Effects by inhalation of abundant fragrances in indoor air - An overview

Odorous compounds (odors) like fragrances may cause adverse health effects. To assess their importance by inhalation, we have reviewed how the four major abundant and common airborne fragrances (α-pinene (APN), limonene (LIM), linalool (LIL), and eugenol (EUG)) impact the perceived indoor air quality as odor annoyance, sensory irritation and sensitization in the airways. Breathing and cardiovascular effects, and work performance, and the impact in the airways of ozone-initiated gas- and particle phase reactions products have also been assessed. Measured maximum indoor concentrations for APN, LIM and LIL are close to or above their odor thresholds, but far below their thresholds for sensory irritation in the eyes and upper airways; no information could be traced for EUG. Likewise, reported risk values for long-term effects are far above reported indoor concentrations. Human exposure studies with mixtures of APN and LIM and supported by animal inhalation models do not support sensitization of the airways at indoor levels by inhalation that include other selected fragrances. Human exposure studies, in general, indicate that reported lung function effects are likely due to the perception rather than toxic effects of the fragrances. In general, effects on the breathing rate and mood by exposure to the fragrances are inconclusive. The fragrances may increase the high-frequency heart rate variability, but aerosol exposure during cleaning activities may result in a reduction. Distractive effects influencing the work performance by fragrance/odor exposure are consistently reported, but their persistence over time is unknown. Mice inhalation studies indicate that LIM or its reaction mixture may possess anti-inflammatory properties. There is insufficient information that ozone-initiated reactions with APN or LIM at typical indoor levels cause airway effects in humans. Limited experimental information is available on long-term effects of ozone-initiated reaction products of APN and LIM at typical indoor levels.

Airway irritation, inflammation, and toxicity in mice following inhalation of metal oxide nanoparticles

Metal oxide nanoparticles are used in a broad range of industrial processes and workers may be exposed to aerosols of the particles both during production and handling. Despite the widespread use of these particles, relatively few studies have been performed to investigate the toxicological effects in the airways following inhalation. In the present study, the acute (24 h) and persistent (13 weeks) effects in the airways after a single exposure to metal oxide nanoparticles were studied using a murine inhalation model. Mice were exposed 60 min to aerosols of either ZnO, TiO₂, Al₂O₃ or CeO₂ and the deposited doses in the upper and lower respiratory tracts were calculated. Endpoints were acute airway irritation, pulmonary inflammation based on analyses of bronchoalveolar lavage (BAL) cell composition, DNA damage assessed by the comet assay and pulmonary toxicity assessed by protein level in BAL fluid and histology. All studied particles reduced the tidal volume in a concentration-dependent manner accompanied with an increase in the respiratory rate. In addition, ZnO and TiO₂ induced nasal irritation. BAL cell analyses revealed both neutrophilic and lymphocytic inflammation 24-h post-exposure to all particles except TiO₂. The ranking of potency regarding induction of acute lung inflammation was Al₂O₃ = TiO₂<CeO₂ ≪ ZnO. Exposure to CeO₂ gave rise to a more persistent inflammation; both neutrophilic and lymphocytic inflammation was seen 13 weeks after exposure. As the only particles, ZnO caused a significant toxic effect in the airways while TiO₂ gave rise to DNA-strand break as shown by the comet assay.

Mechanism of action of lung damage caused by a nanofilm spray product

Inhalation of waterproofing spray products has on several occasions caused lung damage, which in some cases was fatal. The present study aims to elucidate the mechanism of action of a nanofilm spray product, which has been shown to possess unusual toxic effects, including an extremely steep concentration-effect curve. The nanofilm product is intended for application on non-absorbing flooring materials and contains perfluorosiloxane as the active film-forming component. The toxicological effects and their underlying mechanisms of this product were studied using a mouse inhalation model, by in vitro techniques and by identification of the binding interaction. Inhalation of the aerosolized product gave rise to increased airway resistance in the mice, as evident from the decreased expiratory flow rate. The toxic effect of the waterproofing spray product included interaction with the pulmonary surfactants. More specifically, the active film-forming components in the spray product, perfluorinated siloxanes, inhibited the function of the lung surfactant due to non-covalent interaction with surfactant protein B, a component which is crucial for the stability and persistence of the lung surfactant film during respiration. The active film-forming component used in the present spray product is also found in several other products on the market. Hence, it may be expected that these products may have a toxicity similar to the waterproofing product studied here. Elucidation of the toxicological mechanism and identification of toxicological targets are important to perform rational and cost-effective toxicological studies. Thus, because the pulmonary surfactant system appears to be an important toxicological target for waterproofing spray products, study of surfactant inhibition could be included in toxicological assessment of this group of consumer products.

Pulmonary toxicity following exposure to a tile coating product containing alkylsiloxanes. A clinical and toxicological evaluation

CONTEXT

Coating products are widely used for making surfaces water and dirt repellent. However, on several occasions the use of these products has been associated with lung toxicity.

OBJECTIVE

In the present study, we evaluated the toxic effects of an aerosolized tile-coating product.

METHODS

Thirty-nine persons, who reported respiratory and systemic symptoms following exposure to the tile-coating product, were clinically examined. The product was analysed chemically and furthermore, the exposure scenario was reconstructed using a climate chamber and the toxicological properties of the product were studied using in vivo and by in vitro surfactometry.

RESULTS

The symptoms developed within few hours and included coughing, tachypnoea, chest pain, general malaise and fever. The physical examination revealed perihilar lung infiltrates on chest radiograph and reduced blood oxygen saturation. The acute symptoms resolved gradually within 1-3 days and no delayed symptoms were observed. By means of mass spectrometry and X-ray spectroscopy, it was shown that the product contained non-fluorinated alkylsiloxanes. The exposure conditions in the supermarket were reconstructed under controlled conditions in a climate chamber and particle and gas exposure levels were monitored over time allowing estimation of human exposure levels. Mice exposed to the product developed symptoms of acute pulmonary toxicity in a concentration-and time-dependent manner. The symptoms of acute pulmonary toxicity likely resulted from inhibition of the pulmonary surfactant function as demonstrated by in vitro surfactometry. Among these patients only a partial association between the level of exposure and the degree of respiratory symptoms was observed, which could be because of a high inter-individual difference in sensitivity and time-dependent changes in the chemical composition of the aerosol.

CONCLUSION

Workers need to cautiously apply surface coating products because the contents can be highly toxic through inhalation, and the aerosols can disperse to locations remote from the worksite and affect bystanders.

