Setting Occupational Exposure Limits for Chemical Allergens--Understanding the Challenges

Chemical allergens represent a significant health burden in the workplace. Exposures to such chemicals can cause the onset of a diverse group of adverse health effects triggered by immune-mediated responses. Common responses associated with workplace exposures to low molecular weight (LMW) chemical allergens range from allergic contact dermatitis to life-threatening cases of asthma. Establishing occupational exposure limits (OELs) for chemical allergens presents numerous difficulties for occupational hygiene professionals. Few OELs have been developed for LMW allergens because of the unique biological mechanisms that govern the immune-mediated responses. The purpose of this article is to explore the primary challenges confronting the establishment of OELs for LMW allergens. Specific topics include: (1) understanding the biology of LMW chemical allergies as it applies to setting OELs; (2) selecting the appropriate immune-mediated response (i.e., sensitization versus elicitation); (3) characterizing the dose (concentration)-response relationship of immune-mediated responses; (4) determining the impact of temporal exposure patterns (i.e., cumulative versus acute exposures); and (5) understanding the role of individual susceptibility and exposure route. Additional information is presented on the importance of using alternative exposure recommendations and risk management practices, including medical surveillance, to aid in protecting workers from exposures to LMW allergens when OELs cannot be established.

Identification of phenolic dermal sensitizers in a wound closure tape

A latex-allergic patient presented with a severe local reaction to a non-latex wound closure bandage following surgery. Extracts of the bandage were analyzed by gas chromatograph-electron impact-mass spectrometry (GC EI-MS) in the total ion monitoring mode. Components were identified by their ion mass fingerprint and elution time as a corresponding standard from the GC column. The chemicals identified were 4,4'-thiobis-(6-tert-butyl-m-cresol) (TBBC), 6-tert-Butyl-m-cresol (BC), 2,4-di-tert-butylphenol (BP) and erucamide (EA). Sensitization potential of these chemicals was evaluated using two quantitative structure-activity relationship (QSAR) programs. The phenol 2,6-di-tert-butyl-4-(hydroxymethyl)phenol (BHP) was also included in the test series. It was initially thought to be present in the bandage but detectable levels could not be confirmed. The potential for TBBC to induce a sensitization response was predicted by both Derek for Windows and TOPKAT 6.2. The potential for BC and BP to induce a sensitization response was predicted by Derek for Windows, but not TOPKAT. BHP and EA were not predicted to be sensitizers by either QSAR program. Local lymph node assay (LLNA) analysis of the chemicals identified TBBC, BP, and BC as potential sensitizers with EC3 values between 0.2 and 4.5%. None of the animals exhibited body weight loss or skin irritation at the concentrations tested. In agreement with the toxicological modeling, BHP did not induce a sensitization response in the LLNA. Following a positive LLNA response, TBBC, BP, and BC were further characterized by phenotypic analysis of the draining lymph nodes. A positive LLNA result coupled with a lack of increase in B220(+)IgE(+) cell and serum IgE characterize these chemicals as Type IV sensitizers. These studies used a multidisciplinary approach combining clinical observation, GC-EI-MS for chemical identification, QSAR modeling of chemicals prior to animal testing, and the LLNA for determination of the sensitization potential of chemicals in a manufactured product.

Occupational sensitization to soy allergens in workers at a processing facility

BACKGROUND

Exposure to soy antigens has been associated with asthma in community outbreaks and in some workplaces. Recently, 135 soy flake processing workers (SPWs) in a Tennessee facility were evaluated for immune reactivity to soy. Allergic sensitization to soy was common and was five times more prevalent than in health care worker controls (HCWs) with no known soy exposure.

OBJECTIVE

To characterize sensitization to soy allergens in SPWs.

METHODS

Sera that were positive to soy ImmunoCAP (n=27) were tested in IgE immunoblots. Wild-type (WT) and transgenic (TG) antigens were sequenced using nanoscale Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry (nanoUPLC MS/MS). IgE reactivity towards 5-enolpyruvylshikimate-3-phosphate synthase (CP4-EPSP), a protein found in TG soy, was additionally investigated. De-identified sera from 50 HCWs were used as a control.

