Maximilien Debia

Case Study: Ultrafine Particles Exposure in Apprentice Welders

Ultrafine particles (UFPs) are generally defined as those particles with a diameter less than 100 nanometer (nm) that are not intentionally generated (i.e., engineered nanoparticles). Sources of UFPs exist in a number of industrial settings, including smelters,(1–3) arc spraying,(4) high-speed grinding,(5) foundries,(6) micromachining processes,(7) and various other job activities.(8) Several authors have also shown that welding fumes are mostly composed of fine and ultrafine particles.(9–13) Hewett(14) showed, during welding fume emission, particle size distributions having mass geometric means ranging from 0.46 to 0.59 μm. Elihn et al.(8) showed that 20% to 60% of particles emitted during the welding process were less than 100 nm. Isaxon et al.(15) proposed that the signature size distributions of metal active gas (MAG)-welding appears as a single mode with mass median aerodynamic diameter of 200–300 nm, while stick welding generated larger particles. Likewise, Stephenson et al.(16) noted significant UFP production during shielded metal arc welding (SMAW) of carbon steel but did not quantitatively examine potential determinants of exposure.(16) Brand et al.(17) monitored the particle size distributions of various welding and joining techniques in standardized laboratory conditions and noted UFP composition differences between processes with high mass emission rates (SMAW, MAG welding, metal inert gas welding, metal inert gas soldering, and laser welding) and welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding). This issue of occupational UFP exposures is of increasing importance as evidence suggests that UFPs are potent triggers of oxidative stress and may contribute to adverse respiratory and cardiovascular outcomes.(18–24) Moreover, specific exposure to welding fumes is known to cause respiratory and cardiovascular health problems. Antonini et al.(25) reported respiratory effects among welders including bronchitis, airway irritation, lung function changes, and a possible increase in the incidence of lung cancer. Welding is a process in which gaseous and aerosol byproducts composed of a complex array of metals, metal oxides, and other chemical species are produced. Specific health outcomes are also associated to each fraction, and the particulate emissions intrinsic of the welding fume have been classified as a possible human carcinogen by the International Agency for Research on Cancer.(26) Furthermore, exposures among apprentice welders are particularly relevant as epidemiological evidence suggests that these workers may experience decreased lung function as a result of occupational exposures.(27) Burgess(28) described that health hazards associated with any welding operations are a function of the welding operation itself, the filler metal, the base metal, the base metal protective coating, the shielding gas or rod coating, the reactions occurring during welding, and welding conditions. In addition, exposure to welding

Exposure Assessment in a Single-Walled Carbon Nanotube Primary Manufacturer

Objectives This study was aimed at documenting and characterizing occupational exposure to single-walled carbon nanotubes (SWCNTs) generated in a primary manufacturing plant. It also compared various strategies of exposure monitoring. Methods A 6-day measurement protocol was scheduled (D1-D6) including both (i) quasi-personal monitoring with an array of direct reading instruments (DRIs) and (ii) offline electron microscopy analyses of surface and breathing zone filter-based samples. The first step (D1 and D2) consisted of contamination screenings resulting from the various SWCNT production tasks using a multimetric approach. Surface sampling was also carried out to assess workplace cross-contamination. The second step (D3-D6) focused on the exposure monitoring during recovery/cleaning task, by comparing three personal elemental carbon (EC) measurements [respirable EC using a cyclone following the NIOSH 5040 method (REC-CYC), respirable and thoracic EC using parallel particle impactors [REC-PPI and TEC-PPI, respectively)] and gravimetric mass concentration measurements. Results DustTrak DRX and electrical low-pressure impactor measurements indicated that particles were released during weighing, transferring, and recovery/cleaning tasks of the manufacturing process. Electron microscopy revealed the presence of agglomerated SWCNTs only during the recovery/cleaning task. REC-CYC concentrations remained under the limits of quantification; REC-PPI showed levels up to 58 µg m-3; and TEC-PPI ranged from 40 to 70 µg m-3. Ratios calculated between gravimetric measurements and estimated DustTrak mass concentrations ranged from 2.8 to 4.9. Cross-contamination appeared to be limited since SWCNTs was only found on surface samples collected close to the reactor in the production room. Conclusions This case study showed that the DustTrak DRX should be the preferred device among DRIs to identify potential exposure to SWCNTs. However, there is a risk of false positive since it is a non-specific instrument; therefore, the actual release of SWCNTs must be confirmed with scanning electron microscopy/transmission electron microscopy analyses. Besides, using EC measurements as a proxy for SWCNT exposure assessments, as suggested by the NIOSH, is still challenging since interferences can occur with other EC sources such as carbon black, which is also present in the workplace.