Experiences from occupational exposure limits set on aerosols containing allergenic proteins

Occupational exposure limits (OELs) together with determined airborne exposures are used in risk assessment based managements of occupational exposures to prevent occupational diseases. In most countries, OELs have only been set for few protein-containing aerosols causing IgE-mediated allergies. They comprise aerosols of flour dust, grain dust, wood dust, natural rubber latex, and the subtilisins, which are proteolytic enzymes. These aerosols show dose-dependent effects and levels have been established, where nearly all workers may be exposed without adverse health effects, which are required for setting OELs. Our aim is to analyse prerequisites for setting OELs for the allergenic protein-containing aerosols. Opposite to the key effect of toxicological reactions, two thresholds, one for the sensitization phase and one for elicitation of IgE-mediated symptoms in sensitized individuals, are used in the OEL settings. For example, this was the case for flour dust, where OELs were based on dust levels due to linearity between flour dust and its allergen levels. The critical effects for flour and grain dust OELs were different, which indicates that conclusion by analogy (read-across) must be scientifically well founded. Except for subtilisins, no OEL have been set for other industrial enzymes, where many of which are high volume chemicals. For several of these, OELs have been proposed in the scientific literature during the last two decades. It is apparent that the scientific methodology is available for setting OELs for proteins and protein-containing aerosols where the critical effect is IgE sensitization and IgE-mediated airway diseases.

Acute and subchronic airway inflammation after intratracheal instillation of quartz and titanium dioxide agglomerates in mice

This study investigated the acute and subchronic inflammatory effects of micrometer-size (micro-size) and nanometer-size (nano-size) particles after intratracheal (i.t.) installation in mice. The role of the type of compound, polymorphism, and size of the particles was investigated. Studied compounds were the two micro-size reference quartzes, SRM1878a and DQ12, a micro- and nano-size rutile titanium dioxide (TiO2), a nano-size anatase, and an amorphous TiO2. Particles were administered by a single i.t. instillation in mice at a fixed dose of 5, 50, and 500 micrograms, respectively. Inflammation was evaluated from the bronchoalveolar lavage fluid (BALF) content of inflammatory cells, the cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6), as well as from lung histology. Evaluations were at 24 h (acute effects) and 3 months (subchronic effects) after instillations. Both types of quartz induced a dose-dependent acute increase of neutrophils, IL-6, and total protein in BALF. Limited subchronic inflammation was observed. All types of TiO2 induced a dose-dependent acute increase of neutrophils in BALF. In the acute phase, micro- and nano-size rutile and nano-size amorphous TiO2 induced elevated levels of IL-6 and total protein in BALF at the highest dose. At the nano-size rutile and amorphous TiO2, subchronic lung inflammation was apparent from a dose-dependent increase in BALF macrophages. Histology showed little inflammation overall. The two types of quartz showed virtually similar inflammatory effects. Nearly similar effects were observed for two sizes of rutile TiO2. Differences were seen between the different polymorphs of nano-size TiO2, with rutile being the most inflammogenic and amorphous being the most potent in regard to acute tissue damage.

Non-cancer effects of formaldehyde and relevance for setting an indoor air guideline

There is considerable recent focus and concern about formaldehyde (FA). We have reviewed the literature on FA with focus on chemosensory perception in the airways and lung effects in indoor environments. Concentrations of FA, both personal and stationary, are on average in the order of 0.05 mg/m(3) or less in Europe and North America with the exception of new housing or buildings with extensive wooden surfaces, where the concentration may exceed 0.1 mg/m(3). With the eye the most sensitive organ, subjective irritation is reported at 0.3-0.5 mg/m(3), which is somewhat higher than reported odour thresholds. Objective effects in the eyes and airways occur around 0.6-1 mg/m(3). Dose-response relationships between FA and lung function effects have not been found in controlled human exposure studies below 1 mg/m(3), and epidemiological associations between FA concentrations and exacerbation of asthma in children and adults are encumbered by complex exposures. Neither experimental nor epidemiological studies point to major differences in susceptibility to FA among children, elderly, and asthmatics. People with personal trait of negative affectivity may report more symptoms. An air quality guideline of 0.1 mg/m(3) (0.08 ppm) is considered protective against both acute and chronic sensory irritation in the airways in the general population assuming a log normal distribution of nasal sensory irritation.

Carcinogenicity of occupational nickel exposures: an evaluation of the epidemiological evidence

The health effects documented in recent epidemiological studies of nickel-exposed workers relate to past exposures, mostly of unknown magnitude and unknown nickel speciation. Major studies have been carried out at nickel smelters and refineries. Although each study suffers from some deficiencies, as is common in such retrospective studies, the findings in concert strongly indicate that nickel emitted from the calcining and sintering operations is a potent carcinogen resulting in nasal and pulmonary cancers. Some risk appears to be present in other refinery operations, such as Orford furnace, copper and nickel sulfate, and crushing departments, and one study has suggested a risk associated with soluble nickel compounds in the electrolysis department, although this finding has not been confirmed. Only one study demonstrated an exposure-response relationship, which, however, was not statistically significant. Other studies showed a relationship between increased exposure time and augmented cancer risk. In nickel-using industries, no excess cancer related to nickel exposures has been demonstrated beyond doubt; concurrent exposures to other potential carcinogens constitute a confounding variable that makes interpretation difficult. However, the studies have not excluded that a cancer hazard may be present outside the nickel-producing facilities. Further, case-referent studies of respiratory cancers suggest that a nickel-related etiology may well exist in the nickel-using industries. As the exact identity of the carcinogenic form or forms of nickel remains unknown, exposure to all nickel compounds should be kept as low as reasonably achievable.

Lung damage in mice after inhalation of nanofilm spray products: the role of perfluorination and free hydroxyl groups

Exposures to two commercial nanofilm spray products (NFPs), a floor sealant (NFP 1) and a coating product for tiles (NFP 2), were investigated for airway irritation, airway inflammation, and lung damage in a mouse inhalation model. The particle exposure was characterized by particle number, particle size distribution, and gravimetric analysis. BALB/cJ mice were exposed for 60 min to the aerosolized products at 3.3-60 mg/m(3) (10(5)-10(6) fine particles/cm(3)) measured in the breathing zone of the mice. Lung inflammation and lung damage were assessed by study of bronchoalveolar lavage fluid (BALF) cytology, protein in BALF, and histology. Mass spectral analysis showed that NFP 1 and NFP 2 contained hydrolysates and condensates of a perfluorosilane and alkylsilane, respectively. NFP 1 induced a concentration-dependent decrease of the tidal volume lasting for at least 1 day. Exposure concentrations above 16.1 mg/m(3) (2.1 x 10(6) fine particles/cm(3)) gave rise to significant increases of protein level in BALF and reduced body weight, and histological examination showed atelectasis, emphysema, and hemorrhages. A narrow interval between the no-effect level (16.1 mg/m(3)) and the lethal concentrations (18.4 mg/m(3)) was observed. The alkylsilane-based product (NFP 2) had no effect at the concentrations studied. Experiments with different types of perfluorinated silanes and alkylsiloxanes showed that the toxic effects did not arise solely from the perfluorination. The number of free hydroxyl groups in the silanes/alkylsiloxanes was also critical for the toxicity.

