Impact of low dose chlorine inhalation in healthy humans: a pilot study

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Mass or total surface area with aerosol size distribution as exposure metrics for inflammatory, cytotoxic and oxidative lung responses in rats exposed to titanium dioxide nanoparticles.

There is currently no consensus on the best exposure metric(s) for expressing nanoparticle (NP) dose. Although surface area has been extensively studied for inflammatory responses, it has not been as thoroughly validated for cytotoxicity or oxidative stress effects. Since inhaled NPs deposit and interact with lung cells based on agglomerate size, we hypothesize that mass concentration combined with aerosol size distribution is suitable for NP risk assessment. The objective of this study was to evaluate different exposure metrics for inhaled 5 nm titanium dioxide aerosols composed of small (SA < 100 nm) or large (LA > 100 nm) agglomerates at 2, 7, and 20 mg/m3 on rat lung inflammatory, cytotoxicity, and oxidative stress responses. We found a significant positive correlation ( r = 0.98, p < 0.01) with the inflammatory reaction, measured by the number of neutrophils and the mass concentration when considering all six (SA + LA) aerosols. This correlation was similar ( r = 0.87) for total surface area. Regarding cytotoxicity and oxidative stress responses, measured by lactate dehydrogenase and 8-isoprostane, respectively, and mass or total surface area as an exposure metric, we observed significant positive correlations only with SA aerosols for both the mass concentration and size distribution ( r > 0.91, p < 0.01), as well as for the total surface area ( r > 0.97, p < 0.01). These data show that mass or total surface area concentrations alone are insufficient to adequately predict oxidant and cytotoxic pulmonary effects. Overall, our study indicates that considering NP size distribution along with mass or total surface area concentrations contributes to a more mechanistic discrimination of pulmonary responses to NP exposure.

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 rat's 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.

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

CONTEXT: Titanium dioxide nanoparticles (nano-TiO(2)) 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-TiO(2) 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-TiO(2) exposures (9.35 mg/m(3) aerosol for 6 and 42 h after the OVA challenge). For the nano-TiO(2) 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-TiO(2) 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-TiO(2) group. DISCUSSION: While ethanol vapors do not modify the pulmonary inflammation in rats during an asthmatic response, a surprising protective effect for agglomerated nano-TiO(2) 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-TiO(2). On the contrary, nano-TiO(2) decreases lung inflammation in asthmatic rats.

Beryllium aerosol characteristics in the magnesium and aluminum transformation industry in Quebec: a comparison of four different sampling methodologies.

To examine the influence of the sampling method on beryllium (Be) exposure assessment, a study was conducted in foundries and smelters to contrast the performance of five different dust sampling devices. Six sampling surveys were conducted in four different settings, and both personal and fixed station samples were collected using the following sampling heads: IOM samplers (inhalable dust), 35-mm plastic cassettes (total dust), aluminum SKC cyclones (respirable dust), 8-stage Sierra cascade impactors, and 12-stage MOUDI impactors. In total, beryllium concentrations were determined for 66/68 inhalable dust samples, 62/62 total dust samples, 56/57 respirable dust samples, 54/64 8-stage Sierra samples, and 19/25 12-stage MOUDI samples. In the magnesium foundry and aluminum smelters, the concentrations obtained during specific tasks could exceed the actual permissible exposure limit of the province of Quebec (0.15 microg/m(3)) or of the ACGIH threshold limit value (TLV) (0.05 microg/m(3)). The median of median dust concentration ratios computed from the sampling heads at the fixed station decreased as follows: IOM (1.00) > Sierra (0.76) > 37-mm cassette (0.61) > MOUDI (0.48) > respirable (0.12). The same trends were observed with the ratios of the median of median Be concentrations at the fixed station but with a larger scattering within sampling heads as follows: IOM (1.00) > Sierra (0.69) > 37-mm cassette (0.64) > MOUDI (0.54) > respirable (0.19). The median of median ratios of dust (IOM (1.00) > Sierra (0.56) > 37-mm cassette (0.35) > respirable (0.06)) and Be (IOM (1.00) > Sierra (0.66) > 37-mm cassette (0.48) > respirable (0.11)) in dust were lower, and there was less scattering for the 37-mm cassette and SKC cyclone used during breathing zone sampling than for the same sampling heads at the fixed station. Inhalable aerosol measurements should remain the tool for estimating the risk of exposure to beryllium in these settings until a clear dose response is established for these sampling heads.