Overview of Workplace Exposure to Nanomaterials

Exposure assessment is a critical step in the toolbox of the occupation health and safety risk management strategy. It is even more relevant in the case of new contaminants as engineered nanomaterials since it allows identifying sectors of activity and tasks where efforts are needed in order to minimize risks for health and safety. This chapter starts with a review of possible situations of workplace exposures to nanomaterials. It follows with a description of methods available for assessing occupational exposures to nanomaterials. Results of studies and measurements of workplace exposure in production, downstream manipulation, use as input material or tool for further processing, and at end of life are then presented. They showed in some instances the release of free nanoparticles, which may induce potential risks for workers. In general, good work practices were found to be efficient for reducing risk of exposure to nanomaterials. This chapter also describes strategies and tools proposed to reduce occupational exposure to engineered nanomaterials, and discusses the challenges faced by professionals and researchers involved in. It ends with a list of international initiatives and future trends in that domain.

ÉquiNanos: innovative team for nanoparticle risk management

UNLABELLED Interactions between nanoparticles (NP), humans and the environment are not fully understood yet. Moreover, frameworks aiming at protecting human health have not been adapted to NP but are nonetheless applied to NP-related activities. Consequently, business organizations currently have to deal with NP-related risks despite the lack of a proven effective method of risk-management. To respond to these concerns and fulfill the needs of populations and industries, ÉquiNanos was created as a largely interdisciplinary provincial research team in Canada. ÉquiNanos consists of eight platforms with different areas of action, from adaptive decision-aid tool to public and legal governance, while including biological monitoring. ÉquiNanos resources aim at responding to the concerns of the Quebec nanotechnology industry and public health authorities. Our mandate is to understand the impact of NP on human health in order to protect the population against all potential risks emerging from these high-priority and rapidly expanding innovative technologies. FROM THE CLINICAL EDITOR In this paper by Canadian authors an important framework is discussed with the goal of acquiring more detailed information and establishing an infrastructure to evaluate the interaction between nanoparticles and living organisms, with the ultimate goal of safety and risk management of the rapidly growing fields of nanotechnology-based biological applications.

Comparison between personal sampling methodologies for evaluating diesel particulate matter exposures in mines: submicron total carbon corrected for the adsorption of vapor-phase organic carbon versus respirable total carbon

Abstract In the mining industry, personal measurements of elemental and total carbon are frequently used as surrogates of diesel particulate matter (DPM) exposure, and the respirable or submicron fractions are usually measured. However, vapor-phase organic carbon (OC) can be adsorbed in the filters, interfering with total carbon results. This study presents a comparative evaluation between the submicron fraction of DPM concentrations corrected for the adsorption of the vapor-phase OC (dynamic blank), and the respirable fraction of DPM corrected for a field blank. Respirable and submicron fractions of total carbon (TCR and TC1) and elemental carbon (ECR and EC1) concentrations were sampled in parallel, in the workers’ breathing zone, in an underground gold mine. A total of 20 full-shift personal samples were taken for each size fraction. Field blanks were collected each day for both the submicron and respirable fractions, while dynamic blank correction was also applied for the submicron fraction. TCR presented a larger and statistically different geometric mean concentration compared to TC1 (98 µg/m3 vs. 72 µg/m3; p = 0.01), while the concentrations of ECR and EC1 were not statistically different (58 µg/m3 vs. 54 µg/m3; p = 0.74). Average TCR/ECR ratio was 1.7, while the TC1/EC1 ratio was 1.3. In addition, 93% of EC had an aerodynamic size lower than 1 µm, while the proportion of TC particles in the submicron fraction was lower (73%). Finally, a similar quantity of OC was found when analyzing the dynamic and field blanks of the filters with the submicron fraction selective size (24 µg and 22 µg, respectively). In conclusion, the correction for the vapor phase OC by the dynamic blank was not a significant correction in our study design compared to the field blank samples. This study suggests that the differences in TC may be explained by the different aerodynamic fractions of DPM collected. In addition, elemental carbon measurements did not seem to be extensively affected by the aerodynamic size of the particles collected.

