against Traffic Exposure on Childhood Leukaemia Incidence

BACKGROUND

Several environmental factors seem to be involved in childhood leukaemia incidence. Traffic exposure could increase the risk while urban green spaces (UGS) exposure could reduce it. However, there is no evidence how these two factors interact on this infant pathology.

OBJECTIVES

to evaluate how residential proximity to UGS could be an environmental protective factor against traffic exposure on childhood leukaemia incidence.

METHODS

A population-based case control study was conducted across thirty Spanish regions during the period 2000-2018. It included 2526 incident cases and 15,156, individually matched by sex, year-of-birth, and place-of-residence. Using the geographical coordinates of the participants' home residences, a 500 m proxy for exposure to UGS was built. Annual average daily traffic (AADT) was estimated for all types of roads 100 m near the children's residence. Odds ratios (ORs) and 95% confidence intervals (95% CIs), UGS, traffic exposure, and their possible interactions were calculated for overall childhood leukaemia, and the acute lymphoblastic (ALL) and acute myeloblastic leukaemia (AML) subtypes, with adjustment for socio-demographic covariates.

RESULTS

We found an increment of childhood leukaemia incidence related to traffic exposure, for every 100 AADT increase the incidence raised 1.1% (95% CI: 0.58-1.61%). UGS exposure showed an incidence reduction for the highest exposure level, Q5 (OR = 0.63; 95% CI = 0.54-0.72). Regression models with both traffic exposure and UGS exposure variables showed similar results but the interaction was not significant.

CONCLUSIONS

Despite their opposite effects on childhood leukaemia incidence individually, our results do not suggest a possible interaction between both exposures. This is the first study about the interaction of these two environmental factors; consequently, it is necessary to continue taking into account more individualized data and other possible environmental risk factors involved.

Occupational health risk assessment of the benzene exposure industries: a comprehensive scoring method through 4 health risk assessment models

Benzene is one of the most common occupational hazards in the working environment which was in the list of group 1 carcinogens. This study applied four occupational health risk assessment models: EPA model; MOM model of Singapore; the International Council on Mining and Metals (ICMM) model, and the Technical guide WS/T 777-2021 of China. The models assessed both non-carcinogenic and carcinogenic effects of benzene for 1629 employees in 50 factories in Jiangsu Province (China) who were exposed to benzene in the working environment and analysis the risk between industries by principal component analysis (PCA) method. The highest occupational health hazard of benzene among the five industries is petroleum processing industry, then followed by chemical products manufacturing industry, special equipment manufacturing industry, wood processing and products industry, and at last the pharmaceutical manufacturing industry. The population of abnormal routine blood parameters in the subjects was mostly in the "wood products industry" group, and the concentration of benzene in "wood products industry" group is the lowest in 5 groups. The industries with low exposure concentration have higher blood abnormality rates; this may be caused by the fact that blood damage is more secretive under low occupational health risk.

High expression of HIF-1α alleviates benzene-induced hematopoietic toxicity and immunosuppression in mice

Benzene exposure can cause pancytopenia and immunosuppression, leading to serious diseases such as aplastic anemia (AA) or acute myeloid leukemia (AML), but the underlying mechanism has not been fully elucidated. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that regulates many downstream target genes. In this study, we reported a novel mechanism by which high expression of HIF-1α alleviated benzene toxicity. Mice with high expression of HIF-1α (HIF-1α⁺) were obtained by the Tet-on system and doxycycline induction, and they and wild-type (WT) mice were exposed to 150 mg/kg benzene for 0, 1, 3, 7, 10, 14, and 28 days. Dynamic changes in hematopoietic and immune-related indicators and the role of HIF-1α were explored. The level of white blood cells in mice reached the highest level on the third day, and immunity was activated and then suppressed within 10 days. Significant pancytopenia and immunosuppression occurred at 14 days and were more pronounced at 28 days. The levels of HIF-1α, EPO, VEGF, RORγt, and IL-17 in WT mice gradually decreased with increasing benzene exposure days, while the levels of Foxp3 and IL-10 increased. These changes were alleviated in HIF-1α⁺ mice. High expression of HIF-1α increased the levels of EPO and VEGF, which helped to maintain the stability of the hematopoietic microenvironment. Simultaneously, it attenuated benzene-induced immunosuppression by alleviating the Th17/Treg imbalance. HIF-1α is expected to be a new target for benzene-induced diseases such as AA and AML.

Persistently high incidence rates of childhood acute leukemias from 2010 to 2017 in Mexico City: A population study from the MIGICCL

Introduction

Over the years, the Hispanic population living in the United States has consistently shown high incidence rates of childhood acute leukemias (AL). Similarly, high AL incidence was previously observed in Mexico City (MC). Here, we estimated the AL incidence rates among children under 15 years of age in MC during the period 2010-2017.

Methods

The Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia conducted a study gathering clinical and epidemiological information regarding children newly diagnosed with AL at public health institutions of MC. Crude age incidence rates (cAIR) were obtained. Age-standardized incidence rates worldwide (ASIRw) and by municipalities (ASIRm) were calculated by the direct and indirect methods, respectively. These were reported per million population <15 years of age; stratified by age group, sex, AL subtypes, immunophenotype and gene rearrangements.