Exaggerated bronchoconstriction due to inhalation challenges with occupational agents.

Inhalation challenges with occupational agents are used to confirm the aetiology of occupational asthma. It has been proposed that using closed-circuit equipment rather than the realistic challenge method would improve the methodology of these tests. Changes in forced expiratory volume in one second (FEV1) were examined in 496 subjects with "positive specific inhalation challenges", i.e. changes in FEVI of > or = 20% after exposure to an occupational agent, including 357 subjects exposed by the realistic method, 108 using the closed-circuit method and 31 by both methods. For immediate reactions, 18 of 95 (19%) showed changes in FEV1 of > or = 30% with the closed-circuit method, whereas a significantly larger proportion, i.e. 77 of 200 (38.5%), showed such changes using the realistic method. As regards nonimmediate reactions, changes in FEV1 of > or = 30% occurred in 16 of 43 (37%) cases with the closed-circuit method as compared to a larger proportion, i.e. 87 of 180 (48%) cases, using the realistic method. This favourable effect was significantly more pronounced in workers with higher levels of bronchial hyperresponsiveness to methacholine. It is concluded that, for agents that can be generated using the closed-circuit method, use of such apparatus results in a smaller proportion of exaggerated bronchoconstriction than does the realistic method, this being particularly true for low-molecular weight agents.

What is the respiratory retention of inhaled hexamethylene di-isocyanate?

Isocyanates are a frequent cause of occupational asthma. Specific inhalation challenges are often required to confirm the diagnosis. The inhaled concentration has to be assessed during this procedure. However, the respiratory retention of di-isocyanate has not, to the authors knowledge, been evaluated in humans. The existence of a closed-circuit apparatus, designed to carry out these challenges, makes it possible to assess the dose. The respiratory retention of hexamethylene di-isocyanate (HDI) generated in vapour form, in both normal subjects (n=4) and subjects referred for the investigation of occupational asthma due to HDI in whom the diagnosis was excluded (n=5), was assessed. The latter group included four subjects with nonoccupational asthma. The HDI was generated at concentrations varying 5.1-15.2 ppb. The expired concentrations of HDI during such challenges varied 1.4-5.3 ppb. Therefore, the respiratory retention was 61-90%. To conclude, the majority of inhaled hexamethylene di-isocyanate vapour is retained within the airways and/on lung parenchyma.

Computerized equipment for the delivery of inhaled doses of solid particles in specific bronchial challenge.

An apparatus to generate solid particles was tested for use in diagnosing occupational asthma. This equipment measures the inhaled dose of dry particles during specific inhalation challenge. It includes an aerosol generator, a cyclone type particle size selector, and an inhalation chamber to which a patient breathing at tidal volume can be connected for the test. It is fully controlled by a standard personal computer in automatic mode, acting on the flow rate and the aerosol generator to maintain the concentration at a fixed value, usually 3 mg/m3. The dose of aerosol delivered to the patient was calculated from the aerosol concentration, and the inhaled volume was calculated by integration of the corresponding signals. The coefficient of variation for this measurement was estimated to be 12%. The mass median aerodynamic diameter (MMAD) of aerosol inside the inhalation chamber was measured for three substances: lactose, wheat flour, and buckwheat flour. The MMAD of the aerosol inside the chamber was also estimated from the particle size distribution of the raw powder. The relative difference between the measured MMAD and the calculated value was less than 15%. The corresponding relative difference between the measured geometrical SD and the calculated value was found to be less than 26%.

