Yves Cloutier

Prepolymers of hexamethylene diisocyanate as a cause of occupational asthma

BACKGROUND Occupational asthma (OA) caused by products that contain hexamethylene diisocyanate (HDI) has been ascribed to the highly volatile monomer of HDI. Most two-component paints are now made up primarily of nonvolatile prepolymers of HDI (30% to 60%) with only trace amounts (< 0.1%) of the monomer. The respective role of the two chemical forms of HDI in causing OA has never been investigated. METHODS Twenty workers who were consecutively referred for possible OA that resulted from exposure to spray paints underwent inhalation challenges on separate days with pure HDI monomer and the commercial formulation of HDI prepolymers to which they had been exposed at work. RESULTS Specific inhalation challenges elicited a positive asthmatic reaction in 10 of the 20 subjects. Among these subjects, four had positive bronchial reactions (two early, one late, and one dual) to both the monomer and the prepolymers. Four other subjects had asthmatic reactions (two early, one late, and one dual) after exposure to the prepolymers but not after exposure to the monomer. The discordance in bronchial response elicited by the monomer and the prepolymers could not be due to differences in the level of baseline nonspecific bronchial reactivity or in HDI concentrations during the tests. One subject showed an atypical progressive reaction after exposure to the monomer but not after exposure to the prepolymer. In this case, the discordant response could be explained by differences in HDI concentration. CONCLUSION These observations show that, although they are nonvolatile, the prepolymers of HDI can induce OA and that asthmatic reactions as a result of exposure to prepolymers but not the monomer is not a rare occurrence.

Effects of inhaled nano-TiO2 aerosols showing two distinct agglomeration states on rat lungs

Nano-aerosols composed of large agglomerates (LA) (>100nm) are more likely to promote pulmonary clearance via macrophages phagocytosis. Small agglomerates (SA) (<100nm) seem to escape this first defense mechanism and are more likely to interact directly with biological material. These different mechanisms can influence pulmonary toxicity. This hypothesis was evaluated by comparing the relative pulmonary toxicity induced by aerosolized nano-TiO(2) showing two different agglomeration states: SA (<100nm) and LA (>100nm) at mass concentrations of 2 or 7mg/m(3). Groups of Fisher 344 male rats were nose-only exposed for 6h. The median number aerodynamic diameters were 30 and 185nm at 2mg/m(3), and 31 and 194nm at 7mg/m(3). We found in rats bronchoalveolar lavage fluids (BALF) a significant 2.1-fold increase in the number of neutrophils (p<0.05) in the group exposed to the 7mg/m(3) LA nano-aerosol suggesting a mild inflammatory response. Rats exposed to the 7mg/m(3) SA nano-aerosol showed a 1.8-fold increase in LDH activity and 8-isoprostane concentration in BALF, providing evidence for cytotoxic and oxidative stress effects. Our results indicate that biological responses to nanoparticles (NP) might depend on the dimension and concentration of NP agglomerates.

Rat pulmonary responses to inhaled nano-TiO2: effect of primary particle size and agglomeration state

BackgroundThe exact role of primary nanoparticle (NP) size and their degree of agglomeration in aerosols on the determination of pulmonary effects is still poorly understood. Smaller NP are thought to have greater biological reactivity, but their level of agglomeration in an aerosol may also have an impact on pulmonary response. The aim of this study was to investigate the role of primary NP size and the agglomeration state in aerosols, using well-characterized TiO2 NP, on their relative pulmonary toxicity, through inflammatory, cytotoxic and oxidative stress effects in Fisher 344 male rats.MethodsThree different sizes of TiO2 NP, i.e., 5, 10–30 or 50 nm, were inhaled as small (SA) (< 100 nm) or large agglomerates (LA) (> 100 nm) at 20 mg/m3 for 6 hours.ResultsCompared to the controls, bronchoalveolar lavage fluids (BALF) showed that LA aerosols induced an acute inflammatory response, characterized by a significant increase in the number of neutrophils, while SA aerosols produced significant oxidative stress damages and cytotoxicity. Data also demonstrate that for an agglomeration state smaller than 100 nm, the 5 nm particles caused a significant increase in cytotoxic effects compared to controls (assessed by an increase in LDH activity), while oxidative damage measured by 8-isoprostane concentration was less when compared to 10–30 and 50 nm particles. In both SA and LA aerosols, the 10–30 nm TiO2 NP size induced the most pronounced pro-inflammatory effects compared to controls.ConclusionsOverall, this study showed that initial NP size and agglomeration state are key determinants of nano-TiO2 lung inflammatory reaction, cytotoxic and oxidative stress induced effects.

Evaluation of bacterial contamination and control methods in soluble metalworking fluids.