Time-response relationship of nano and micro particle induced lung inflammation. Quartz as reference compound

An increasing number of engineered particles, including nanoparticles, are being manufactured, increasing the need for simple low-dose toxicological screening methods. This study aimed to investigate the kinetics of biomarkers related to acute and sub-chronic particle-induced lung inflammation of quartz. Mice were intratracheal instilled with 50 µg of microsized or nanosized quartz. Acute inflammation was assessed 1, 2, 4, 8, 16 or 48 hours post exposure, whereas sub-chronic inflammation was investigated 3 months after exposure. Markers of acute inflammation in the bronchoalveolar lavage fluid (BALF) were neutrophils (PMN), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, macrophage inflammatory protein-2 (MIP-2), keratinocyte derived chemokine (KC) and total protein, which were all close to maximum 16 hours post instillation. No major differences were seen in the time-response profiles of nano- and micro-sized particles. The potency of the two samples cannot be compared; during the milling process, a substantial part of the quartz was converted to amorphous silica and contaminated with corundum. For screening, BALF PMN, either TNF-α or IL-1β at 16 hours post instillation may be useful. At 3 months post instillation, KC, PMN and macrophages were elevated. Histology showed no interstitial inflammation three months post instillation. For screening of sub-chronic effects, KC, PMN, macrophages and histopathology is considered sufficient.

Desensitization of ovalbumin-sensitized mice by repeated co-administrations of di-(2-ethylhexyl) phthalate and ovalbumin

Background

The plasticizer di-(2-ethylhexyl) phthalate (DEHP) has been shown to stimulate a non-allergy related immune response with increased levels of IgG1 and IgG2a, but not IgE, after co-administration with the model allergen ovalbumin (OVA) in mice. In mice, decreased IgG1 and increased IgG2a have been associated with the development of mucosal tolerance towards inhaled allergens. As DEHP selectively promote formations of IgG1 and IgG2a without stimulating the IgE response, it was hypothesized that DEHP may suppress an established IgE mediated allergic response. Mice pre-sensitised to OVA were repeatedly co-exposed to DEHP and OVA and the effects were evaluated on the levels of OVA-specific antibodies, ex vivo cytokine levels and the degree of lung inflammation after challenge with an OVA aerosol.

Findings

Compared to the OVA-sensitised control mice, multiple co-exposures to DEHP+OVA reduced the IgG1 level and reduced the IgE/IgG2a ratio. This suggests that DEHP may attenuate allergic sensitisation, as the IgE/IgG2a ratio has been shown to correlate with the degree of anaphylaxis. Nevertheless, no effect of DEHP exposures was seen on inflammatory cells in bronchoalveolar lavage fluid and on cytokine levels in spleen cell culture.

Conclusion

Data from humane and murine studies suggest that DEHP may attenuate the allergic response. More studies are necessary in order to assess the size of this effect and to rule out the underlying mechanism.

Nano titanium dioxide particles promote allergic sensitization and lung inflammation in mice

The purpose of this study was to investigate whether photocatalytic TiO₂ nanoparticles have adjuvant effect, when administered in combination with ovalbumin (OVA) in mice. Mice were immunized via intraperitoneal injections of OVA, OVA + TiO₂ or OVA + Al(OH)₃ and challenged with aerosols of OVA. At the end of the study, serum was analysed for content of OVA-specific IgE, IgG1 and IgG2a antibodies, and the bronchoalveolar lavage fluid (BALF) was analysed for content of inflammatory cells and levels of interleukin (IL)-4, IL-5, IL-10 and interferon-γ. The TiO₂ particles promoted a Th2 dominant immune response with high levels of OVA-specific IgE and IgG1 in serum and influx of eosinophils, neutrophils and lymphocytes in BALF. The TiO₂ particles induced a significantly higher level of OVA-specific IgE than the standard adjuvant Al(OH)₃. However, the two substances were comparable regarding the level of eosinophilic inflammation and interleukins present in BALF.

Structure-activity relationship of immunostimulatory effects of phthalates

Background

Some chemicals, including some phthalate plasticizers, have been shown to have an adjuvant effect in mice. However, an adjuvant effect, defined as an inherent ability to stimulate the humoral immune response, was only observed after exposure to a limited number of the phthalates. An adjuvant effect may be due to the structure or physicochemical characteristics of the molecule. The scope of this study was to investigate which molecular characteristics that determine the observed adjuvant effect of the most widely used phthalate plasticizer, the di-(2-ethylhexyl) phthalate (DEHP), which is documented as having a strong adjuvant effect. To do so, a series of nine lipophilic compounds with structural and physicochemical relations to DEHP were investigated.

Results

Adjuvant effect of phthalates and related compounds were restricted to the IgG1 antibody formation. No effect was seen on IgE. It appears that lipophilicity plays a crucial role, but lipophilicity does not per se cause an adjuvant effect. In addition to lipophilicity, a phthalate must also possess specific stereochemical characteristics in order for it to have adjuvant effect.

Conclusion

The adjuvant effect of phthalates are highly influenced by both stereochemical and physico-chemical properties. This knowledge may be used in the rational development of plasticizers without adjuvant effect as well as in the design of new immunological adjuvants.

Acute airway effects of ozone-initiated d-limonene chemistry: importance of gaseous products

There are concerns about ozone-initiated chemistry, because the formation of gaseous oxidation products and ultrafine particles may increase complaints, morbidity and mortality. Here we address the question whether the gaseous products or the ultrafine particles from the ozone-initiated chemistry of limonene, a common and abundant indoor pollutant, cause acute airway effects. The effects on the airways by d-limonene, a ca. 16s old ozone/d-limonene mixture, and clean air were evaluated by a mice bioassay, from which sensory irritation of the upper airways, airflow limitation, and pulmonary irritation can be obtained. A denuder was inserted to separate the ultrafine particles from the gaseous products prior to the exposure chamber. Reduction of mean respiratory frequency (>30%) and 230% increase of time of brake were observed without denuder, during 30min exposure, to the ozonolyzed d-limonene mixture, which are indicative of prominent sensory effects. The initial concentrations (ppm) were 40 d-limonene and 4 ozone. The exposure concentrations (ppm) were about 35 d-limonene and 0.05 ozone. Formaldehyde and residual d-limonene, the salient sensory irritants, accounted for up to three-fourth of the sensory irritation. The upper airway effects reversed to baseline upon cessation of exposure. An effect on the conducting airways was also significant, which did not reverse completely upon cessation. Airway effects were absent with the denuder inserted, which did not alter the size distribution of ultrafine particles ( approximately 10mg/m(3)), significantly. The result was statistically indistinguishable from clean dry air. It is concluded that ultrafine particles that are generated from ozone-initiated d-limonene chemistry and denuded are not causative of sensory effects in the airways.