Determinants of the bronchial response to high molecular weight occupational agents in a dry aerosol form.

In occupational challenge tests with isocyanate vapours, bronchial responsiveness is determined by the total dose rather than the concentration or duration of exposure. Whether the same applies for high molecular weight (HMW) agents in powder form is unknown. The aim of this study was to determine whether the total dose of HMW agents in powder form is responsible for the immediate reaction documented in specific challenge tests. Included in the study were nine subjects (seven males and two females) with a diagnosis of occupational asthma proved by specific challenge tests carried out on a preliminary visit. Two challenge tests (using a closed-circuit exposure chamber) were performed at an interval of 2 weeks; the concentrations administered in a random order on these two visits were half and double the one that had caused a 20% fall in forced expiratory volume in one second (FEV1) on a preliminary visit. The duration of exposure was adjusted until a significant fall in FEV1 (target of 20%) occurred. The two concentrations obtained were significantly different, by 2.07+/-0.36-fold (SD). The observed durations of exposure leading to a 20% fall in FEV1 on the two visits also differed significantly by 0.46+/-0.32-fold. Consequently, the cumulative efficient doses were not significantly different between the two visits: 12+/-5.4 and 9+/-5 mg x mL(-1) x min(-1), respectively. The corresponding cumulative dose ratio was 0.96+/-0.61. The expected duration of exposure (10.8+/-24 min) was not significantly different from the observed duration (5.4+/-9 min). The mean and 95% confidence interval for the difference in concentration between the two visits was 1.83-fold (1.48-2.21). In conclusion, the total dose rather than the concentration or duration of exposure per se determines bronchial responsiveness to high molecular weight agents in powder form.

Closed-circuit apparatus for specific inhalation challenges with an occupational agent, formaldehyde, in vapor form.

Specific inhalation challenges are an important tool for confirming occupational asthma. In recent years, we have described two closed-circuit apparatuses that allow exposure to stable and controlled concentrations of particles and isocyanate gases. More recently, we developed a similar apparatus that generates chemicals in vapor form. The aim of this work is to describe its performance in the specific case of formaldehyde. This instrument is made of four parts: a generator as such, an exposure chamber, a monitor, and an automated regulatory system. This apparatus was assessed in four subjects suspected of having formaldehyde-induced asthma or alveolitis. The concentrations of formaldehyde were increased from 0.5 to 1 mg/m3 to 3 mg/m3 keeping the concentration at a value of 3 mg/m3 or less (threshold limit value). The dispersion of obtained values by comparison with the median data (6 values) was as follows: maximum value, 12 to 84%; minimum value, 20 to 58%; interquartile range, 0.13 to 0.9 mg/m3. We observed that target concentrations took a few minutes to be reached, but, once they were obtained, delivered concentrations were stable. The new vapor-delivery apparatus allows us to obtain concentrations of formaldehyde that are close to target concentrations with an acceptable dispersion of values around target concentration. Its use should be extended to other chemicals besides formaldehyde.

Occupational asthma due to formaldehyde resin dust with and without reaction to formaldehyde gas.

We report the cases of three subjects who developed asthma after being exposed to formaldehyde dust or gas. For two subjects, specific bronchial provocation tests with formaldehyde gas did not cause significant bronchoconstriction, whereas exposure to formaldehyde resin dust did. One subject experienced asthmatic reaction after being exposed to formaldehyde resin dust and gas. These findings suggest that the physical and chemical properties of formaldehyde are relevant to its likelihood of causing asthma.

Response to isocyanates: effect of concentration, duration of exposure, and dose.