Results

A total of 903 AL cases were registered. The ASIRw was 63.3 (cases per million) for AL, 53.1 for acute lymphoblastic leukemia (ALL), and 9.4 for acute myeloblastic leukemia. The highest cAIR for AL was observed in the age group between 1 and 4 years (male: 102.34 and female: 82.73). By immunophenotype, the ASIRw was 47.3 for B-cell and 3.7 for T-cell. The incidence did not show any significant trends during the study period. The ASIRm for ALL were 68.6, 66.6 and 62.8 at Iztacalco, Venustiano Carranza and Benito Juárez, respectively, whereas, other municipalities exhibited null values mainly for AML.

Conclusion

The ASIRw for childhood AL in MC is among the highest reported worldwide. We observed spatial heterogeneity of rates by municipalities. The elevated AL incidence observed in Mexican children may be explained by a combination of genetic background and exposure to environmental risk factors.

Residential road traffic and railway noise and risk of childhood cancer: A nationwide register-based case-control study in Denmark

BACKGROUND

The aetiology of most childhood cancers remains poorly understood. We conducted a nationwide register-based case-control study to assess the association between residential road traffic and railway noise exposure and risk of childhood cancers.

METHODS

We identified all cases of first cancers diagnosed in children aged 0-19 years in 1985-2013 from the Danish Cancer Registry (N = 3962) and sampled four individually matched (by sex and date of birth) controls per case (N = 14,790) using the Central Population Register. We estimated time-weighted exposure averages of residential road traffic and railway noise at the most (Lden max) and least (Lden min) exposed façades from birth to index-date (for additional analysis: in utero period) based on the individual address history for the respective time windows. We fitted conditional logistic regression models to estimate odds ratios (OR) and their 95% confidence intervals (CI).

RESULTS

ORs varied by noise estimate and cancer type, with generally wide CIs mostly including 1.00. We found a tendency of higher ORs with increasing railway and road traffic noise for Hodgkin lymphoma (ORs for railway and road Lden min were 1.63 (95% CI 1.00; 2.66) and 1.14 (95% CI 0.87; 1.48) per 10 dB), as well as a tendency of higher ORs with increasing railway noise for non-Hodgkin lymphoma. For embryonal CNS tumours and astrocytoma and other glioma we observed also some weak suggestions of a positive association. Analysing exposure to traffic noise in utero revealed similar patterns to those of the main analyses.

CONCLUSIONS

This nationwide study with minimal risk of bias suggests no strong associations between traffic noise and risk of most childhood cancers. We found however some suggestive evidence for a positive association with Hodgkin lymphoma, non-Hodgkin lymphoma and some CNS tumours. Further research is warranted to confirm these associations in other populations and elucidate the underlying biological mechanisms.

DNA damage, DNA repair gene expression, and topoisomerase IIα activity in CD-1 mice following in utero benzene exposure

Benzene is an environmental toxicant and known human carcinogen. Recent epidemiological studies show a relationship between exposure to benzene in pregnant women and increased incidence of childhood leukemias. Studies in murine models demonstrate a relationship between carcinogenicity and in utero benzene exposure which was sex dependent, thus the cellular mechanisms of benzene toxicity by sex require further studies. A hypothesized mechanism of benzene-induced in utero carcinogenicity is through increased DNA damage and reduced fetal DNA repair capacity. This includes the potential inhibition of topoisomerase IIα (topo IIα), in part, to generate double stranded DNA (dsDNA) breaks and induction of error-prone DNA repair. Using a mouse model of transplacental benzene carcinogenicity, gestational day (GD) 14 fetal livers were harvested 2, 6, and 24 h following maternal exposure to 200 mg/kg benzene and used to assess DNA damage, DNA repair gene expression and topo IIα activity. DNA damage, measured by levels of modified histone H2AX (γH2AX), is significantly increased in benzene exposed pups, with sex-dependent significance seen only in female pups. Comet assay results confirmed that benzene exposure in utero induces dsDNA damage in the GD14 fetal liver. Genes involved in DNA repair were assessed, and DNA repair gene expression changes were observed after 24 h in genes related to nucleotide excision repair, homologous recombination, and non-homologous end-joining. There were no significant differences in topo IIα activity in GD14 fetal livers at any timepoint, or between sexes. Overall, this study shows that 200 mg/kg benzene exposure induces dsDNA damage and alters fetal DNA repair gene expression in utero, without perturbing fetal topo IIα in CD-1 mice.

Childhood cancer and traffic-related air pollution in Switzerland: A nationwide census-based cohort study

Motor vehicle exhaust is a major contributor to air pollution, and exposure to benzene or other carcinogenic components may increase cancer risks. We aimed to investigate the association between traffic-related air pollution and risk of childhood cancer in a nationwide cohort study in Switzerland. We identified incident cases from the Swiss Childhood Cancer Registry diagnosed < 16 years of age between 1990 and 2015 and linked them probabilistically with the census-based Swiss National Cohort study. We developed land use regression models to estimate annual mean ambient levels of nitrogen dioxide (NO2) and benzene outside 1.4 million children's homes. We used risk-set sampling to facilitate the analysis of time-varying exposure and fitted conditional logistic regression models adjusting for neighborhood socio-economic position, level of urbanization, and background ionizing radiation. We included 2,960 cancer cases in the analyses. The adjusted hazard ratios (HR) and 95% confidence intervals for exposure to NO2 per 10 μg/m3 were 1.00 (95%-CI 0.88-1.13) for acute lymphoblastic leukemia (ALL) and 1.31 (95%-CI 1.00-1.71) for acute myeloid leukemia (AML). Using exposure lagged by 1 to 5 years instead of current exposure attenuated the effect for AML. The adjusted HR for exposure to benzene per 1 μg/m3 was 1.03 (95%-CI 0.86-1.23) for ALL and 1.29 (95%-CI 0.86-1.95) for AML. We also observed increased HRs for other diagnostic groups, notably non-Hodgkin lymphoma. Our study adds to the existing evidence that exposure to traffic-related air pollution is associated with an increased risk of childhood leukemia, particularly AML.