Do indoor chemicals promote development of airway allergy?

Allergic asthma has increased worldwide in the industrialized countries. This review evaluates whether the major groups of indoor chemical exposures possess allergy-promoting (adjuvant) effects; formaldehyde was excluded, because of the size of the literature. Volatile organic compounds (VOCs) are used as an example of gases and vapors. The precipitation of asthmatic symptoms by VOC exposures is probably because of VOC levels considerably above typical indoor levels, or VOCs may be a surrogate for exposure to allergens, combustion products or dampness. Indoor particles possessed adjuvant effects in animal studies and allergy-promoting effects in humans. Quaternary ammonium compounds may possess adjuvant effects in animal studies and promoted sensitization in humans in occupational settings. The use of cleaning agents, anionic and non-ionic surfactants are not considered to possess an important adjuvant effect in the general population. Regarding phthalate exposures, results from animal and epidemiological studies were found to be discordant. There is little evidence that the indoor chemicals evaluated possess important adjuvant effects. If buildings are kept clean, dry and free of combustion products, the important question may be would it be profitable to look for lifestyle factors and non-chemical indoor exposures in order to abate airway allergy?

PRACTICAL IMPLICATIONS

Indoor chemicals (pollutants) have been accused to promote development of airway allergy by adjuvant effects. In this review, we evaluated the scientific literature and found little support for the supposition that indoor chemicals possess important adjuvant effects. This rises the question: would it be profitable for abatement of airway allergy to look for non-chemical indoor exposures, including lifestyle factors, and exposures to allergens, microorganisms, including vira, and their interactions?

Organic compounds in office environments - sensory irritation, odor, measurements and the role of reactive chemistry

Abstract Sensory irritation and odor effects of organic compounds in indoor environments are reviewed. It is proposed to subdivide volatile organic compounds (VOCs) into four categories: (i) chemically non-reactive, (ii) chemically 'reactive', (iii) biologically reactive (i.e. form chemical bonds to receptor sites in mucous membranes) and (iv) toxic compounds. Chemically non-reactive VOCs are considered non-irritants at typical indoor air levels. However, compounds with low odor thresholds contribute to the overall perception of the indoor air quality. Reported sensory irritation may be the result of odor annoyance. It appears that odor thresholds for many VOCs probably are considerably lower than previously reported. This explains why many building materials persistently are perceived as odorous, although the concentrations of the detected organic compounds are close to or below their reported odor thresholds. Ozone reacts with certain alkenes to form a gas and aerosol phase of oxidation products, some of which are sensory irritants. However, all of the sensory irritating species have not yet been identified and whether the secondary aerosols (ultrafine and fine particles) contribute to sensory irritation requires investigation. Low relative humidity may exacerbate the sensory irritation impact. Practical Implications Certain odors, in addition to odor annoyance, may result in psychological effects and distraction from work. Some building materials continually cause perceivable odors, because the odor thresholds of the emitted compounds are low. Some oxidation products of alkenes (e.g. terpenes) may contribute to eye and airway symptoms under certain conditions and low relative humidity.

IgE-mediated sensitisation, rhinitis and asthma from occupational exposures. Smoking as a model for airborne adjuvants?

OBJECTIVE

Airborne pollutants with adjuvant effect, called airborne adjuvants, may promote IgE-sensitisation and development of allergic airway diseases. Smoking and occupational allergen exposures were reviewed to establish a general and verified framework for hazard identification and risk assessment of adjuvant effects of airborne pollutions.

METHODS

The relative risks and the attributable risks of adjuvant effect of smoking were determined for co-exposures with green coffee and castor beans, ispaghula, senna, psyllium, flour and grain dust, latex, laboratory animals, seafood, enzymes, platinum salts, organic anhydrides, or reactive dyes.

RESULTS

Adjuvant effects of smoking depended on the types of allergen, but not on whether sensitisation or allergy was promoted by atopy-the hereditarily increased ability to increase IgE formation.

CONCLUSION

Promotion of IgE sensitisation in humans and in animals may serve for hazard identification of adjuvant effects. Risk assessment has been based mainly on epidemiological studies, which are sensitive to confounding factors. This highlights the need to develop appropriate animal models for risk assessment.

Adjuvant effect of quaternary ammonium compounds in a murine model

It has been suggested that occupational exposure to quaternary ammonium compounds (QACs) may promote the development of allergic airway diseases. In this study, hazard identifications of the adjuvant effect of cetylpyridinium chloride (CPC), dimethyldioctadecylammonium bromide (DDA), hexadecyltrimethylammonium bromide (HTA), and tetraethylammonium chloride (TEA) were performed in a screening bioassay. Female BALB/c mice were injected subcutaneously with the model allergen ovalbumin (OVA) alone or together with different quantities of one of the QAC test compounds. After one or two boosters, levels of OVA-specific IgE, IgG1 and IgG2a antibodies were measured in sera. CPC and DDA increased IgE and IgG1 antibody production, respectively, compared to the OVA control group, whereas HTA and TEA showed no adjuvant effect. Nevertheless, when TEA was given in combination with DDA, the adjuvant effect was up to six-fold higher than the adjuvant effect of DDA alone. Only DDA had a statistically significant adjuvant effect on IgG2a antibody levels.

Upper airway irritation of terpene/ozone oxidation products (TOPS). Dependence on reaction time, relative humidity and initial ozone concentration

Recently, we reported the formation of unidentified strong upper airway irritants in reaction mixtures of terpenes and ozone. The identified products included aldehydes, ketones and carboxylic acids. Here we report the effects of variation of reaction time, relative humidity and initial ozone concentration on irritant formation in a flow reaction system using R-(+)-limonene and isoprene. Upper airway irritation was measured in mice as reduction of the respiratory rate. For both substances maximum irritation was observed for low humidity (<2% RH)/short time (16-30 s) reaction mixtures, and both moderate humidity ( approximately 32% RH) and longer reaction times (60-90 s) resulted in significantly less irritation. These results suggest that some unidentified intermediates react with water vapor to give less irritating products. Irritation measured at four ozone concentrations (0.5, 1, 2 and 3.5 ppm) using low humidity/short time reaction conditions for limonene (50 ppm) and isoprene (500 ppm) revealed that at 0.5 ppm, irritation was at the same level as that for the pure terpenes, indicating that at 0.5 ppm ozone the combined irritant effect was near the no effect level for the product mixture.