There is no information on the relative role of dose, concentration, and duration of exposure in determining the magnitude of the bronchial response in subjects with isocyanate-induced asthma. Four subjects with asthma induced by toluene diisocyanate (TDI) were challenged using a recently described closed-circuit exposure chamber in which stable concentrations of TDI monomer can be generated. Each subject was challenged using various concentrations and durations of exposure on separate days. They were all exposed on three to four occasions to the same dose that had been shown to cause a 20% fall in FEV1 at a concentration of 15 ppb (DR15ppb) by varying the concentration (5, 10, 15, and 20 ppb) and durations (1 to 90 min), making sure that the total dose (concentration x duration) remained constant. They were also exposed to lower total doses by modifying the concentration and the duration on the remaining visits. Exposing subjects to the same DR15 ppb by modifying the concentration or the duration resulted in falls in FEV1 > or = 20%, except in one instance. Exposing subjects to doses lower than DR15 ppb, even at higher concentrations or for longer periods than in the challenges used for obtaining the DR15 ppb always caused falls in FEV1 < 20%. We conclude that the main determinant of bronchial responsiveness to TDI is not concentration nor duration of exposure per se but the product of both factors, that is, total dose.

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.

Validation of an exposure system to particles for the diagnosis of occupational asthma.

STUDY OBJECTIVE: We previously described a closed-circuit system for exposure to particles in humans. This system has three components: a particle generator, an exposure chamber connected to an orofacial mask, and monitors. We describe results of challenges in 56 subjects who underwent challenges with the apparatus using occupational sensitizers in particles. SUBJECTS: Fifty-six consecutive subjects referred for the investigation of occupational asthma to occupational sensitizers in particles were included. The agents were the following: flour and grains (n = 19), cedar (n = 10), psyllium (n = 9), guar gum (n = 9), drugs (n = 3), persulfate (n = 2), and miscellaneous (n = 4). INTERVENTION: The duration of exposure was progressive and varied from one breath to a maximum of 180 min depending on the reaction. When no significant fall in FEV1 occurred after exposure with the aerosolization device, the standard approach of tipping particles from one tray to another was used. RESULTS: Twenty-nine subjects (52 percent) had a significant (greater than or equal to 20 percent) fall in FEV1 after exposure. This includes 18 subjects with isolated immediate reactions, four with dual asthmatic reactions, and two with atypical reactions. In 20/24 instances (83 percent), the percentage of fall in FEV1 did not exceed 30 percent, thus showing that dose-response curves can generally be obtained in a safe way. In all instances except one (26/27 cases), subsequent exposures using the traditional method did not result in significant falls in FEV1. CONCLUSION: This new procedure results in safe tests in terms of the percentage of changes in FEV1 during the immediate reactions and very rare false-negative challenges.

Update on an exposure system for particles in the diagnosis of occupational asthma.

We have previously designed a system for exposure to particles and described the preliminary results in 20 subjects exposed to occupational sensitizers in powder form (Cloutier Y, et al. - Eur Respir J, 1989; 2: 769). Modifications have been made to the particles generator, exposure chamber and sampling ports. Furthermore, in order to improve the stability of concentrations in the exposure chamber and to make the system easy to operate by a technician, it has been completely automated using closed-loop feedback regulated by a computer program.

Closed-circuit methodology for inhalation challenge tests with isocyanates.

The diagnosis of isocyanate-induced occupational asthma can be made by exposing subjects to isocyanates in small challenge rooms. There are, however, several pitfalls inherent in this procedure. Isocyanate concentrations may not remain stable throughout the exposure and may exceed the recommended TLV ceiling of 20 ppb. This can induce irritant or unduly severe bronchial reactions. To overcome these problems, a closed-circuit apparatus for generating isocyanates in a gaseous form was developed; it was assessed in 20 subjects suspected of having isocyanate-induced asthma. Subjects were tested using both the small challenge room method and the new closed-circuit method in a randomized sequential way. Isocyanate concentrations were more stable with the closed-circuit apparatus than with the challenge room method (mean of individual variance of 6.3 and 61.8, respectively; p less than 0.001). The percentage of the total exposure time during which concentrations were above 20 ppb was reduced from 11.3 to 4.5% (p less than 0.001). The two methods yielded the same number of positive and negative responses, except for one subject who did not have a positive reaction when tested with the challenge room method. The pattern and magnitude of asthmatic reactions were similar for both methods. However, the duration of exposure was shorter with the challenge room method than with the closed-circuit methods (p = 0.04).

