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Liu Y.,Huazhong University of Science and Technology | Liu Y.,Institute of Health Surveillance | Xi P.,National Research Council Canada | Joseph M.,U.S. National Institute for Occupational Safety and Health | And 5 more authors.
Annals of Occupational Hygiene | Year: 2014

This study aims to elucidate variations in head-and-face shape among the Chinese civilian workers. Most respirator manufacturers are using outdated, Western anthropometric data to design respirators for the Chinese workers. Therefore, newly acquired anthropometric data specific to the Chinese population are needed to create more effective personal protective equipment. The three-dimensional (3D) head scans of 350 participants, who were selected from the 3000 participants in the 2006 Chinese Anthropometric Survey, were processed using geometric processing techniques. Each scan was then linked with the others, making statistical shape analysis on a dense set of 3D points possible. Furthermore, this provided for the reduction of scan noise as well as for the patching of holes. Following general scan correspondence and fine tuning, principal component analysis was used to analyze the variability in head-and-face shape of the 3D images. More than 90% of the variability among head-and-face shapes was accounted for with 26 principal components. Future study is recommended so the overall usefulness of the point cloud-based approach for the quantification of variations in facial morphology may be determined. © 2015 The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Liu Y.,Key Laboratory of Environment and Health | Liu Y.,Institute of Health Surveillance | Rong Y.,Key Laboratory of Environment and Health | Steenland K.,Emory University | And 4 more authors.
Epidemiology | Year: 2014

BACKGROUND: The association between crystalline silica exposure and risk of heart disease mortality remains less clear. METHODS: We investigated a cohort of 42,572 Chinese workers who were potentially exposed to crystalline silica and followed from 1960 to 2003. Cumulative silica exposure was estimated by linking a job-exposure matrix to each person's work history. Low-level silica exposure was defined as never having held a job with an exposure higher than 0.1 mg/m. We estimated hazard ratios (HRs) in exposure-response analyses using Cox proportional hazards model. RESULTS: We identified 2846 deaths from heart disease during an average of 35 years follow-up. Positive exposure-response trends were observed for cumulative silica exposure associated with mortality from total heart disease (HRs for increasing quartiles of cumulative silica exposure compared with the unexposed group = 0.89, 1.09, 1.32, 2.10; P for linear trend < 0.001) and pulmonary heart disease (0.92, 1.39, 2.47, 5.46; P for linear trend < 0.001). These positive trends remained among workers with both high- and low-level silica exposure. There was also a positive trend for ischemic heart disease among workers with low-level exposure, with quartile HRs of 1.04, 1.13, 1.52, and 1.60 (P for linear trend < 0.001). CONCLUSION: Low-level crystalline silica exposure was associated with increased mortality from heart disease, including pulmonary heart disease and ischemic heart disease, whereas high-level exposure mainly increased mortality from pulmonary heart disease. Current permissible exposure limits for crystalline silica in many countries may be insufficient to protect people from deaths due to heart disease. Copyright © 2014 by Lippincott Williams & Wilkins.

Liu Y.,Institute of Health Surveillance | Liu Y.,U.S. National Institute for Occupational Safety and Health | Beaucham C.C.,U.S. National Institute for Occupational Safety and Health | Pearce T.A.,URS Corporation | Zhuang Z.,U.S. National Institute for Occupational Safety and Health
PLoS ONE | Year: 2014

Background: Nanoparticle emission assessment technique was developed to semi-quantitatively evaluate nanomaterial exposures and employs a combination of filter based samples and portable real-time particle monitors, including a condensation particle counter (CPC) and an optical particle counter (OPC), to detect nanomaterial releases. This laboratory study evaluated the results from CPC and OPC simultaneously measuring a polydisperse aerosol to assess their variability and accuracy. Methods and Results: Two CPCs and two OPCs were used to evaluate a polydisperse sodium chloride aerosol within an enclosed chamber. The measurement results for number concentration versus time were compared between paired particle monitors of the same type, and to results from the Scanning Mobility Particle Spectrometer (SMPS) which was widely used to measure concentration of size-specific particles. According to analyses by using the Bland-Altman method, the CPCs displayed a constant mean percent difference of -3.8% (95% agreement limits: -9.1 to 1.6%; range of 95% agreement limit: 10.7%) with the chamber particle concentration below its dynamic upper limit (100,000 particles per cubic centimeter). The mean percent difference increased from -3.4% to -12.0% (range of 95% agreement limits: 7.1%) with increasing particle concentrations that were above the dynamic upper limit. The OPC results showed the percent difference within 15% for measurements in particles with size ranges of 300 to 500 and 500 to 1000 regardless of the particle concentration. Compared with SMPS measurements, the CPC gave a mean percent difference of 22.9% (95% agreement limits: 10.5% to 35.2%); whereas the measurements from OPC were not comparable. Conclusions: This study demonstrated that CPC and OPC are useful for measuring nanoparticle exposures but the results from an individual monitor should be interpreted based upon the instrument's technical parameters. Future research should challenge these monitors with particles of different sizes, shapes, or composition, to determine measurement comparability and accuracy across various workplace nanomaterials. © 2014 Liu et al.