Investigation of the adjuvant and immuno-suppressive effects of benzyl butyl phthalate, phthalic acid and benzyl alcohol in a murine injection model

In a recent study, di-(2-ethylhexyl) phthalate (DEHP) and its metabolite, mono-2-ethylhexyl phthalate, were shown to possess adjuvant effect [Toxicology 169 (2001) 37; Toxicology Letters 125 (2001) 11]. The present study investigates the adjuvant effect of another important commercial phthalate plasticizer, benzyl butyl phthalate (BBP) as well as its degradation products, phthalic acid and benzyl alcohol (BA) in a murine model. The model antigen, ovalbumin (OA), was injected either alone (OA control group), together with one of the test substances (test group) or together with aluminium hydroxide, which served as the positive adjuvant control. The mice were boosted either once or twice with OA before blood was collected and assayed for the content of OA-specific IgE, IgG1 and IgG2a antibodies by ELISA methods. Adjuvant effect was defined as a statistically significant increased antibody level in the test groups compared with the OA control group. Conversely, if the antibody production in a test group was significantly lower than the OA control group, it was deemed to be immunosuppression. This study demonstrated that BBP, in contrast to DEHP, did not possess adjuvant effect. Furthermore, immunosuppression was apparent in the case of BA. The study also demonstrated that if the injections give rise to formation of wounds, it may cause false positive results.

Adjuvant effect of di-n-butyl-, di-n-octyl-, di-iso-nonyl- and di-iso-decyl phthalate in a subcutaneous injection model using BALB/c mice

During the last decades, the prevalence of the allergic airway diseases, asthma and rhinitis, has increased world-wide. Introduction of environmental chemicals with adjuvant effect may play a role in this increase. In the present study, the adjuvant effects of di-n-butyl-, di-n-octyl-, di-iso-nonyl- and di-iso-decyl phthalate are studied in a screening model. Ovalbumin, used as the model antigen, was injected subcutaneously in the neck region of BALB/cJ mice with the selected phthalate in concentrations from 2-2000 microg/ml. Additionally, the mice were boosted once or twice with ovalbumin alone. Immunization with ovalbumin alone, the ovalbumin control group, served as the baseline for antibody production, whereas aluminium hydroxide served as the positive control. The levels of ovalbumin-specific IgE, IgG1 and IgG2a antibodies in sera were determined. Adjuvant effect was accepted to be present if a statistical increase in antibody production occurred in a test group as compared to an ovalbumin control group together with the fulfillment of dose-response relationships. Adjuvant effect varied strongly between the phthalates investigated. Phthalates with 8 or 9 carbon atoms in the alkyl side chains were the stronger adjuvants whereas phthalates with shorter or longer alkyl side chains possessed less adjuvant activity. Adjuvant effects were apparent either from the IgE or the IgG1 response or both, whereas no effect was seen on the IgG2a response. Additional studies with airborne exposure are required to establish whether the hazards also result in a significant risk for the development of allergy in man.

Upper airway and pulmonary effects of oxidation products of (+)-alpha-pinene, d-limonene, and isoprene in BALB/c mice

The oxidation products (OPs) of ozone and the unsaturated hydrocarbons d-limonene, (+)-alpha-pinene, and isoprene have previously been shown to cause upper airway irritation in mice during 30-min acute exposures. This study evaluated the effects of OPs and the hydrocarbons themselves on the upper airways, the conducting airways, and the lungs over a longer exposure period. The time course of development of effects and the reversibility of effects were investigated; in addition, we assessed possible exacerbation of sensory responses of the airways to the unreacted hydrocarbons. Respiratory parameters in male BALB/c mice were monitored via head-out plethysmography. Exposures to OPs or hydrocarbons were for 60 min, followed by a 30-min challenge period with air or hydrocarbon, and a 15-min recovery period with air only. Experiments were also performed where limonene/ozone exposures were separated 6 h from the challenge period. Ozone concentration in the reaction mixture was 3.4 ppm, and concentrations of hydrocarbons were 47 ppm (alpha-pinene), 51 ppm (d-limonene), and 465 ppm (isoprene). Due to reaction, the ozone concentration at the point of exposure was less than 0.35 ppm; exposure to 0.30 ppm ozone for 60 min did not produce effects different from air-exposed control animals. As previously established, upper airway irritation was a prominent effect of OP exposure. In addition, over the longer exposure period we observed the development of airflow limitation that persisted for at least 45 min postexposure. All effects from limonene/ozone exposures were reversible within 6 h. Exposures to OPs did not cause enhanced upper airway irritation during challenge with the hydrocarbons, indicating that a 1-h exposure to OPs did not increase the sensitivity of the upper respiratory system. However, airflow limitation was exacerbated in animals exposed to d-limonene alone immediately following exposure to limonene OPs. These findings suggest that terpene/ozone reaction products may have moderate-lasting adverse effects on both the upper airways and pulmonary regions. This may be important in the context of the etiology or exacerbation of lower airway symptoms in office workers, or of occupational asthma in workers involved in industrial cleaning operations.

IgE-mediated asthma and rhinitis I: a role of allergen exposure?

Exposures to airborne protein antigens, aeroallergens, may cause sensitization with production of Th2-dependent antibodies, including IgE. The IgE antibodies and associated cellular responses are responsible for the allergic airway diseases, allergic rhinitis and allergic asthma, which are increasing in societies with Western life style. Aeroallergens may have different potential to sensitize exposed subjects. Thus, there are only a limited number of important groups of aeroallergens, which are those from house dust mites, cockroaches, pets, pollens, and moulds. Allergy follows to a certain extent the pharmacological/toxicological paradigm of dose-response relationship. Unlike effects of pharmacologically and toxicologically active substances, allergens elicit their adverse effects in a two-stage process. In the first stage the immunologically naïve individual is sensitized to the allergen. In the second stage renewed exposure to the allergen elicits the disease response. Also, high concentrations of aeroallergens may induce immunological tolerance. The scientific literature suggests that many environmental factors contribute to the increase in sensitization and development of airway allergies. Nevertheless, the dose-response relationships apply (within certain limits) both to the sensitization itself and to the exacerbation of the diseases. This suggest that exposure reduction may be one of the methods for reduction of risk, in relation to control of the allergic airway diseases.