New methodology for specific inhalation challenges with occupational agents in powder form.

Numerous agents in powder form (wood dust, flour, antibiotics, drugs, etc.) can cause occupational asthma. The diagnosis is generally confirmed by specific inhalation challenges in a special challenge room. There are several pitfalls to the procedure: 1) subjects may be exposed to high concentrations of particles; the concentrations of particles may be higher than the threshold limit value-short term exposure level (TLV-STEL), possibly resulting in severe or irritant reactions; 2) the exposure is erratic. To overcome these problems, a new device for aerosolization of powders has been developed. This apparatus consists of three parts: a particles generator, an aerosol delivery system connected to an orofacial mask, and monitors - a photometer and a cascade impactor. Information on the concentration and size distribution of inhaled particles can therefore be obtained. We performed specific inhalation challenges with this apparatus on 20 subjects suspected of having occupational asthma. The concentration of particles was generally below or close to the TLV-STEL and information was obtained on the proportion of particles with a diameter less than 10 mu. Falls in forced expiratory volume in one second (FEV1) were progressive with each increase in the duration of exposure. The five subjects who had negative reactions to exposure were asked to tip the relevant product from one tray to another in the traditional realistic way. All had negative responses. We conclude that this new procedure offers advantages over the traditional method as it gives information on the concentration and size distribution of inhaled particles and makes the drawing of a dose-response curve possible, both of which may improve the safety and accuracy of the test.

Acute exposure to sawdust does not alter airway calibre and responsiveness to histamine in asthmatic subjects.

We investigated the effects of particles of sawdust delivered through a special device at known concentrations (close to the threshold limit value-short term exposure limit (TLV-STEL) of 10 mg.m-3) on FEV1 and PC20 in 12 asthmatic subjects free of clinical sensitization to this product. Subjects were studied over two days (day 1: exposure to sawdust; day 2: sham exposure) in random order with a maximum interval of 1 week. On each day, after the assessment of spirometry and PC20, subjects underwent exposure to sawdust or sham exposure. Sawdust was inhaled for a total of 30 min at average concentrations varying from 8.0 to 19.3 mg.m-3 (mean = 11.5 mg.m-3). Twenty-five to 39.7% (mean = 34.6%) of inhaled particles had a diameter less than 10 mu (diameter allowing deposition in the trachea and lower respiratory tract). At the end of each period of exposure, FEV1 was assessed. After recovery, the second PC20 was obtained. Serial measurements of FEV1 were carried out every hour for up to 6 h after the end of exposure. At that time, PC20 was reassessed. Only one subject showed an acute bronchoconstriction immediately after exposure to sawdust (maximum fall of 14% in FEV1) with complete recovery 10 min later. Overall, inhalation of sawdust did not modify PC20 by comparing the mean result of the first test with the second and the third assessments. Also, the mean changes in PC20 at each interval after exposure to sawdust were not significantly different from the variations in PC20 on the sham day.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficiency of cold hardiness induction by desiccation stress in four winter cereals.

A number of defined desiccation treatments without low temperature exposure were able to induce freezing tolerance in 20 cultivars of winter cereals. A maximal degree of freezing tolerance was induced in epicotyls at 24 degrees C in 24 hours at 40% relative humidity in rye and wheat, 7 days at 54% RH in barley, and 4 days at 70% RH in oats. Freezing tolerance was not correlated to water content of the plants after desiccation treatment but was related to the genetic capacity of the cultivars to frost harden. Levels of freezing tolerance induced by desiccation were similar to those induced by cold acclimation in rye and wheat, but considerably less in barley and oats. This is associated with a more rapid desiccation injury in barley and oats, precluding the completion of the hardening process.