In the United States, 1.2 million workers are exposed to metalworking fluids. During operations, aerosols are produced and airborne contaminants can be inhaled. Although biocides are used to control the bacterial content of metalworking fluids, they can create health-related problems, and their efficiency remains to be proved. The objectives of this project were (1) to verify whether rigorous cleaning according to a standard protocol could reduce microbial contamination and (2) whether the use of biocides with different spectra could reduce the bacterial population. Four similar machines producing similar components were evaluated; a specific treatment was applied to each machine. The machine used as a control (1) was thoroughly cleaned prior to sampling, (2) did not undergo any major cleaning afterward, and (3) was operated without the use of any biocide. A major cleaning is a protocol described and recommended by the fluid manufacturer and was performed on the three other machines, two of which were subsequently treated with biocides weekly. Fluid samples from the four lathes were collected weekly during a 6-month period, and total bacterial and cultivable Gram-negative bacteria were analyzed for each sample. Major cleaning of the machines (120–4) did not significantly reduce the concentration of bacteria in the cutting fluids when compared with the control machine (120–3), which had not undergone major cleaning. The concentrations of total bacteria were in the 10 6 CFU/mL range for these two lathes; however, a reduction in the total number of fluid changes was observed for this machine. Bacterial flora in the cutting fluids was significantly controlled with the use of biocides. Bacteria concentrations were in the 10 3 –10 5 CFU/mL range for the lathes with the use of biocides. Since thorough cleaning is insufficient and biocides are recognized as being responsible for some worker health problems, other avenues for controlling bacterial flora in cutting fluids should be evaluated to reduce worker exposure to their bacterial contaminants.

Impact of emerging pollutants on pulmonary inflammation in asthmatic rats: ethanol vapors and agglomerated TiO2 nanoparticles

Context: Titanium dioxide nanoparticles (nano-TiO2) and ethanol vapors are air contaminants with increasing importance. The presence of a pathological pulmonary condition, such as asthma, may increase lung susceptibility to such contaminants. Objective: This study aimed to investigate if exposure to inhaled ethanol vapors or nano-TiO2 can modulate the rat pulmonary inflammatory response resulting from an allergic asthmatic reaction. Materials and methods: Brown Norway rats were sensitized (sc) and challenged (15 min inhalation, 14 days later) with chicken egg ovalbumin (OVA). Leukocytes were counted in bronchoalveolar lavages (BAL) performed at 6, 24, 36, 48 and 72 h following the challenge and either after ethanol exposures (3000 ppm, 6 h/day, daily) or at 48 h (peak inflammation) for nano-TiO2 exposures (9.35 mg/m3 aerosol for 6 and 42 h after the OVA challenge). For the nano-TiO2 exposures, plasma and BAL cytokines were measured and lung histological analyzes were performed. Results: Exposure to ethanol did not significantly affect BAL leukocytes after OVA challenge. Exposure to nano-TiO2 significantly decreased BAL leukocytes compared to OVA-challenged controls. Plasma and BAL IL-4, IL-6, and INF-γ levels were also decreased in the nano-TiO2 group. Discussion: While ethanol vapors do not modify the pulmonary inflammation in rats during an asthmatic response, a surprising protective effect for agglomerated nano-TiO2 was observed. A putative mechanistic basis involving a decrease in the Th2 response caused by OVA is proposed. Conclusion: Allergic pulmonary inflammation is not up-regulated by inhalation of the pollutants ethanol and nano-TiO2. On the contrary, nano-TiO2 decreases lung inflammation in asthmatic rats.

Quantitative determination of hexamethylene diisocyanate (HDI), 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) monomers at ppt levels in air by alkaline adduct coordination ionspray tandem mass spectrometry

Occupational exposures to isocyanates can lead to occupational asthma. Once sensitized, some workers could react to isocyanate monomers at concentrations below 1% of the Permissible Exposure Limit of 5 ppb in air. Currently available methods are not sufficiently sensitive to adequately evaluate isocyanates present at these levels in workplace air. This article describes a novel method for isocyanate determination allowing the ultratrace quantification in workplace air of hexamethylene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate monomers. Sampling is performed during a complete workshift at a flow rate of 1 L min(-1) with a cassette containing a 1-(2-methoxyphenyl)piperazine-impregnated 25 mm filter. Analysis is performed using liquid chromatography hyphenated with coordination ionspray tandem mass spectrometry. The analytical methods linearity was measured for a concentration range varying from the limit of detection of 0.04-0.13 ng mL(-1), depending on the monomer, up to approximately 32 ng mL(-1) for every isocyanate monomer, all with correlation coefficients (R(2)) greater than 0.999. The analytical methods lower limit of quantification combined with an adapted sampling strategy allow the quantification of isocyanate monomers down to 0.04 ppt for an 8 h work shift when a lithium adduct is used, which is more than 300 times lower than the most sensitive method currently available. This novel method can be used to confirm the very low level of isocyanate monomers for the safe reassignment of sensitized workers and it is also useful for charting the isocyanate dispersion tail in workplace environments.