Diesel engine exhaust exposure in underground mines: Comparison between different surrogates of particulate exposure

ABSTRACT Exposure to diesel particulate matter (DPM) is frequently assessed by measuring indicators of carbon speciation, but these measurements may be affected by organic carbon (OC) interference. Furthermore, there are still questions regarding the reliability of direct-reading instruments (DRI) for measuring DPM, since these instruments are not specific and may be interfered by other aerosol sources. This study aimed to assess DPM exposure in 2 underground mines by filter-based methods and DRI and to assess the relationship between the measures of elemental carbon (EC) and the DRI to verify the association of these instruments to DPM. Filter-based methods of respirable combustible dust (RCD), EC, and total carbon (TC) were used to measure levels of personal and ambient DPM. For ambient measurements, DRI were used to monitor particle number concentration (PNC; PTrak), particle mass concentration (DustTrak DRX and DustTrak 8520), and the submicron fraction of EC (EC1;Airtec). The association between ambient EC and the DRI was assessed by Spearman correlation. Geometric mean concentrations of RCD, respirable TC (TCR) and respirable elemental EC (ECR) were 170 µg/m3, 148 µg/m3, and 83 µg/m3 for personal samples, and 197 µg/m3, 151 µg/m3, and 100 µg/m3 for ambient samples. Personal measurements had higher TCR:ECR ratios compared to ambient samples (1.8 vs. 1.50) and weaker association between ECR and TCR. Among the DRI, the measures of EC1 by the Airtec (ρ = 0.86; P < 0.001) and the respirable particles by the DustTrak 8520 (ρ = 0.74; P < 0.001) showed the strongest association with EC, while PNC showed a weak and non-significant association with EC. In conclusion, this study provided important information about the concentrations of DPM in underground mines by measuring several indicators using filter-based methods and DRI. Among the DRI, the Airtec proved to be a good tool for estimating EC concentrations and, although the DustTrak showed good association with EC, interferences from other aerosol sources should be considered when using this instrument to assess DPM.

Effect of the Primary Nanoscale Size, Agglomeration State and Concentrations on the Toxicokinetics of Titanium Dioxide (TiO2) Nanoparticles after Inhalation in Rats

The impact of different inhalation exposure conditions to aerosols of titanium dioxide (TiO2) nanoparticles (NPs) on the disposition kinetics of titanium (Ti) element in rats was studied. Rats were exposed nose-only by inhalation to the anatase form of TiO2 NPs during 6 h under different conditions (1 and 7 mg/m3 of NPs of 20 nm primary diameter, less agglomerated; 15 mg/m3 of NPs of 7, 20 and 50 nm, less agglomerated; 15 mg/m3 of NPs of 20 nm, more agglomerated). The time courses of Ti in lungs, blood, tissues and excreta were established over 72-h following the onset of inhalation. Highest tissue levels of Ti were found in lungs and were dependent on: 1) TiO2 exposure concentrations (monitored mean of 1, 7, 15 mg/m3 and 31,000, 446,000, 786,000 particles/cm3, and similar agglomeration state of 20 nm NPs with average of 76-80 nm); 2) agglomeration state of NPs (monitored mean size of agglomerates of 20 nm NPs of 134 versus 76 nm for an monitored mean concentration of 15 mg/m3). When generating similar size distribution of agglomerates of 20 nm NPs (mean of 74 to 76 nm) for a monitored mean exposure concentration of 15 mg/m3, there was no impact of the studied primary size of NPs (7, 20 or 50 nm) on pulmonary Ti levels, as expected. For all tested exposure conditions, translocation to blood and lymph nodes as well as distribution to extrapulmonary organs were limited with only slight increases compared to pre-exposure and control levels. However, the size of agglomerates (134 versus 76 nm) appeared to have a slight impact on the transfer of Ti element to blood and lymph nodes. Overall, the size of the agglomerates appeared as the main factor determining site-of-entry retention and – although limited – transfer of NPs into the systemic circulation.