Childhood cancer and residential proximity to petrol stations: a nationwide registry-based case-control study in Switzerland and an updated meta-analysis

PURPOSE

Benzene is a known carcinogen for adult leukemia. Exposure to benzene through parental occupation and the use of household products has been associated with childhood leukemia (CL). Ambient benzene has also been associated with CL and central nervous system (CNS) tumors. We aimed to investigate whether the higher ambient levels of benzene in proximity of petrol stations are associated with a greater risk of childhood cancers, leukemia, and CNS tumors.

METHODS

We identified children diagnosed with cancer at age 0-15 years during 1985-2015 from the Swiss Childhood Cancer Registry and selected 10 age and sex-matched controls per case from national censuses. We calculated the distance from children's home to the nearest petrol station using precise geocodes. We estimated odds ratios using conditional logistic regression adjusting for ambient levels of NO₂, distance to highways, level of urbanization, and presence of a cantonal cancer registry. In addition, we ran a meta-analysis pooling current results for CL with those of previous studies.

RESULTS

We identified 6129 cases, of which 1880 were leukemias and 1290 CNS tumors. 24 cases lived within 50 m from a petrol station. The adjusted odds ratio of a cancer diagnosis for children thus exposed compared to unexposed children (> 500 m) was 1.29 (0.84-1.98) for all cancers combined, 1.08 (0.46-2.51) for leukemia, and 1.30 (0.51-3.35) for CNS tumors. During 2000-2015, when exposure assessment was more precise, the adjusted odds ratio for any cancer diagnosis was 1.77 (1.05-2.98). The summary relative risk estimate for CL in the meta-analysis including four studies was 2.01 (1.25-3.22).

CONCLUSIONS

Our study provides weak support for an increased risk of childhood cancers among children living close to petrol stations. A meta-analysis including our study suggests an increased risk for CL.

Environmental Risk Factors for Childhood Cancer in an Era of Global Climate Change: A Scoping Review

INTRODUCTION

Contemporary research about environmental risk factors in an era of global climate change to inform childhood cancer prevention efforts is disjointed. Planetary pediatric providers need to establish a better understanding of how the postnatal environment influences childhood cancer. Authors conducted a scoping review of recent scientific literature with the aim of understanding the environmental risk factors for childhood cancer.

METHOD

Ovid Medline, CINAHL, and Scopus databases were searched with results limited to the English language with publication years 2010-2021. Two independent reviewers screened 771 abstracts and excluded 659 abstracts and 65 full-text articles on the basis of predefinedcriteria.

RESULTS

The scoping review identified 47 studies about environmental risk factors for childhood cancer with mixed results and limited consensus in four main categories, including air pollution, chemical exposures, radiation, and residential location.

DISCUSSION

Research by collaborative international groups of planetary health researchers about environmental risk factors is needed to inform global health policy for childhood cancer prevention efforts.

Exposure to outdoor air pollution at different periods and the risk of leukemia: a meta-analysis

The causes of leukemia remain largely unknown; our aims were to examine the association between the exposure to outdoor air pollution and leukemia risk and to explore the effect of this exposure during different periods of pregnancy and early life. We searched for all case-control and cohort studies published before February 20, 2021, which measured the risk of leukemia in relation to exposure to the air pollutants: particulate matter, benzene, nitrogen dioxide (NO₂), and nitrogen oxides (NO_x). We then carried out a meta-analysis and calculated the summary relative risks (RRs) of leukemia by using a random-effects model. The potential dose-response relationship was further explored. The results showed that the highest exposure to benzene (RR: 1.20, 95%CI: 1.06-1.35) and NO₂ (RR: 1.04, 95%CI; 1.02-1.08) were positively correlated with leukemia risk when compared to the lowest exposure categories for each air pollutant. During pregnancy, exposure to benzene in the third trimester, as well as exposure to NO₂ in the second trimester and entire pregnancy, could also increase the risk of leukemia. In the dose-response analysis, benzene exposure and NO₂ exposure were linearly associated with the risk of leukemia. Other air pollutants did not have a statistical correlation with leukemia risk. There was a certain degree of publication bias in studies on benzene. Overall, our results support a link between outdoor air pollution and leukemia risk, particularly due to benzene and NO₂. Prospero Registration Number: PROSPERO CRD42020207025.

Individual and neighbourhood socioeconomic measures and the risk of non-central nervous system solid tumours in children: A nationwide register-based case-control study in Denmark

BACKGROUND

The aetiology for most solid tumours in childhood is largely unknown. The lack of evidence concerns also the relationship between socioeconomic position (SEP) and risk of childhood solid tumours other than in the central nervous system (CNS). We sought to access the association between individual and neighbourhood SEP measures and risk of childhood non-CNS solid tumours in Denmark and to evaluate whether associations varied by measure of SEP, time point of SEP assessment (during pregnancy versus before diagnosis) and tumour type.