Investigation of the adjuvant effect of polyethylene glycol (PEG) 400 in BALB/c mice

In the formulation of peptide- and protein-based drugs, it is important that the pharmaceutical excipients used do not potentiate possible immunogenic properties of the drug substance. Polyethylene glycols (PEGs) are widely used excipients e.g. in parenteralia and in formulations for nasal application. The immunomodulating properties of PEG 400 were investigated in this study using hen egg ovalbumin (OA) as the model immunogen. OA was dissolved in saline, 10% PEG 400 in saline or undiluted PEG 400 and injected subcutaneously into the neck region of BALB/cJ mice. The levels of OA-specific IgE, IgG1 and IgG2a antibodies were measured. The 10% solution of PEG 400 did not have any immunomodulating properties, whereas the undiluted product gave rise to immunosuppression when compared with the saline control. Neither 10% nor the 100% PEG 400 preparation possessed adjuvant activity under the conditions of the study.

Adjuvant and immuno-suppressive effect of six monophthalates in a subcutaneous injection model with BALB/c mice

The prevalence of allergic airway diseases is rapidly increasing in Western Europe and North America. This increase in disease prevalence may be associated with environmental pollutants. The present study investigated the adjuvant and immuno-suppressive effect of a series of monophthalates which are considered to be important metabolites of commonly used phthalate plasticizers. The effects were studied in a screening model. Ovalbumin (OA), used as the model antigen, was injected subcutaneously in the neck region of BALB/cJ mice with or without one of the test substances, mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBnP), mono-n-octyl phthalate (MnOP), mono-2-ethylhexyl phthalate (MEHP), mono-iso-nonyl phthalate (MiNP) or mono-iso-decyl phthalate (MiDP). The levels of OA-specific IgE, IgG1 and IgG2a in sera were measured by ELISA. Immuno-suppressive effect, defined as a statistically significant reduction in IgE or IgG1 antibody production, was observed with MEHP (1000 microg/ml, IgE and IgG1), MnOP (1000 microg/ml, IgE and IgG1), MiNP (1000 microg/ml, IgE and 10 microg/ml, IgG1) and MiDP (100 microg/ml, IgE and IgG1). Adjuvant effect, defined as a statistically significant increase in IgE or IgG1 antibody level, occurred with MEHP (10 microg/ml, IgE), MnOP (100 microg/ml, and 10 microg/ml, IgG1) and MiNP (100 microg/ml, IgE). No statistically significant immune modulating effect was seen with MBnP and MnBP.

Formation of strong airway irritants in mixtures of isoprene/ozone and isoprene/ozone/nitrogen dioxide

We evaluated the airway irritation of isoprene, isoprene/ozone, and isoprene/ozone/nitrogen dioxide mixtures using a mouse bioassay, from which we calculated sensory irritation, bronchial constriction, and pulmonary irritation. We observed significant sensory irritation (approximately 50% reduction of mean respiratory rate) by dynamically exposing the mice, over 30 min, to mixtures of isoprene and O3 or isoprene, O3, and NO2. The starting concentrations were approximately 4 ppm O3 and 500 ppm isoprene (+ approximately 4 ppm NO2. The reaction mixtures after approximately 30 sec contained < 0.2 ppm O3. Addition of the effects of the residual reactants and the identified stable irritant products (formaldehyde, formic acid, acetic acid, methacrolein, and methylvinyl ketone) could explain only partially the observed sensory irritation. This suggests that one or more strong airway irritants were formed. It is thus possible that oxidation reactions of common unsaturated compounds may be relevant for indoor air quality.

Chemical and biological evaluation of a reaction mixture of R-(+)-limonene/ozone: formation of strong airway irritants

The airway irritation of a reaction mixture of R-(+)-limonene and ozone was evaluated by a mouse bioassay in which sensory irritation, bronchoconstriction and pulmonary irritation were measured. Significant sensory irritation (33% reduction of mean respiratory rate) was observed by dynamic exposure of the mice, during 30 min, to a ca. 16 s old reaction mixture of ozone and limonene. The initial concentrations were nominally 4 ppm O3 and 48 ppm limonene. After reaction, the residual O3 was <0.03 ppm. Conventional analytical chemical methods were used to measure the formation of readily identified and stable products. Besides the expected products, 1-methyl-4-acetylcyclohexene (AMCH), 3-isopropenyl-6-oxoheptanal (IPOH), formaldehyde and formic acid, autooxidation products of limonene and a series of compounds including acetone, acrolein and acetic acid, which may or may not be artefacts, were identified. Addition of the sensory irritation effects of the residual reactants and all the identified compounds could not explain the observed sensory irritation effect. This suggests that one or more strong airway irritants were formed. Since limonene is common in the indoor air, and ozone is infiltrated from outdoors and/or produced indoors (e.g., by photocopiers), such oxidation reactions may be relevant for indoor air quality.

Detergents in the indoor environment - what is the evidence for an allergy promoting effect? Known and postulated mechanisms

IgE-mediated allergic diseases, such as asthma and rhinitis seem to be increasing in industrialised societies. One possible explanation for this could be the increased use of more effective and aggressive detergents. The surfactants from these could interfere with the sensitisation process in which specific IgE is formed to ubiquitously occurring environmental allergens. Only sparse data exist in relation to surfactants and allergic sensitization. However, it can be speculated that the strong surfactant properties of some of ingredients used in modem detergents may interfere with some of the intricate cellular interactions taking place along the immunological pathways. These include formation of IL-4 and IL-5 producing T helper lymphocytes type 2 and the B-lymphocyte isotype switch, which leads to production of specific IgE. Candidates for experimental studies of such phenomena on the cellular level are proposed.

Study of adjuvant effect of model surfactants from the groups of alkyl sulfates, alkylbenzene sulfonates, alcohol ethoxylates and soaps

The sodium salts of representatives of anionic surfactants, dodecylbenzene sulfonate (SDBS), dodecyl sulfate (SDS) and coconut oil fatty acids, and a nonionic surfactant, dodecyl alcohol ethoxylate, were studied for adjuvant effect on the production of specific IgE antibodies in mice. The surfactants were injected subcutaneously (sc) in concentrations of 1000, 100, 10 or 1 mg/l, respectively, together with 1 microg of ovalbumin (OVA). In addition, groups of mice received OVA in saline (control group) or in Al(OH)(3) (positive adjuvant control group). After the primary immunization the mice were boosted up to three times with OVA (0.1 microg sc) in saline. OVA-specific IgE antibodies were determined by the heterologous mouse rat passive cutaneous anaphylaxis test. The results were confirmed by a specific ELISA method. After the first booster, the Al(OH)(3) group and the 10 mg/l SDS group showed a statistically significant increase in OVA specific IgE levels. After two boosters, a statistically significant suppression in OVA-specific IgE production occurred with SDS (1000 mg/l), SDBS (1000 and 100 mg/l), coconut soap (1000 mg/l) and the alcohol ethoxylate (10 mg/l). This study suggests that a limited number of surfactants possess an adjuvant effect whereas all surfactants at certain levels can suppress specific IgE production.