Zhuang Z.,U.S. National Institute for Occupational Safety and Health | Liu Y.,U.S. National Institute for Occupational Safety and Health | Liu Y.,Institute of Health Surveillance | Coffey C.C.,U.S. National Institute for Occupational Safety and Health | And 2 more authors.
Journal of Occupational and Environmental Hygiene | Year: 2015

Inter-panel variability has never been investigated. The objective of this study was to determine the variability between different anthropometric panels used to determine the inward leakage (IL) of N95 filtering facepiece respirators (FFRs) and elastomeric half-mask respirators (EHRs). A total of 144 subjects, who were both experienced and non-experienced N95 FFR users, were recruited. Five N95 FFRs and five N95 EHRs were randomly selected from among those models tested previously in our laboratory. The PortaCount Pro+ (without N95-Companion) was used to measure IL of the ambient particles with a detectable size range of 0.02 to 1 ìm. The Occupational Safety and Health Administration standard fit test exercises were used for this study. IL test were performed for each subject using each of the 10 respirators. Each respirator/subject combination was tested in duplicate, resulting in a total 20 IL tests for each subject. Three 35-member panels were randomly selected without replacement from the 144 study subjects stratified by the National Institute for Occupational Safety and Health bivariate panel cell for conducting statistical analyses. The geometric mean (GM)IL values for all 10 studied respirators were not significantly different among the three randomly selected 35-member panels. Passing rate was not significantly different among the three panels for all respirators combined or by each model. This was true for all IL pass/fail levels of 1%, 2%, and 5%.Using 26 or more subjects to pass the IL test, all three panels had consistent passing/failing results for pass/fail levels of 1% and 5%. Some disagreement was observed for the 2% pass/fail level. Inter-panel variability exists, but it is small relative to the other sources of variation in fit testing data. The concern about inter-panel variability and other types of variability can be alleviated by properly selecting: pass/fail level (IL 1-5%); panel size (e.g., 25 or 35); and minimum number of subjects required to pass (e.g., 26 of 35 or 23 of 35). Copyright © 2015 JOEH, LLC.

Liu Y.,Huazhong University of Science and Technology | Liu Y.,Institute of Health Surveillance | Steenland K.,Key Laboratory of Environment and Health | Steenland K.,Emory University | And 8 more authors.
American Journal of Epidemiology | Year: 2013

Crystalline silica has been classified as a human carcinogen by the International Agency for Research on Cancer (Lyon, France); however, few previous studies have provided quantitative data on silica exposure, silicosis, and/or smoking. We investigated a cohort in China (in 1960-2003) of 34,018 workers without exposure to carcinogenic confounders. Cumulative silica exposure was estimated by linking a job-exposure matrix to work history. Cox proportional hazards model was used to conduct exposure-response analysis and risk assessment. During a mean 34.5-year follow-up, 546 lung cancer deaths were identified. Categorical analyses by quartiles of cumulative silica exposure (using a 25-year lag) yielded hazard ratios of 1.26, 1.54, 1.68, and 1.70, respectively, compared with the unexposed group. Monotonic exposure-response trends were observed among nonsilicotics (P for trend < 0.001). Analyses using splines showed similar trends. The joint effect of silica and smoking was more than additive and close to multiplicative. For workers exposed from ages 20 to 65 years at 0.1 mg/m3 of silica exposure, the estimated excess lifetime risk (through age 75 years) was 0.51%. These findings confirm silica as a human carcinogen and suggest that current exposure limits in many countries might be insufficient to protect workers from lung cancer. They also indicate that smoking cessation could help reduce lung cancer risk for silica-exposed individuals. © The Author 2013.

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