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., concentration, size, and structure of agglomerates) is a critical step in the determination of the relationship between exposure and effects. The aim of this study was to generate and characterize aerosols composed of TiO2 (5 nm) NP showing different agglomeration states. Two concentrations were tested: 2 and 7 mg/m3. Stable mass concentrations over 6 hr were successfully generated by a wet method using Collison and Delavan nebulizers that resulted in aerosols composed of smaller agglomerates (<100 nm), while aerosols composed of larger agglomerates (>100 nm) were obtained by dry generation techniques using either a Palas dust feeder or a Fluidized Bed. Particle size distributions in the aerosols were determined by an electrical low pressure impactor. Median number aerodynamic diameters corresponding to the aerosol with smaller and larger agglomerates were 30 and 185 nm, respectively, for the 2 mg/m3 concentration, and 31 and 194 nm for the 7 mg/m3 experiment. Image analysis by transmission electron microscopy showed the presence of compact or agglomerates with void spaces in the different nano-aerosols. These characterized nano-aerosols will be used in further experiments to study the influence of agglomerate size on NP toxicity.

Impact of two particle measurement techniques on the determination of N95 class respirator filtration performance against ultrafine particles.

The purpose of this experimental study was to compare two different particle measurement devices; an Electrical Low Pressure Impactor (ELPI) and a Scanning Mobility Particle Sizer (SMPS), to measure the number concentration and the size distribution of NaCl salt aerosols to determine the collection efficiency of filtering respirators against poly disperse aerosols. Tests were performed on NIOSH approved N95 filtering face-piece respirators (FFR), sealed on a manikin head. Ultrafine particles found in the aerosols were also collected and observed by transmission electron microscopy (TEM). According to the results, there is a systematic difference for the particle size distribution measured by the SMPS and the ELPI. It is largely attributed to the difference in the measurement techniques. However, in spite of these discrepancies, reasonably similar trends were found for the number concentration with both measuring instruments. The particle penetration, calculated based on mobility and aerodynamic diameters, never exceeded 5% for any size range measured at constant flow rate of 85 L/min. Also, the most penetrating particle size (MPPS), with the lowest filtration efficiency, would occur at a similar ultrafine size range <100 nm. With the ELPI, the MPPS was at 70 nm aerodynamic diameter, whereas it occurred at 40 nm mobility diameter with the SMPS.

CIP10 Optimization for 4,4-Methylene Diphenyl Diisocyanate Aerosol Sampling and Field Comparison With Impinger Method

4,4-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known as being a challenge because the spray foam application actually involves a fast-curing process. Available techniques are either not user-friendly or are inaccurate or not validated for this application. To address these issues, a new approach using a CIP10M was developed to appropriately collect MDI aerosol in spray foam insulation while being suitable for personal sampling. The CIP10M is a commercially available personal aerosol sampler that has been validated for the collection of microbial spores into a liquid medium. Tributylphosphate with 1-(2-methoxyphenyl)piperazine (MOPIP) was introduced into the CIP10M to collect and stabilize the MDI aerosols. The limit of detection and limit of quantification of the method were 0.007 and 0.024 μg ml(-1), respectively. The dynamic range was from 0.024 to 0.787 μg ml(-1) (with R (2) ≥ 0.990), which corresponds to concentrations in the air from 0.04 to 1.3 µg m(-3), assuming 60 min of sampling at 10 l min(-1). The intraday and interday analytical precisions were <2% for all of the concentration levels tested, and the accuracy was within an appropriate range of 98 ± 1%. No matrix effect was observed, and a total recovery of 99% was obtained. Parallel sampling was performed in a real MDI foam spraying environment with a CIP10M and impingers containing toluene/MOPIP (reference method). The results obtained show that the CIP10M provides levels of MDI monomer in the same range as the impingers, and higher levels of MDI oligomers. The negative bias observed for MDI monomer was between 2 and 26%, whereas the positive bias observed for MDI oligomers was between 76 and 113%, with both biases calculated with a confidence level of 95%. The CIP10M seems to be a promising approach for MDI aerosol exposure evaluation in spray foam applications.

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 TiO2 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. Nanoparticles were characterized using both SEM and TEM. Three different types of diameters (inner, outer, and circular) were measured by image analysis based on count and volume, for each impactor stage. Electron microscopy, especially TEM, is well suited for the characterization of nanoparticles. The MOUDI, probably because of the rotation of its collection stages, which can minimize the resuspension of particles, gave more stable results and smaller geometric standard deviations per stage. Our data suggest that the best approach to estimate particle size by electron microscopy would rely on geometric means of measured circular diameters. Overall, the most reliable data were provided by the MOUDI and the TEM sampling technique on carbon-coated copper grids for this specific experiment. This study indicates interesting findings related to the assessment of impactors combined with electron microscopy for nanoparticle characterization. For future research, since cascade impactors are extensively used to characterize nano-aerosol exposure scenarios, high-performance field emission scanning electron microscopy (FESEM) should also be considered.