METHODS

We conducted a nationwide case-control study based on Danish registry data. We identified all children born in 1980-2013 and diagnosed with a non-CNS solid tumour at ages 0-19 years (N = 1961) from the Danish Cancer Registry and sampled four individually matched controls per case using the Population Registry. We fitted conditional logistic regression models to estimate associations with register-based individual-level and neighbourhood-level SEP measures.

RESULTS

We observed a tendency of increased odd ratios (OR) in association with medium and high maternal income for most tumour types (e.g. OR for the highest income quintile and malignant bone tumours = 2.11; 95 % CI: 1.01, 4.38) and for parental education in association with higher education for some tumour types. For malignant epithelial neoplasms, higher parental education and income level were overall associated with an increased risk, e.g. OR = 1.63 (95 % CI: 1.00, 2.65) for the fourth group of maternal income during pregnancy. We found no risk pattern for neighbourhood SEP.

CONCLUSION

This large register-study with minimal risk of bias found a tendency of slightly to moderately increased risks for most childhood non-CNS solid tumours in association with higher maternal income and parental education. Future research examining the underlying mechanisms of these socioeconomic differences in non-CNS solid tumours as well as other childhood cancer types are warranted.

The Impacts of Illegal Toxic Waste Dumping on Children's Health: A Review and Case Study from Pasir Gudang, Malaysia

Poor management of hazardous waste can lead to environmental pollution, injuries, and adverse health risks. Children's exposure to hazardous waste may cause serious acute and chronic health problems due to their higher vulnerability to the toxic effects of chemicals. This study examines an incident of illegal chemical dumping in Pasir Gudang, Malaysia and its potential health impacts on children. The study introduced a risk assessment of possible health-related effects due to chemical contamination based on a real case scenario where quantification of the contamination was not feasible. A literature review and spatial analysis were used as research methods. On 6th March 2019, tons of hazardous waste were illegally disposed into Kim Kim River, Pasir Gudang, Malaysia. They were identified as benzene, acrolein, acrylonitrile, hydrogen chloride, methane, toluene, xylene, ethylbenzene, and d-limonene. As a result, 975 students in the vicinity developed signs and symptoms of respiratory disease due to the chemical poisoning. The findings of this study indicate that more effective policies and preventive actions are urgently needed to protect human health, especially children from improper hazardous waste management.

The role of residential history in cancer research: A scoping review

The role of residential history in cancer prevention, diagnosis, treatment, and survivorship is garnering increasing attention in cancer research. To our knowledge, there is no comprehensive synthesis of the current state of knowledge in the field. We reviewed the extant literature on this topic and conducted a scoping analysis to examine two main research questions: (a) To what degree, and how, have researchers accounted for residential history/mobility in cancer research? and (b) What are the gaps in the literature based on a knowledge synthesis using scoping review and concept mapping? To answer these questions, this scoping analysis focuses on how researchers compile, analyze and discuss residential history/mobility in studies on cancer. The study is focused on peer-reviewed articles from 6 different datasets (PubMed, Cinahl, Scopus, Web of Science and JSTOR, ERIC) from 1990 to August 2020. The review captured 1951 results in total, which was scoped to 281 relevant peer-reviewed journal articles. First, we examined these articles based on cancer continuum, cancer type and the main theme. Second, we identified 21 main themes and an additional 16 sub-themes in the pool of the selected articles. We utilized concept mapping to provide a conceptual framework and to highlight the underlying socioecological assumptions and paradigms. Results show that cancer research incorporating residential histories is primarily focused on incidence and estimating cumulative exposure, with little consideration across the cancer continuum. Additionally, our review suggests that although the social environment plays an important role across the cancer continuum, a small number of articles were focused on such factors and this area remains relatively unexplored. Additionally, the expansion of interdisciplinary research on residential mobility before and after cancer diagnosis will enhance understanding of the role of environmental and socioeconomic characteristics and exposures on cancer continuum.

Is the risk of childhood leukaemia associated with socioeconomic measures in Denmark? A nationwide register-based case-control study

The aetiology of childhood leukaemia is poorly understood. Knowledge about differences in risk by socioeconomic status (SES) may enhance etiologic insights. We conducted a nationwide register-based case-control study to evaluate socioeconomic differences in the risk of childhood leukaemia in Denmark and to access whether associations varied by different measures of SES, time point of assessment, leukaemia type and age at diagnosis. We identified all cases of leukaemia in children aged 0 to 19 years, born and diagnosed between 1980 and 2013 from the Danish Cancer Registry (N = 1336) and sampled four individually matched controls per case (N = 5330). We used conditional logistic regression models for analysis. Medium and high level of parental education was associated with a higher risk of acute myeloid leukaemia (AML) in the offspring, mainly driven by children diagnosed at ages 0 to 4 years [odds ratio (OR) for high maternal education = 3.07; 95% confidence interval (CI): 1.44-6.55]. We also observed a modestly increased risk for lymphoid leukaemia (LL) in association with higher level of parental education, but only in children diagnosed at ages 5 to 19 years. Higher parental income was associated with an increased risk of LL but not AML among children aged 5 to 19 years at diagnosis (OR for high maternal income = 2.78; 95% CI: 1.32-5.89). Results for neighbourhood SES measures indicated null associations. Bias or under-ascertainment of cases among families with low income or basic education are unlikely to explain the observed socioeconomic differences. Future research addressing explicitly the underlying mechanisms of our results may help to enhance etiologic insights of the disease.

