Commercial use of carbon nanotubes and nanofibers (CNT/F) in composites and electronics is increasing; however, little is known about health effects among workers. We conducted a cross-sectional ...study among 108 workers at 12 U.S. CNT/F facilities. We evaluated chest symptoms or respiratory allergies since starting work with CNT/F, lung function, resting blood pressure (BP), resting heart rate (RHR), and complete blood count (CBC) components.
We conducted multi-day, full-shift sampling to measure background-corrected elemental carbon (EC) and CNT/F structure count concentrations, and collected induced sputum to measure CNT/F in the respiratory tract. We measured (nonspecific) fine and ultrafine particulate matter mass and count concentrations. Concurrently, we conducted physical examinations, BP measurement, and spirometry, and collected whole blood. We evaluated associations between exposures and health measures, adjusting for confounders related to lifestyle and other occupational exposures.
CNT/F air concentrations were generally low, while 18% of participants had evidence of CNT/F in sputum. Respiratory allergy development was positively associated with inhalable EC (p=0.040) and number of years worked with CNT/F (p=0.008). No exposures were associated with spirometry-based metrics or pulmonary symptoms, nor were CNT/F-specific metrics related to BP or most CBC components. Systolic BP was positively associated with fine particulate matter (p-values: 0.015-0.054). RHR was positively associated with EC, at both the respirable (p=0.0074) and inhalable (p=0.0026) size fractions. Hematocrit was positively associated with the log of CNT/F structure counts (p=0.043).
Most health measures were not associated with CNT/F. The positive associations between CNT/F exposure and respiratory allergies, RHR, and hematocrit counts may not be causal and require examination in other studies.
Low-dose, penetrating photon radiation exposure is ubiquitous, yet our understanding of cancer risk at low doses and dose rates derives mainly from high-dose studies. Although a large number of ...low-dose cancer studies have been recently published, concern exists about the potential for confounding to distort findings. The aim of this study was to describe and assess the likely impact of confounding and selection bias within the context of a systematic review.
We summarized confounding control methods for 26 studies published from 2006 to 2017 by exposure setting (environmental, medical, or occupational) and identified confounders of potential concern. We used information from these and related studies to assess evidence for confounding and selection bias. For factors in which direct or indirect evidence of confounding was lacking for certain studies, we used a theoretical adjustment to determine whether uncontrolled confounding was likely to have affected the results.
For medical studies of childhood cancers, confounding by indication (CBI) was the main concern. Lifestyle-related factors were of primary concern for environmental and medical studies of adult cancers and for occupational studies. For occupational studies, other workplace exposures and healthy worker survivor bias were additionally of interest. For most of these factors, however, review of the direct and indirect evidence suggested that confounding was minimal. One study showed evidence of selection bias, and three occupational studies did not adjust for lifestyle or healthy worker survivor bias correlates. Theoretical adjustment for three factors (smoking and asbestos in occupational studies and CBI in childhood cancer studies) demonstrated that these were unlikely to explain positive study findings due to the rarity of exposure (eg, CBI) or the relatively weak association with the outcome (eg, smoking or asbestos and all cancers).
Confounding and selection bias are unlikely to explain the findings from most low-dose radiation epidemiology studies.
Multi-walled carbon nanotubes and nanofibers (CNT/F) have been previously investigated for their potential toxicities; however, comparative studies of the broad material class are lacking, especially ...those with a larger diameter. Additionally, computational modeling correlating physicochemical characteristics and toxicity outcomes have been infrequently employed, and it is unclear if all CNT/F confer similar toxicity, including histopathology changes such as pulmonary fibrosis. Male C57BL/6 mice were exposed to 40 µg of one of nine CNT/F (MW #1-7 and CNF #1-2) commonly found in exposure assessment studies of U.S. facilities with diameters ranging from 6 to 150 nm. Human fibroblasts (0-20 µg/ml) were used to assess the predictive value of in vitro to in vivo modeling systems.
