Human exposure to carbon-based fibrous nanomaterials: A review.

In an emerging field of nanotechnologies, assessment of exposure to carbon nanotubes (CNT) and carbon nanofibers (CNF) is an integral component of occupational and environmental epidemiology, risk assessment and management, as well as regulatory actions. The current state of knowledge on exposure to carbon-based fibrous nanomaterials among workers, consumers and general population was studied in frame of the International Agency for Research on Cancer (IARC) Monographs-Volume 111 "Some Nanomaterials and Some Fibres". Completeness and reliability of available exposure data for use in epidemiology and risk assessment were assessed.

Quantification of short and long asbestos fibers to assess asbestos exposure: a review of fiber size toxicity.

The fibrogenicity and carcinogenicity of asbestos fibers are dependent on several fiber parameters including fiber dimensions. Based on the WHO (World Health Organization) definition, the current regulations focalise on long asbestos fibers (LAF) (Length: L ≥ 5 μm, Diameter: D < 3 μm and L/D ratio > 3). However air samples contain short asbestos fibers (SAF) (L < 5 μm).

Short, fine and WHO asbestos fibers in the lungs of quebec workers with an asbestos-related disease.

Background: The possible role of short asbestos fibers in the development of asbestos-related diseases and availability of lung fiber burden data prompted this study on the relationships between fiber characteristics and asbestos-related diseases among compensated workers.

Methods: Data collected between 1988 and 2007 for compensation purposes were used; lung asbestos fibers content of 123 Quebec workers are described according to socio-demographic characteristics, job histories and diseases (asbestosis, mesothelioma, lung cancer).

Results: Most workers (85%) presented chrysotile fibers in their lungs, and respectively 76%, 64%, and 43% had tremolite, amosite, and crocidolite.

Assessment of the contribution of electron microscopy to nanoparticle characterization sampled with two cascade impactors.

This study assessed the contribution of electron microscopy to the characterization of nanoparticles and compared the degree of variability in sizes observed within each stage when sampled by two cascade impactors: an Electrical Low Pressure Impactor (ELPI) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). A TiO(2) nanoparticle (5 nm) suspension was aerosolized in an inhalation chamber. Nanoparticles sampled by the impactors were collected on aluminum substrates or TEM carbon-coated copper grids using templates, specifically designed in our laboratories, for scanning and transmission electron microscopy (SEM, TEM) analysis, respectively.

Generating nano-aerosols from TiO₂ (5 nm) nanoparticles showing different agglomeration states. Application to toxicological studies.

Agglomeration of nanoparticles (NP) is a key factor in the generation of aerosols from nano-powders and may represent an important parameter to consider in toxicological studies. For this reason, the characterization of NP aerosols (e.g.

Occupational exposure to silica in construction workers: a literature-based exposure database.

We created an exposure database of respirable crystalline silica levels in the construction industry from the literature. We extracted silica and dust exposure levels in publications reporting silica exposure levels or quantitative evaluations of control effectiveness published in or after 1990. The database contains 6118 records (2858 of respirable crystalline silica) extracted from 115 sources, summarizing 11,845 measurements.

Silica exposure during construction activities: statistical modeling of task-based measurements from the literature.

Many construction activities can put workers at risk of breathing silica containing dusts, and there is an important body of literature documenting exposure levels using a task-based strategy. In this study, statistical modeling was used to analyze a data set containing 1466 task-based, personal respirable crystalline silica (RCS) measurements gathered from 46 sources to estimate exposure levels during construction tasks and the effects of determinants of exposure. Monte-Carlo simulation was used to recreate individual exposures from summary parameters, and the statistical modeling involved multimodel inference with Tobit models containing combinations of the following exposure variables: sampling year, sampling duration, construction sector, project type, workspace, ventilation, and controls.

Statistical modeling of crystalline silica exposure by trade in the construction industry using a database compiled from the literature.

A quantitative determinants-of-exposure analysis of respirable crystalline silica (RCS) levels in the construction industry was performed using a database compiled from an extensive literature review. Statistical models were developed to predict work-shift exposure levels by trade. Monte Carlo simulation was used to recreate exposures derived from summarized measurements which were combined with single measurements for analysis.

Physical and chemical characterization of beryllium particles from several workplaces in Québec, Canada--part B: time-of-flight secondary-ion mass spectroscopy.

The problems associated with detecting and characterizing beryllium (Be) particles in industrial samples from Québec were addressed in the companion article (Rouleau et al., 2005). The present study is a continuation of the work aimed at redefining the current occupational exposure level for beryllium.

Physical and chemical characterization of beryllium particles from several workplaces in Québec, Canada--part A: determining methods for the analysis of low levels of beryllium.

Chemical and physical characterizations of beryllium (Be) particles found in settled dust samples from four industries based in Québec were attempted using a variety of analytical methods. Bulk particle chemistry was determined using inductively coupled plasma-mass spectrometry (ICP-MS), graphite furnace atomic absorption spectrometry (GFAAS), and instrumental neutron activation analysis (INAA). Time-of-flight secondary-ion mass spectrometry (TOF-SIMS), transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction (XRD), electron energy loss spectrometry (EELS), and Auger microscopy were used to characterize physicochemical properties of particles.

Assessment of exposure to quartz, cristobalite and silicon carbide fibres (whiskers) in a silicon carbide plant.

The main objective of the present paper is to report on the concentration of silicon carbide (SiC) fibres, crystalline silica and respirable dust in a Canadian SiC production plant and to compare the results with earlier investigations. The second objective is to tentatively explain the differences in concentration of the fibrogenic substances between different countries. The assessment of SiC fibres, dusts, respirable quartz and cristobalite was performed according to standard procedures.