Residential Exposure to PM2.5 Components and Risk of Childhood Non-Hodgkin Lymphoma in Denmark: A Nationwide Register-Based Case-Control Study

In a recent study, we observed an increased risk of childhood non-Hodgkin lymphoma (NHL) associated with exposure to fine atmospheric particulate matter (PM_2.5) and black carbon (BC). In this nationwide register-based case-control study, we focus on specific components of PM_2.5 in relation to childhood NHL in Denmark (1981–2013) by identifying all incidents of childhood NHL cases in the Danish Cancer Registry (n = 170) and four (cancer-free) randomly selected controls matched by date of birth and sex. We applied PM_2.5 concentrations and the following sub-components: secondary organic aerosols (SOA), secondary inorganic aerosols (SIA; i.e., NO₃⁻, NH₄⁺ and SO₄²⁻), BC, organic carbon (OC) and sea salt. We calculated a time-weighted exposure average from birth to index-date at all addresses. Odds ratios (ORs) were adjusted for register-based socio-demographic variables. We observed adjusted ORs and 95% confidence intervals (95% CI) of 2.05 (1.10, 3.83) per interquartile range (IQR, 4.83 µg/m³) PM_2.5 and 1.73 (0.68, 4.41) per IQR (3.71 µg/m³) SIA, 0.95 (0.71, 1.29) per IQR (0.05 µg/m³) SOA, 1.22 (1.02, 1.46) per IQR (0.39 µg/m³) BC, 1.02 (0.83, 1.26) per IQR (0.56 µg/m³) OC and 1.01 (0.79, 1.30) per IQR (0.87 µg/m3) sea salt, respectively. The estimates were attenuated after adjustment for PM_2.5, whereas the OR for PM_2.5 remained increased regardless of adjustment for specific components. The findings indicate that the previously observed relation between PM_2.5 and childhood NHL may be related to BC (as reported in our previous study) but also partly to SIA, but the role of specific chemical components of PM_2.5 remains ambiguous.

Global burden and trend of acute lymphoblastic leukemia from 1990 to 2017

Acute lymphoblastic leukemia (ALL) is a common malignant hematologic disease that is characterized by large numbers of dedifferentiated lymphoid cells. Statistical data of ALL's incidence and mortality are fundamental for policymakers to allocate resources optimally. In this study, we reported the incidence, death, and disability-adjusted life year (DALY) of ALL in the globe from 1990 to 2017. Our analysis showed that the incidence case of ALL increased by 30.81%, while the age-standardized incidence rate (ASIR) maintained stable. Subgroup analysis by social-demographic index (SDI) showed that ALL's ASIR was significantly decreased in high SDI countries, but were moderately increased in high-middle SDI countries. The change trends of age-standardized death rate and DALY rate were similar to ASIR trends. Subgroup analysis by age groups showed that children and the elderly were more likely to suffer ALL. Risk factor analysis demonstrated that smoking was the most significant contributor to ALL's death and DALY in the globe. Besides, the high body-mass index is playing an increasingly important role in ALL-caused mortality. Multiple methods to counteract potential risk factors should be adopted, such as controlling body-mass index in all regions and avoiding occupational exposure to carcinogens in low SDI countries.

Air pollution exposure at the residence and risk of childhood cancers in Denmark: A nationwide register-based case-control study

BACKGROUND

The etiology of childhood cancer is poorly understood. The role of environmental factors, including air pollution (AP) exposure, has been addressed previously, but results so far have been inconclusive. In this study, we investigate the association between long-term AP exposures in relation to childhood cancer subtypes in Denmark (1981-2013).

METHODS

We conducted a nationwide register-based case-control study. We identified 7745 incident cases of childhood cancers (<20 years) in the Danish Cancer Registry. Four randomly selected (cancer-free) controls were matched to each case according to sex and date of birth. We modelled concentrations of nitrogen dioxide (NO₂), fine particles (PM_2·5), and black carbon (BC) at all addresses and calculated a time-weighted average from birth to index-date with a state-of-the-art multiscale AP modelling system. We analyzed the risk of childhood cancer in conditional logistic regression models adjusted for socio-demographic variables obtained from registers at the individual and neighborhood level.

FINDINGS

The main analyses included 5045 cases and 18,179 controls. For all cancers combined, we observed odds ratios (ORs) and 95% confidence intervals (95% CI) of 0·97 (0·94, 1·01) per 10 µg/m³ NO₂, 0·89 (0·82, 0·98) per 5 µg/m³ PM_2·5, and 0·94 (0·88, 1·01) per 1 µg/m³ BC, respectively. Most notably, we observed a higher risk of Non-Hodgkin Lymphoma (NHL) with higher childhood AP exposure with ORs and 95% CIs of 1·21 (0·94, 1·55) per 10 µg/m³ NO₂, 2·11 (1·10, 4·01) per 5 µg/m³ PM_2·5, and 1·68 (1·06, 2·66) per 1 µg/m³ BC, respectively. We observed indications of increased risks for other types of childhood cancer, however, with very wide CIs including 1.