All materials induced histopathology changes, although the types and magnitude of the changes varied. In general, the larger diameter MWs (MW #5-7, including Mitsui-7) and CNF #1 induced greater histopathology changes compared to MW #1 and #3 while MW #4 and CNF #2 were intermediate in effect. Differences in individual alveolar or bronchiolar outcomes and severity correlated with physical dimensions and how the materials agglomerated. Human fibroblast monocultures were found to be insufficient to fully replicate in vivo fibrosis outcomes suggesting in vitro predictive potential depends upon more advanced cell culture in vitro models. Pleural penetrations were observed more consistently in CNT/F with larger lengths and diameters.
Physicochemical characteristics, notably nominal CNT/F dimension and agglomerate size, predicted histopathologic changes and enabled grouping of materials by their toxicity profiles. Particles of greater nominal tube length were generally associated with increased severity of histopathology outcomes. Larger particle lengths and agglomerates were associated with more severe bronchi/bronchiolar outcomes. Spherical agglomerated particles of smaller nominal tube dimension were linked to granulomatous inflammation while a mixture of smaller and larger dimensional CNT/F resulted in more severe alveolar injury.
In February–March, 2023, a Working Group of 20 scientists from 10 countries met at the invitation of the International Agency for Research on Cancer (IARC) in Lyon, France, to finalise their ...evaluation of the carcinogenicity of four agents: anthracene, 2-bromopropane, butyl methacrylate (BMA), and dimethyl hydrogen phosphite (DMHP). Multiple studies showed that 2-bromopropane induced DNA damage in human leukocytes, micronucleus formation in rodents, and gene mutations in bacteria. Monograph Working Group Members RC Cattley (USA)–Meeting Chair; H Kromhout (The Netherlands); M Sun (USA); EJ Tokar (USA) –Subgroup Meeting Chairs; MA-E Abdallah (UK); AK Bauer (USA); KR Broadwater (USA); L Campo (Italy); E Corsini (Italy); KA Houck (USA); G Ichihara (Japan); M Matsumoto (Japan); S Morais (Portugal); J Mráz (Czechia); T Nomiyama (Japan); K Ryan (USA); H Shen (People's Republic of China); T Toyoda (Japan); KH Vähäkangas (Finland); MG Yakubovskaya (Russian Federation) Declaration of interests All Working Group members declare no competing interests Invited Specialists IJ Je Yu, Hyundai Calibration & Certification Technologies Co Ltd, Republic of Korea Declaration of interests IJY reports being an employee of HCT Co., Ltd., a former spin-off of Hyundai Electronics, whose work may involve competing interests for the topics covered at this IARC Monographs meeting Representatives C Dellavalle, National Cancer Institute, USA Declaration of interests CD declares no competing interest Observers G Tuschl, Methacrylate REACH Task Force (MRTF), Germany Declaration of interests GT is employed with Rohm GmbH, manufacturer of butyl methacrylate.
RADON IN US WORKPLACES: A REVIEW Daniels, Robert D; Schubauer-Berigan, Mary K
Radiation protection dosimetry,
2017-Nov-01, 2017-11-01, 20171101, Volume:
176, Issue:
3
Journal Article
Peer reviewed
Open access
Exposure to naturally occurring radon is unavoidable and is second only to smoking as a direct cause of lung cancer in the USA. The literature for existing information on US occupations that are ...prone to increased radon exposures was reviewed. Current recommendations and applicable protective standards against occupational radon exposure that are applicable to US workers are discussed. Exposure varied widely among several working populations, most of whom were employed in industries that were unrelated to the uranium fuel cycle. Radon protection standards differed among agencies and have not changed since the height of domestic uranium production in the 1970s. In contrast, European countries are adopting recommendations by the International Commission on Radiation Protection to set a reference level near a derived annual exposure of about one working level month, which is 25% of the level currently established for US miners.