Effects of R-(+)- and S-(-)-limonene on the respiratory tract in mice

The effects of airborne R-(+)- and S-(-)- limonene were studied in conscious BALB/c mice by continuous monitoring respiratory rate (f), tidal volume (VT) and mid-expiratory flow rate (VD) during an exposure period of 30 min. Both enantiomers decreasedf from a trigeminal reflex, i.e., due to sensory irritation. The exposure concentration decreasing f by 50% (RD50) in the first 10 min of the exposure period was estimated to be 1,076 ppm for R-(+)-limonene and 1,467 ppm for S-(-)-limonene. Results for sensory irritation of R-(+)-limonene in BALB/c mice and humans are in close agreement. The reported sensory irritation threshold is above 80 ppm in humans while the no-observed-effect level was estimated to be 100 ppm in mice. The enantiomers were devoid of pulmonary irritation or general anesthetic effects with R-(+)-limonene < or =1,599 ppm and S-(-)-limonene < or =2,421 ppm. R-(+)-limonene did not influence VT below 629 ppm. S-(-)-limonene increased VT above 1,900 ppm. Both enantiomers induced a mild bronchoconstrictive effect above 1,000 ppm.

Formation of strong airway irritants in terpene/ozone mixtures

The American Society for Testing and Materials (ASTM) mouse bioassay, which quantifies airway irritation from reduction in the respiratory rate, was used to find evidence for the formation of highly irritating substances in reactions of ozone with terpenes (common indoor volatile organic compounds (VOCs)). No-observed-effect-levels (NOELs) and concentration-effect relationships were established for ozone, (+)-alpha-pinene and R-(+)-limonene, isoprene, and some of their major reaction products. Reaction mixtures of excess terpene and ozone considerably below their NOEL concentrations resulted in significant upper airway irritation. The reduction of the respiratory rate was from 30% to about 50%, lowest for the alpha-pinene and highest for the isoprene mixture. Chemical analysis of reaction mixtures by conventional methods showed that readily identified stable products and residual reactants at the concentrations found could not account for the observed reductions of the respiratory rate, assuming additivity of the reaction products. The results suggest that, in addition to known irritants (formaldehyde, acrolein, methacrolein, methyl vinylketone), one or more strong airway irritant(s) of unknown structure(s) were formed. Future indoor air quality (IAQ) guidelines for unsaturated VOCs (e.g., terpenes) and their emission from building products may require the consideration of reactions with oxidants, like ozone. Similarly, effects of ozone-emitting equipment should be re-evaluated.

Effects of methacrolein on the respiratory tract in mice

The acute respiratory effects of airborne exposure to methacrolein were studied in a recent refinement of the standard test method with mice (ASTM, 1984. American Society for Testing and Materials, Philadelphia). Irritation of the upper respiratory tract caused a concentration-dependent decrease in the respiratory rate of 2-26 ppm methacrolein. In this range, only a minor airflow limitation occurred in the lower respiratory tract, suggesting that the main effect of methacrolein is sensory irritation. During exposure, the sensory irritation response maintained the same level, i.e. no desensitisation occurred. The concentration 10.4 ppm methacrolein reduced the respiratory rate by 50% (RD50). The extrapolated threshold for the respiratory depressing effect, RD0, was 1.3 ppm. The sensory irritation effect of methacrolein was compared with results from closely related compounds in order to elucidate the mechanism of the interaction between methacrolein and the sensory irritant receptor.

Effects of industrial detergents on the barrier function of human skin

Detergents are involved in the causation of contact dermatitis and in promoting percutaneous absorption of toxic chemicals, but limited information is available to allow an assessment of their relative effects on the skin barrier function. The effect of detergents on skin permeability to water and nickel was examined in an in-vitro model using human skin. Twenty-four of the most widely used detergents were studied. After a two-hour exposure to an aqueous detergent solution, penetration of labeled model compounds was followed for 66 hours. Interindividual variation was substantial, but 12 of the detergents caused statistically significant increases in the penetration of water, nickel, or both. Nonionic detergents were as likely as anionic detergents to have this effect. This study demonstrates that useful information may be obtained by a simple in-vitro method, and that such data may provide a basis for substitution efforts.

Acute airway effects of formaldehyde and ozone in BALB/c mice

1. Concentration and time-effect relationships of formaldehyde and ozone on the airways were investigated in BALB/c mice. The effects were obtained by continuous monitoring of the respiratory rate, tidal volume, expiratory flow rate, time of inspiration, time of expiration, and respiratory patterns. 2. With concentrations up to 4 p.p.m., formaldehyde showed mainly sensory irritation effects of the upper airways that decrease the respiratory rate from a trigeminal reflex. The no-effect level (NOEL) was about 0.3 p.p.m. This value is close to the human NOEL, which is about 0.08 p.p.m. 3. Ozone caused rapid, shallow breathing in BALB/c mice. Later on, the respiratory rate decreased due to another vagal response that indicated an incipient lung oedema. The NOEL in mice was about 1 p.p.m. during 30 min of ozone exposure. No major effect occurs in resting humans at about 0.4 p.p.m. 4. Thus, the upper airway irritant, formaldehyde, and the deep lung irritant, ozone, showed the same types of respiratory effects in humans and in BALB/c mice. Also, the sensitivity was nearly identical. Continuous monitoring of respiratory effects in BALB/c mice, therefore, may be a valuable method for the study of effects of other environmental pollutants, which, however, should be confirmed in further studies.