INTERPRETATIONS

The findings of this nation-wide study propose a role of AP in the development of childhood NHL, but more large-scale studies are needed.

FUNDING

NordForsk Project #75007.

Maternal exposure to pesticides and risk of childhood lymphoma in France: A pooled analysis of the ESCALE and ESTELLE studies (SFCE)

BACKGROUND

Few studies have assessed the relation between maternal prenatal pesticides use and childhood lymphoma risk, some reporting a positive association with non-Hodgkin lymphoma (NHL). We investigated the association between maternal exposure to pesticides during pregnancy and childhood Hodgkin (HL) and non-Hodgkin lymphoma.

METHODS

We pooled data from the two French national population-based case-control studies ESCALE (2003-2004) and ESTELLE (2010-2011). Data on domestic and occupational exposures to pesticides during pregnancy were obtained through standardised maternal interviews. Logistic regression models were used to compute odds ratios (OR) and 95% confidence intervals (CI) for HL and NHL, by pesticide category adjusted for potential confounders. Analyses by histological subtypes were also performed.

RESULTS

We included 328 H L, 305 non-Hodgkin NHL and 2,415 controls. Around 40% of control mothers reported having used pesticides during index pregnancy, of whom 95% reported insecticides use. Maternal use of herbicides and fungicides occurred mostly in combination with insecticides. Insecticides use was more frequently reported in cases than controls (OR_NHL = 1.6 [95%CI 1.3-2.1], p = 0.0001; OR_HL = 1.3 [95%CI 1.0-1.7], p = 0.03). This association appeared more marked for Burkitt lymphoma and mixed cellularity classical HL. No obvious association was observed with occupational pesticides exposure during pregnancy.

CONCLUSION

These results suggest that maternal domestic use of insecticides during pregnancy might be related to both childhood NHL and HL. Further larger studies are urgently needed.

Socioeconomic differences in the risk of childhood central nervous system tumors in Denmark: a nationwide register-based case-control study

PURPOSE

Differences in the risk of childhood central nervous system (CNS) tumors by socioeconomic status (SES) may enhance etiologic insights. We conducted a nationwide register-based case-control study to evaluate socioeconomic differences in the risk of childhood CNS tumors in Denmark and examined whether associations varied by different SES measures, time points of assessment, specific tumor types, and age at diagnosis.

METHODS

We identified all children born between 1981 and 2013 and diagnosed with a CNS tumor at ages 0-19 years (n = 1,273) from the Danish Cancer Registry and sampled four individually matched controls per case (n  = 5,086). We used conditional logistic regression models to estimate associations with individual-level and neighborhood-level socioeconomic measures.

RESULTS

We observed elevated risks of ependymoma and embryonal CNS tumors in association with higher parental education (odds ratios (ORs) of 1.6-2.1 for maternal or paternal high education and ependymoma) and higher risk of all tumor types in association with higher maternal income, e.g., OR  1.93; 95% CI 1.05-3.52 for high versus low income for astrocytoma and other gliomas. Associations were often stronger in children diagnosed at ages 5-19 years. We found little evidence for an association with neighborhood SES.

CONCLUSION

This large nationwide register study with minimal risk of bias showed that having parents with higher educational level and a mother with higher income was associated with a higher risk of childhood CNS tumors. Bias or under-ascertainment of cases among families with low income or basic education is unlikely to explain our findings.

Source apportionment of hourly-resolved ambient volatile organic compounds: Influence of temporal resolution

High temporal-resolution VOC concentration data can provide detailed and important temporal variations of VOC species and emission sources, which is not possible when using coarse temporal-resolution data. In this study, we utilized the positive matrix factorization (PMF) model to conduct source apportionment of hourly concentrations of nineteen VOC species and CO measured at the Mong Kok air quality monitoring station, operated by the Hong Kong Environmental Protection Department, from January 2013 to December 2014. The PMF analysis of the hourly dataset (PMF_Hourly) identified five sources, including liquefied petroleum gas (LPG) (contribution of 45%), gasoline exhaust (21%), combustion (20%), biogenic emission (9%), and paint solvents (6%). The diurnal patterns of VOC emissions from identified sources are likely to be affected by the strength of emissions, variation of the planetary boundary layer height, and photochemical reactions. In addition, the PMF analyses of hourly and 24-hour averaged data of the hourly-resolved data (PMF_Hourly and PMF_Daily) were generally comparable, but the time series of VOC emissions from PMF_Hourly could not be well captured by PMF_Daily for two local VOC sources of gasoline exhaust and LPG. This study highlights the benefit of high temporal-resolution measurement data in apportioning VOC sources, hence providing critical information on VOC emission sources (e.g., diurnal variations) for controlling VOC emissions effectively.

Epidemiology and Etiology of Leukemia and Lymphoma

Available evidence suggests that the incidence of leukemia and lymphoma tends to be higher in highly developed regions of the world and among Whites in the United States. Temporal trends in incidence are dynamic and multifactorial; for instance, the incidence of non-Hodgkin's lymphoma increased around the turn of the century, in part because of the acquired immune deficiency syndrome (AIDS) epidemic. Most leukemias and lymphomas are sporadic and the specific etiology remains elusive. Still, research shows that these malignancies often develop in the context of genetic abnormalities, immunosuppression, and exposure to risk factors like ionizing radiation, carcinogenic chemicals, and oncogenic viruses. The prognosis varies by subtype, with poorer survival outcomes for acute leukemias among adults, and more favorable outcomes for Hodgkin's lymphoma. At a time when specific prevention efforts targeting these malignancies are nonexistent, there is a great need to ensure equitable access to diagnostic services and treatments worldwide.