RESULTS

Immunoblotting of WT and TG soy flake extracts revealed IgE against multiple soy antigens with reactivity towards 48, 54, and 62 kDa bands being the most common. The prominent proteins that bound SPW IgE were identified by nanoUPLC MS/MS analysis to be the high molecular weight soybean storage proteins, β-conglycinin (Gly m 5), and Glycinin (Gly m 6). No specific IgE reactivity could be detected to lower molecular weight soy allergens, Gly m 1 and Gly m 2, in soybean hull (SH) extracts. IgE reactivity was comparable between WT and TG extracts; however, IgE antibodies to CP4-EPSP could not be detected.

CONCLUSIONS AND CLINICAL RELEVANCE

SPWs with specific IgE to soy reacted most commonly with higher molecular weight soybean storage proteins compared with the lower molecular weight SH allergens identified in community asthma studies. IgE reactivity was comparable between WT and TG soy extracts, while no IgE reactivity to CP4-EPSP was observed. High molecular weight soybean storage allergens, Gly m 5 and Gly m 6, may be respiratory sensitizers in occupational exposed SPWs.

Changes in asthma-like responses after extended removal from exposure to trimellitic anhydride in the Brown Norway rat model

BACKGROUND

Organic acid anhydride-induced occupational asthma is considered to be IgE-mediated. Airway and skin exposure are the two main routes of sensitization in the work place. Recently we developed an allergic asthmatic Brown Norway rat model sensitized by dermal exposure to trimellitic anhydride (TMA) using an occlusion patch application.

OBJECTIVES

The objectives of this study were (1) to develop a model of non-occluded dermal exposure leading to allergic sensitization and (2) to examine the effect of extended removal from exposure on persistence of both specific IgE and TMA aerosol-induced airway responses in this model.

METHODS

TMA powder (4 or 40 mg) was applied, unoccluded, to the skin of rats for 4 h, once/week for 4 weeks. Rats were given a 10-min aerosol challenge to 40 mg/m(3) TMA 2 weeks after the last dermal exposure (day 35). Another group was challenged on day 35 and again 18-24 months later. Respiratory enhanced pause (Penh), pulmonary histopathology and inflammation and specific IgE titres were measured.

RESULTS

Rats produced dose-dependent specific IgE titres after exposure and developed early-phase (EAR) and late-phase airway responses (LAR) after airway challenge to TMA aerosol as well as airway eosinophilic inflammation. Specific airway responses were still manifested after a second TMA airway challenge given 18-24 months following the initial airway challenge. While persistent, airway inflammation, specific IgE and EAR were significantly attenuated following the second TMA challenge. LAR remained robust at 18-24 months and was not significantly different from the response on day 35.

CONCLUSIONS

These results demonstrate the persistence of chemical sensitization and further suggest that IgE is not essential for LAR.

Respiratory inflammatory responses among occupants of a water-damaged office building

The National Institute for Occupational Safety and Health (NIOSH) received a request for evaluation of a water-damaged office building which housed approximately 1300 employees. Workers reported respiratory conditions that they perceived to be building related. We hypothesized that these symptoms were associated with airways inflammation. To test this hypothesis, we assessed airways inflammation in employees using exhaled breath condensate (EBC) and the fraction of exhaled nitric oxide (FENO). In September 2001, a health questionnaire was offered to all employees. Based on this questionnaire, NIOSH invited 356 symptomatic and asymptomatic employees to participate in a medical survey. In June 2002, these employees were offered questionnaire, spirometry, methacholine challenge test, allergen skin prick testing, EBC and FENO. FENO or EBC were completed by 239 participants. As smoking is highly related to the measurements that we used in this study, we included only the 207 current non-smokers in the analyses. EBC interleukin-8 (IL-8) levels, but not nitrite, were significantly higher among workers with respiratory symptoms and in the physician-diagnosed asthmatic group. Of the analyses assessed, EBC IL-8 showed the most significant relationship with a number of symptoms and physician-diagnosed asthma.

PRACTICAL IMPLICATIONS

Implementation of exhaled breath condensate and exhaled nitric oxide in indoor air quality problems.