In March, 2022, a Working Group of 31 scientists from 13 countries met remotely at the invitation of the International Agency for Research on Cancer (IARC) to finalise their evaluation of the ...carcinogenicity of nine agents: cobalt metal (without tungsten carbide or other metal alloys), soluble cobalt(II) salts, cobalt(II) oxide, cobalt(II,III) oxide, cobalt(II) sulfide, other cobalt(II) compounds, trivalent antimony, pentavalent antimony, and weapons-grade tungsten (with nickel and cobalt) alloy. In two Good Laboratory Practice (GLP) studies2 in mice and rats, inhaled cobalt metal caused bronchioloalveolar carcinoma in male and female mice; bronchioloalveolar carcinoma, and malignant pheochromocytoma of the adrenal medulla in male and female rats; pancreatic islet carcinoma in male rats; and leukaemia in female rats. In two GLP studies in mice and rats, inhaled cobalt(II) sulfate caused bronchioloalveolar carcinoma in male and female mice; bronchioloalveolar tumours in male rats; and bronchioloalveolar carcinoma, and adrenal medulla tumours in female rats. In two GLP studies6 in rodents, inhalation exposure caused bronchioloalveolar carcinoma in male and female mice; fibrous histiocytoma and fibrosarcoma of the skin in male mice; lymphoma in female mice; and lung and adrenal medulla tumours in female rats.
Epidemiological studies of occupational, medical, and environmental exposures have provided important information on lung cancer risk and how those risks might depend on the type of exposure, dose ...rate, and other potential modifying factors such as sex and age of the exposed. Analyses of data from underground miner cohorts and residential case-control studies provide convincing evidence that radon is a leading cause of lung cancer. For low-LET radiation, risk models derived from results from the Lifespan Study of Japanese atomic bomb survivors suggest that for acute exposures, lifetime attributable risks for lung cancer are greater than for other specific cancer sites and are substantially larger for females than males. However, for protracted and fractionated exposures other than from radon, results from epidemiological studies are seemingly often contradictory.This report includes summaries of oral presentations during a symposium on radiogenic lung cancer risk given by a panel of experts on October 5 during the Radiation Research Society’s 67th annual meeting. This session included presentations on: 1) the largest pooled study of male uranium miners (PUMA) exposed to radon; 2) the most recent analysis of the Canadian Fluoroscopy cohort featuring state-of-the-art dosimetry for radiation exposures associated with frequent medical diagnostic procedures; 3) an update from the Million Person Study on risks from fractionated occupational exposures, and 4) studies of second primary malignancies – including lung cancer – in patients who had been treated for thyroid cancer.
The carcinogenicity of opium consumption was recently evaluated by a Working Group convened by the International Agency for Research on Cancer (IARC). We supplement the recent IARC evaluation by ...conducting an extended systematic review as well as a quantitative meta-analytic assessment of the role of opium consumption and risk for selected cancers, evaluating in detail various aspects of study quality on meta-analytic findings. We searched the published literature to identify all relevant studies on opium consumption and risk of selected cancers in humans through 31 October, 2022. Meta-relative risks (mRRs) and associated 95% confidence intervals (CIs) were estimated using random-effects models for studies of cancer of the urinary bladder, larynx, lung, oesophagus, pancreas, and stomach. Heterogeneity among studies was assessed using the
I
2
statistic. We assessed study quality and conducted sensitivity analyses to evaluate the impact of potential reverse causation, protopathic bias, selection bias, information bias, and confounding. In total, 2 prospective cohort studies and 33 case–control studies were included. The overall pooled mRR estimated for ‘
ever or regular
’ versus ‘
never
’ use of opium ranged from 1.50 (95% CI 1.13–1.99,
I
2
= 0%, 6 studies) for oesophageal cancer to 7.97 (95% CI 4.79–13.3,
I
2
= 62%, 7 studies) for laryngeal cancer. Analyses of cumulative opium exposure suggested greater risk of cancer associated with higher opium consumption. Findings were robust in sensitivity analyses excluding studies prone to potential methodological sources of biases and confounding. Findings support an adverse association between opium consumption and cancers of the urinary bladder, larynx, lung, oesophagus, pancreas and stomach.
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