Long-term exposure to air pollution and risk of non-Hodgkin lymphoma in Denmark: A population-based case-control study

There is limited evidence regarding a possible association between exposure to ambient air pollutants and the risk of non-Hodgkin lymphoma (NHL). Previous epidemiological studies have relied on crude estimations for air pollution exposure and/or small numbers of NHL cases. The objective of our study was to analyze this association based on air pollution modeled at the address level and NHL cases identified from the nationwide Danish Cancer Registry. We identified 20,874 incident NHL cases diagnosed between 1989 and 2014 and randomly selected 41,749 controls matched on age and gender among the entire Danish population. We used conditional logistic regression to estimate odds ratios (ORs) and adjusted for individual and neighborhood level sociodemographic variables. There was no association between exposure to PM_2.5 , BC, O₃ , SO₂ or NO₂ and overall risk of NHL but several air pollutants were associated with higher risk of follicular lymphoma, but statistically insignificant, for example, PM_2.5 (OR = 1.15 per 5 μg/m³ ; 95% CI: 0.98-1.34) and lower risk for diffuse large B-cell lymphoma (OR = 0.92 per 5 μg/m³ ; 95% CI: 0.82-1.03). In this population-based study, we did not observe any convincing evidence of a higher overall risk for NHL with higher exposure to ambient air pollutants.

Parental tobacco smoking and risk of childhood leukemia in Costa Rica: A population-based case-control study

INTRODUCTION

The role of environmental and behavioral exposures on childhood leukemia etiology is poorly understood. We examined the association of maternal and paternal tobacco smoking at different time points with the risk of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) in Costa Rican children.

MATERIALS AND METHODS

We conducted a population-based case-control study on childhood leukemia in Costa Rica. Cases (n ALL = 252; n AML = 40) were diagnosed between 1995 and 2000 (aged <15 years at diagnosis) and identified from the Costa Rican Cancer Registry and the National Children's Hospital. A total of 578 frequency-matched population controls were sampled from the National Birth Registry. Parental tobacco smoking was assessed via face-to-face interviews. We used logistic regression models to examine the association of paternal and maternal tobacco smoking before conception, during pregnancy, and after birth with childhood ALL and AML risk, adjusted for child sex, birth year, maternal/paternal age, and parental education.

RESULTS

Paternal smoking before conception, during pregnancy, and after birth was associated with an increased risk of childhood AML (Odds Ratio (OR): 2.51, 95% CI: 1.21-5.17; OR: 3.21, 95% CI: 1.56-6.60; and OR: 2.83, 95% CI: 1.36-5.90, respectively). Maternal smoking during pregnancy was also associated with a modest, but imprecise increase in AML risk. We observed null associations of maternal and paternal smoking with ALL in the offspring.

CONCLUSION

Our results suggest an association between parental smoking and risk of AML, but not ALL, in Costa Rican children. These findings add to the established evidence of numerous health risks associated with smoking and highlight the potential harm of smoking during sensitive windows of the development of fetus and child.

Exosomal miR-221 derived from hydroquinone-transformed malignant human bronchial epithelial cells is involved in cell viability of recipient cells

miR-221, an oncogenic microRNA, can promote cell proliferation and is highly expressed in various types of tumors. However, the role of exosomal miR-221 in benzene-caused carcinogenesis remains elusive. Our study was designed to investigate whether exosomes secreted by the hydroquinone (HQ; an active metabolite of benzene)-transformed malignant cells can transmit miR-221 to normal recipient cells and its possible effects on cell viability. Our investigation revealed that expression levels of miR-221 were significantly increased in HQ-transformed malignant cells relative to normal controls. Furthermore, exposure of control cells to exosomes that were derived from HQ-transformed malignant cells increased miR-221 levels and promoted their proliferation. Analyses of the biological potency of exosomes derived from HQ-transformed malignant cells in which miR-221 levels were decreased using an inhibitor, showed that both miR-221 levels and proliferation of recipient cells were decreased, but still were higher than those of normal 16HBE cells. Our study indicates that exosomal miR-221 derived from HQ-transformed malignant human bronchial epithelial cells is involved in the proliferation of recipient cells.

Hierarchical Nanoheterostructure of Tungsten Disulfide Nanoflowers Doped with Zinc Oxide Hollow Spheres: Benzene Gas Sensing Properties and First-Principles Study

This paper reports an original fabrication of a benzene gas sensor based on tungsten disulfide nanoflowers (WS₂ NFs)/zinc oxide hollow spheres (ZnO HMDs) hierarchical nanoheterostructure. The ZnO/WS₂ hierarchical composite was characterized for the inspection of its nanostructure, elementary composition, and surface morphology. The benzene-sensing properties of the ZnO/WS₂ nanofilm sensor were exactly investigated. The results illustrate that the ZnO/WS₂ sensor exhibits a remarkable sensing performance toward benzene gas, including good sensitivity, rapid detection, outstanding repeatability, and stability. This is attributed to the fact that the ZnO/WS₂ nanoheterostructure can dramatically enhance the benzene sensing performance. Furthermore, density functional theory was employed to construct the benzene gas adsorption model for the ZnO/WS₂ heterostructure, from which the determined parameters in geometry, energy, and charge provided a powerful support for the mechanism explanation. This work suggests that the ZnO/WS₂ nanoheterostructure is competent to detect trace benzene gas at room temperature.