Assessment of Workers’ Exposure to Grain Dust and Bioaerosols During the Loading of Vessels’ Hold: An Example at a Port in the Province of Québec

Longshoremen are exposed to large amounts of grain dust while loading of grain into the holds of vessels. Grain dust inhalation has been linked to respiratory diseases such as chronic bronchitis, hypersensitivity, pneumonitis, and toxic pneumonitis. Our objective was to characterize the exposure of longshoremen to inhalable and total dust, endotoxins, and cultivable bacteria and fungi during the loading of grain in a vessels hold at the Port of Montreal in order to assess the potential health risks. Sampling campaigns were conducted during the loading of two different types of grain (wheat and corn). Environmental samples of microorganisms (bacteria, fungus, and actinomycetes) were taken near the top opening of the ships holds while personal breathing zone measurements of dust and endotoxins were sampled during the workers 5-hour shifts. Our study show that all measurements are above the recommendations with concentration going up to 390 mg m-3 of total dust, 89 mg m-3 of inhalable fraction, 550 000 EU m-3 of endotoxins, 20 000 CFU m-3 of bacteria, 61 000 CFU m-3 of fungus and 2500 CFU m-3 of actinomycetes. In conclusion, longshoremen are exposed to very high levels of dust and of microorganisms and their components during grain loading work. Protective equipment needs to be enforced for all workers during such tasks in order to reduce their exposure.

Risk Management and Good Practices Guidelines

Abstract Numerous studies indicate that workers exposed to some engineered nanomaterials (ENMs) could be at risk of developing adverse health effects. In the absence of regulated occupational exposure limits and because toxicological data as well as exposure levels are still limited, the risk is normally impossible to fully quantify in most workplaces. Alternative qualitative or semiquantitative approaches such as control banding are widely used to take into consideration these uncertainties to safely manage the exposures in several situations. Overall, risk management programs based on the precautionary approach should be carried out to minimize exposures to ENMs. These programs, elaborated at the design stage, should include intrinsic safety, engineering controls, administrative procedures, and personal protective equipment. Train and raise the safety awareness of workers, evaluate the efficiency of the preventive measures, and establish safe work practices and good emergency plans are essential constituents of the prevention program.

Do existing empirical models for welding fumes estimate exposure to ultrafine particles among canadian welding apprentices

Background: An exposure study in Quebec showed that apprentices in welding profession have a high level of exposure to ultrafine particles (UFP) during the whole training period.This is of increasing importance as evidence suggests that UFP may contribute to adverse respiratory and cardiovascular outcomes. We evaluated how well existing empirical models for welding fumes estimate exposure to UFP among welding apprentices. Methods: We used an existing exposure database of 136 UFP measurements from two welding vocational schools in Quebec. We used three exposure models for inhalable dusts and fumes, respirable dusts and fumes, and total particulate matter to estimate UFP exposure among apprentice welders from Quebec. Pearson correlation coefficients were calculated between the estimated exposure to welding fumes based on the three models and measured UFP concentrations. Results: Low correlation coefficients were found between the measured UFP concentrations and the estimated welding fumes concentrations from the three exposure models that ranged from 0.11 to 0.22. Correlations coefficients between the estimates of the three models were markedly higher and ranged from 0.41 to 0.74. Conclusions: Current empirical models for exposure to welding fumes are insufficient for predicting exposure to UFP among welding apprentices. More UFP measurements are needed to derive UFP-specific empirical models. These models will be crucial for controlling exposure and to assess association of exposure to UFP and respiratory health effects.