Survey of sulfur-containing rubber accelerator levels in latex and nitrile exam gloves

2-Mercaptobenzothiazole and zinc dialkyldithiocarbamates are commonly used sulfur-containing rubber vulcanization accelerators known to cause allergic contact dermatitis. Exposure to these agents occurs through clothing such as undergarments and shoes, latex medical devices and latex and nitrile gloves. A simple, inexpensive screening method for total sulfur accelerator and a high performance liquid chromatographic speciation method were developed in the present study. These methods were applied to screen and quantify the sulfur accelerator content from 38 brands of 'off-the-shelf' latex and nitrile gloves obtained from commercial vendors. It was found that accelerator levels ranged from not detectable to 7.35 mg/g in the gloves analysed. Brands were found to contain single and multiple accelerator species within the glove. Powdered gloves had significantly higher accelerator levels than powder-free gloves from the same manufacturer; however, these chemical accelerators do not preferentially partition to the powder. The present analytical methodology is suitable for both manufacturing quality validation purposes, as well as for accelerator allergy research.

Determination of 3-amino-5-mercapto-1,2,4-triazole in serum

A high performance liquid chromatography (HPLC) method using fluorescence detection to determine 3-amino-5-mercapto-1,2,4-triazole (AMT) levels in serum has been developed. Sample preparation involved treatment with tributylphosphine (TBP) to reduce disulfides formed during storage, precipitation of proteins with acetonitrile (ACN), and precolumn derivatization using the thiol reactive fluorescent probe monobromobimane (MBB). The conjugate (AMT-MBB) was resolved by gradient elution from a C(18) reversed-phase column. The assay method was linear over a concentration range of 0.78-50 microg/ml and had a limit of detection (LOD) of 0.05 microg/ml AMT (10 microl injection). This method provides a sensitive and specific tool for the determination of AMT in serum and may have potential industrial hygiene application.

Determination of Zinc Dialkyldithiocarbamates in Latex Condoms

A simple high-performance liquid chromatographic (HPLC) assay is developed for measuring zinc dialkyldithiocarbamate (DTC) levels in latex condoms. After extraction of 14 different brands of latex condoms in acetonitrile, aliquots of the extracts are subjected to a preliminary screening assay by treatment with cobalt chloride and measurement of UV absorption at 320 nm, which results in the identification of 6 DTC-containing samples. Prior to analysis by HPLC, zinc dimethyldithiocarbamate (ZDMC) or zinc diethyldithiocarbamate (ZDEC) is added to the extracts in order to block transmetalation reactions with the analytes of interest. A reversed-phase C(18) column, with gradient elution and UV detection at 260 nm, is used to measure the zinc DTCs. The limits of detection for ZDEC and zinc dibutyldithiocarbamate (ZDBC) are 5 and 10 micro g/mL. Levels of ZDBC and ZDEC range from not detectable to 3.31 and 1.79 mg/condom, respectively. Total protein and latex allergenic protein levels are determined and range from 98 to 776 and 0.01 to 14.04 micro g/unit, respectively, but are not related to the level of ZDBC or ZDEC. This methodology provides both screening and specific tools for the determination of unstable zinc DTC complexes in latex products.

Effects of paving asphalt fume exposure on genotoxic and mutagenic activities in the rat lung

Asphalt fumes are complex mixtures of aerosols and vapors containing various organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Previously, we have demonstrated that inhalation exposure of rats to asphalt fumes resulted in dose-dependent induction of CYP1A1 with concomitant down-regulation of CYP2B1 and increased phase II enzyme quinone reductase activity in the rat lung. In the present study, the potential genotoxic effects of asphalt fume exposure due to altered lung microsomal enzymes were studied. Rats were exposed to air or asphalt fume generated under road paving conditions at various concentrations and sacrificed the next day. Alveolar macrophages (AM) were obtained by bronchoalveolar lavage and examined for DNA damage using the comet assay. To evaluate the systemic genotoxic effect of asphalt fume, micronuclei formation in bone marrow polychromatic erythrocytes (PCEs) was monitored. Lung S9 from various exposure groups was isolated from tissue homogenates and characterized for metabolic activity in activating 2-aminoanthracene (2-AA) and benzo[a]pyrene (BaP) mutagenicity using the Ames test with Salmonella typhimurium YG1024 and YG1029. This study showed that the paving asphalt fumes significantly induced DNA damage in AM, as revealed by DNA migration in the comet assay, in a dose-dependent manner, whereas the micronuclei formation in bone marrow PCEs was not detected even at a very high exposure level (1733 mg h/m3). The conversion of 2-AA to mutagens in the Ames test required lung S9-mediated metabolic activation in a dose-dependent manner. In comparison to the controls, lung S9 from rats exposed to asphalt fume at a total exposure level of 479+/-33 mg h/m3 did not significantly enhance 2-AA mutagenicity with either S. typhimurium YG1024 or YG1029. At a higher total asphalt fume exposure level (1150+/-63 mg h/m3), S9 significantly increased the mutagenicity of 2-AA as compared to the control. However, S9 from asphalt fume-exposed rats did not significantly activate the mutagenicity of BaP in the Ames test. These results show that asphalt fume exposure, which significantly altered both phases I and II metabolic enzymes in lung microsomes, is genotoxic to AM and enhances the metabolic activation of certain mutagens through altered S9 content.