Methodological approaches to the study of cancer risk in the vicinity of pollution sources: the experience of a population-based case-control study of childhood cancer

Background

Environmental exposures are related to the risk of some types of cancer, and children are the most vulnerable group of people. This study seeks to present the methodological approaches used in the papers of our group about risk of childhood cancers in the vicinity of pollution sources (industrial and urban sites). A population-based case–control study of incident childhood cancers in Spain and their relationship with residential proximity to industrial and urban areas was designed. Two methodological approaches using mixed multiple unconditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) were developed: (a) “near vs. far” analysis, where possible excess risks of cancers in children living near (“near”) versus those living far (“far”) from industrial and urban areas were assessed; and (b) “risk gradient” analysis, where the risk gradient in the vicinity of industries was assessed. For each one of the two approaches, three strategies of analysis were implemented: “joint”, “stratified”, and “individualized” analysis. Incident cases were obtained from the Spanish Registry of Childhood Cancer (between 1996 and 2011).

Results

Applying this methodology, associations between proximity (≤ 2 km) to specific industrial and urban zones and risk (OR; 95% CI) of leukemias (1.31; 1.04–1.65 for industrial areas, and 1.28; 1.00–1.53 for urban areas), neuroblastoma (2.12; 1.18–3.83 for both industrial and urban areas), and renal (2.02; 1.16–3.52 for industrial areas) and bone (4.02; 1.73–9.34 for urban areas) tumors have been suggested.

Conclusions

The two methodological approaches were used as a very useful and flexible tool to analyze the excess risk of childhood cancers in the vicinity of industrial and urban areas, which can be extrapolated and generalized to other cancers and chronic diseases, and adapted to other types of pollution sources.

Association between Outdoor Air Pollution and Childhood Leukemia: A Systematic Review and Dose-Response Meta-Analysis

BACKGROUND

A causal link between outdoor air pollution and childhood leukemia has been proposed, but some older studies suffer from methodological drawbacks. To the best of our knowledge, no systematic reviews have summarized the most recently published evidence and no analyses have examined the dose-response relation.

OBJECTIVE

We investigated the extent to which outdoor air pollution, especially as resulting from traffic-related contaminants, affects the risk of childhood leukemia.

METHODS

We searched all case-control and cohort studies that have investigated the risk of childhood leukemia in relation to exposure either to motorized traffic and related contaminants, based on various traffic-related metrics (number of vehicles in the closest roads, road density, and distance from major roads), or to measured or modeled levels of air contaminants such as benzene, nitrogen dioxide, 1,3-butadiene, and particulate matter. We carried out a meta-analysis of all eligible studies, including nine studies published since the last systematic review and, when possible, we fit a dose-response curve using a restricted cubic spline regression model.

RESULTS

We found 29 studies eligible to be included in our review. In the dose-response analysis, we found little association between disease risk and traffic indicators near the child's residence for most of the exposure range, with an indication of a possible excess risk only at the highest levels. In contrast, benzene exposure was positively and approximately linearly associated with risk of childhood leukemia, particularly for acute myeloid leukemia, among children under 6 y of age, and when exposure assessment at the time of diagnosis was used. Exposure to nitrogen dioxide showed little association with leukemia risk except at the highest levels.

DISCUSSION

Overall, the epidemiologic literature appears to support an association between benzene and childhood leukemia risk, with no indication of any threshold effect. A role for other measured and unmeasured pollutants from motorized traffic is also possible. https://doi.org/10.1289/EHP4381.

Parental age and the risk of childhood acute myeloid leukemia: results from the Childhood Leukemia International Consortium

BACKGROUND

Parental age has been associated with several childhood cancers, albeit the evidence is still inconsistent.

AIM

To examine the associations of parental age at birth with acute myeloid leukemia (AML) among children aged 0-14 years using individual-level data from the Childhood Leukemia International Consortium (CLIC) and non-CLIC studies.

MATERIAL/METHODS

We analyzed data of 3182 incident AML cases and 8377 controls from 17 studies [seven registry-based case-control (RCC) studies and ten questionnaire-based case-control (QCC) studies]. AML risk in association with parental age was calculated using multiple logistic regression, meta-analyses, and pooled-effect estimates. Models were stratified by age at diagnosis (infants <1 year-old vs. children 1-14 years-old) and by study design, using five-year parental age increments and controlling for sex, ethnicity, birthweight, prematurity, multiple gestation, birth order, maternal smoking and education, age at diagnosis (cases aged 1-14 years), and recruitment time period.

RESULTS

Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) derived from RCC, but not from the QCC, studies showed a higher AML risk for infants of mothers ≥40-year-old (OR = 6.87; 95% CI: 2.12-22.25). There were no associations observed between any other maternal or paternal age group and AML risk for children older than one year.

CONCLUSIONS

An increased risk of infant AML with advanced maternal age was found using data from RCC, but not from QCC studies; no parental age-AML associations were observed for older children.