Absorption and retention of nickel from drinking water in relation to food intake and nickel sensitivity

Two studies were performed to examine the influence of fasting and food intake on the absorption and retention of nickel added to drinking water and to determine if nickel sensitization played any role in this regard. First, eight nonallergic male volunteers fasted overnight before being given nickel in drinking water (12 micrograms Ni/kg) and, at different time intervals, standardized 1400-kJ portions of scrambled eggs. When nickel was ingested in water 30 min or 1 h prior to the meal, peak nickel concentrations in serum occurred 1 h after the water intake, and the peak was 13-fold higher than the one seen 1 h after simultaneous intake of nickel-containing water and scrambled eggs. In the latter case, a smaller, delayed peak occurred 3 h after the meal. Median urinary nickel excretion half-times varied between 19.9 and 26.7 h. Within 3 days, the amount of nickel excreted corresponded to 2.5% of the nickel ingested when it was mixed into the scrambled eggs. Increasing amounts were excreted as the interval between the water and the meal increased, with 25.8% of the administered dose being excreted when the eggs were served 4 h prior to the nickel-containing drinking water. In the second experiment, a stable nickel isotope, 61Ni, was given in drinking water to 20 nickel-sensitized women and 20 age-matched controls, both groups having vesicular hand eczema of the pompholyx type. Nine of 20 nickel allergic eczema patients experienced aggravation of hand eczema after nickel administration, and three also developed a maculopapular exanthema. No exacerbation was seen in the control group. The course of nickel absorption and excretion in the allergic groups did not differ and was similar to the pattern seen in the first study, although the absorption in the women was less. A sex-related difference in gastric emptying rates may play a role. Thus, food intake and gastric emptying are of substantial significance for the bioavailability of nickel from aqueous solutions.

A theoretical approach to the Ferguson principle and its use with non-reactive and reactive airborne chemicals

The Ferguson principle has been widely used in toxicology to separate or indicate possible mechanisms for acute toxic effects of chemicals. However, this principle has never been adequately tested because of the lack of a database containing a sufficient number of both types of chemicals, non-reactive and reactive, that the Ferguson principle purports to separate. Such a database is now available. In this report a theoretical framework for the Ferguson principle is presented, regarding one of the acute toxicological effects of volatile airborne chemicals: sensory irritation. Previously obtained results on series of non-reactive and reactive chemicals are then used to demonstrate that the Ferguson principle can be extended to reactive chemicals by adding chemical reactivity descriptors to the physicochemical descriptors required by the Ferguson principle. This approach can be successful, provided that specific chemical reactivity mechanisms can be identified for the reactive chemicals of concern. The findings suggest that it is possible to replace the empirical Ferguson principle by formal mechanistic equations which will provide a better foundation for the understanding of the mechanisms by which airborne sensory irritants exert their action.

Respiratory effects in mice exposed to airborne emissions from Stachybotrys chartarum and implications for risk assessment

Stachybotrys chartarum, a mycotoxin producing mould found in some damp buildings, was grown in aluminum dishes in closed exposure chambers. The loading factor, 5.12 m2/m3, corresponded to 2.8 times the loading in a normal room with all surfaces covered by mould. Sensory irritation, bronchoconstriction and pulmonary irritation effects were investigated using a sensitive mouse bioassay in which the airway reactions were measured plethysmographically. Little effect was seen from the vapours in agreement with the predicted effects of the low concentrations of volatile organic compounds measured. Even under the influence of an airflow about four times that measured in normal buildings, the concentration of liberated spores and other particles was very low, corresponding to the biological effects observed, and probably reflecting the high water content of the substrate. These results demonstrate that many factors are important for the transport of biologically active mould metabolites from building material to occupants and that no direct relationship may exist between immediate biological effects and surface area covered with mould. Therefore, risk assessments should be based on estimated effects of emitted vapours, effects of liberated particles, e.g. sensitization potentials of the mould spores and effects of the generated metabolites (mycotoxins).

Structure-activity relationships of volatile organic chemicals as sensory irritants

We used a database of 145 volatile organic chemicals for which the sensory irritation potency (RD50) has been reported in mice. Chemicals were first separated into two groups: nonreactive and reactive, using Ferguson's rule. This rule suggests that nonreactive chemicals induce their effect via a physical (p) mechanism (i.e., weak forces or interactions between a chemical and a biological receptor). Therefore, appropriate physicochemical descriptors can be used to estimate their potency. For reactives, a chemical (c) mechanism (i.e., covalent bonding with the receptor) would explain their potency. All chemicals were also separated on the basis of functional groups and subgroups into 24 classifications. Our results indicated that the potency of nonreactive chemicals, regardless of their chemical structure, can be estimated using a variety of physicochemical descriptors. For reactive chemicals, we identified five basic reactivity mechanisms which explained why their potency was higher than that estimated from physicochemical descriptors. We concluded that Ferguson's proposed rule is adequate initially to classify two separate mechanisms of receptor interactions, p vs c. Several physicochemical descriptors can be used to estimate the potency of p chemicals, but chemical reactivity descriptors are needed to estimate the potency for c chemicals. At present, this is the largest database for nonreactive-reactive chemicals in toxicology. Because of the wide variety of c chemicals presented, a semi-quantitative estimate of the potency of new, or not previously evaluated, c chemicals can be arrived at via comparison with those presented and the basic chemical reactivity mechanisms presented.

Sensory irritation mechanisms investigated from model compounds: trifluoroethanol, hexafluoroisopropanol and methyl hexafluoroisopropyl ether

Quantitative structure-activity relationships (QSAR) have suggested the importance of hydrogen bonding in relation to activation of the sensory irritant receptor by nonreactive volatile organic chemicals. To investigate this possibility further, three model compounds with different hydrogen bond acidity, trifluoroethanol, hexafluoroisopropanol and methyl hexafluoroisopropyl ether, were selected for study. The potency of each chemical is obtained from the concentration necessary to reduce respiratory rate in mice by 50% (RD50). The RD50 values obtained were: methyl hexafluoroisopropyl ether (> or = 160,000 ppm), trifluoroethanol (11,400-23,300 ppm), and hexafluoroisopropanol (165 ppm). QSAR showed that trifluoroethanol and methyl hexafluoroisopropyl ether behaved as predicted as nonreactive sensory irritants, whereas hexafluoroisopropanol was much more potent than predicted. The higher than predicted potency of hexafluoroisopropanol could be due to a coupled reaction, involving both strong hydrogen bonding and weak Brönsted acidity. A concerted reaction could thus be more efficient in activation of the receptor. Hydrogen bonding properties and concerted reactions may be important in the activation of the sensory irritant receptor by nonreactive volatile organic chemicals.

Estimating the sensory irritating potency of airborne nonreactive volatile organic chemicals and their mixtures

This article describes the possibility of estimating whether or not a mixture of nonreactive volatile organic chemicals (NRVOC) is likely to elicit complaints of sensory irritation in humans. For this estimation we rely on: a) the sensory irritating potency of individual NRVOC can be estimated from a variety of physicochemical properties of these chemicals, b) at low exposure concentrations, the additivity rule can be applied using the potency of each chemical in a mixture and c) a threshold concentration exists below which no sensory irritation will occur. We used this estimating approach and we compared the results obtained with those obtained experimentally in humans exposed to a well defined mixture. The approach presented can be used to arrive at a decision as to whether or not exposure to a mixture of NRVOC is likely to result in sensory irritation complaints by humans, either in the general indoor air situation or for industrial workers.