Alteration of pulmonary cytochrome p-450 system: effects of asphalt fume condensate exposure

Exposure to asphalt fumes is a health concern due to the presence of polycyclic aromatic compounds (PACs) in asphalt. Bioactivation of many PACs requires metabolism by the cytochrome P-450 (P-450) system. The objective of this study was to evaluate the effects of exposure of rats to asphalt fume condensate (AFC), collected at the top of a paving asphalt storage tank, on the pulmonary microsomal P-450 system and to determine the genotoxic effects of such exposure. Male Sprague-Dawley rats were intratracheally instilled with saline or with 0.45, 2.22, or 8.88 mg/kg AFC for 3 consecutive days and sacrificed the following day. Lung microsomes were isolated by differential centrifugation of lung homogenates. Microsomal protein level, NADPH cytochrome c reductase activity, and the activities and protein levels of cytochrome P-450 isozymes CYP1A1 and CYP2B1 were monitored to assess the effects of AFC exposure on pulmonary P-450. The activities of CYP2B1 and CYP1A1 were determined by monitoring xenobiotic metabolism of 7-pentoxyresorufin and 7-ethoxyresorufin, respectively. CYP2B1 and CYP1A1 levels were determined by immunochemical analysis. Micronucleus (MN) formation in bone-marrow polychromatic erythrocytes (PCEs) was determined to assess the genotoxic effects of AFC exposure. The results showed that exposure of rats to AFC did not significantly affect total cytochrome P-450 content or cytochrome c reductase activity in the lung. CYP2B1 levels and enzyme activity were not significantly affected by AFC exposure. In contrast, CYP1A1 levels and activity were significantly increased in microsomes isolated from AFC-exposed lungs. Increased MN formation was observed only in high-dose AFC-exposed bone marrow PCEs. These results demonstrate that AFC exposure induced CYP1A1 activity and increased the enzyme levels of CYP1A1 in lung microsomes, suggesting that AFC exposure may alter metabolism of PACs by the cytochrome P-450 system in the lung. Alteration of cytochrome P-450 metabolism of PACs may contribute to the AFC-induced genotoxic effects demonstrated as MN formation.

Dose-response and time course of specific IgE and IgG after single and repeated topical skin exposure to dry trimellitic anhydride powder in a Brown Norway rat model

BACKGROUND

Trimellitic anhydride (TMA)-induced occupational asthma is thought to be associated with its ability to acylate proteins and to induce production of TMA-specific immunoglobulin (Ig)E. Though the respiratory tract is considered to be a major exposure route leading to airway sensitization, the potential role of dermal exposure producing asthmatic sensitization is not known. The present study examines the ability of dry TMA powder to sensitize Brown Norway rats when applied, topically, to the skin.

METHODS

A patch of hair was carefully clipped with scissors on the rat's back. Dry TMA powder (0.3, 1.25, 5 and 20 mg) was administered on days 0, 7, 14 and 21, and the area occluded with surgical tape overnight after each application. Residual powder recovered from the occluded skin was analyzed by proton nuclear magnetic resonance and was still predominantly TMA. Circulating anti-TMA IgE and IgG were measured by ELISA.

RESULTS

TMA elicited dose-dependent production of specific IgE and IgG. Specific antibodies were detectable 2 weeks after the first TMA exposure and peaked between 3 and 4 weeks.

CONCLUSION

The data suggest that topical skin exposure to dry TMA powder can induce allergic/immunological sensitization as demonstrated by the production of specific antibodies.

Differentiation of the mechanism of micronuclei induced by cysteine and glutathione conjugates of methylenedi-p-phenyl diisocyanate from that of 4,4'-methylenedianiline

Methylenedi-p-phenyl diisocyanate (MDI) is widely used in the production of polyurethane products. Diisocyanates are reactive compounds, MDI can react under physiological conditions with various functional groups found on biological molecules resulting in conjugate formation or undergo non-enzymatic hydrolysis to form 4,4'-methylenedianiline (MDA). We have previously reported that addition of MDI directly to Chinese hamster lung fibroblasts (V79) cultures did not induce micronuclei (MN), but MDA, and the glutathione and cysteine conjugates of MDI (BisGS-MDI and BisCYS-MDI), induced a concentration-dependent increase in the frequency of MN. The conventional MN assay does not discriminate between MN produced by acentric chromosome fragments from those arising due to whole lagging chromosomes that were not incorporated into daughter nuclei at the time of cell division. The mechanism of MN induction from these potential MDI metabolites/reaction products was explored in the present study using immunofluorescent staining of kinetochore in MN of cytokinesis-blocked V79 cells. This assay discerns the presence of centromere within the MN to distinguish the MN containing centric chromosomes from those containing acentric fragments. Eighty five percent of MDA-induced MN were negative with respect to anti-kinetochore antibody binding (KC(-)). This is consistent with an interaction between MDA and DNA resulting in chromosome breakage. However, BisGS-MDI and BisCYS-MDI induced a higher percentage of MN that were positively stained by the anti-kinetochore antibody (KC(+)). These results suggest that the mechanism of MN formation induced by BisGS-MDI and BisCYS-MDI is mediated through disruption and/or by affecting the function of the mitotic spindle. This mechanism is distinctly different from the mechanism of MN induction by MDA.

Characterization of asphalt fume composition under simulated road paving conditions by GC/MS and microflow LC/quadrupole time-of-flight MS

A highly sensitive, selective, and reliable analytical method has been developed and validated for characterization of asphalt fume generated under simulated road paving conditions. A dynamic asphalt fume generation system was modified to provide consistent test atmospheres at simulated asphalt road paving conditions. In the process of fume generation, asphalt was initially preheated in an oven to 170 degrees C, pumped to a large kettle, which maintained the asphalt temperature between 150 and 170 degrees C, and then transferred to the generator. The fume was conducted from the generator to an exposure chamber through a heated transfer line. Characterization of the asphalt fume test atmospheres included the following: (1) determination of the consistency of the asphalt aerosol composition within the generation system; (2) quantification of total organic matter of the asphalt fume by electron impact ionization of isotope dilution gas chromatography/ mass spectrometry); and (3) identification of individual priority polycyclic aromatic hydrocarbons (PAHs) in asphalt fume by selected ion monitoring. With the developed method, asphalt fumes could be characterized into three fractions: (1) filter collection of a large molecular size fraction over a range of mass-to-charge (m/z) ratios of 173-309; (2) XAD-2 trapping of a medium molecular size fraction over a range of m/z ratios of 121-197; and (3) charcoal trapping of a small molecular size fraction that contained mainly the volatile vapor fraction over a range of m/z ratios of 57-141. Total organic matter of the asphalt fume was quantified over the 5 exposure days. Sixteen specific priority PAHs were monitored and identified. These PAHs were determined at trace levels on the filter fraction. A novel approach, which utilizes collision-induced dissociation of fragmentation pathway leading to a characteristic fragmentation pattern by coupling microflow liquid chromatography to atmospheric pressure chemical ionization of quadrupole time-of-flight mass spectrometry, was used to further clarify the trace amount of key components present in simulated road paving asphalt fumes. These results demonstrate that asphalt fume composition could be characterized and specific priority PAHs could be identified by this method. The major advantages of this method are its highly sensitivity, selectivity, and reliability for chemical hazard characterization in a complex mixture. This method is suitable for support toxicity studies using simulated occupational exposure to asphalt fumes.

Induction of micronuclei following exposure to methylene di-phenyl diisocyanate: potential genotoxic metabolites

Methylene di-phenyl diisocyanate (MDI) is used to make polyurethane products. The predominant occupational disease attributed to diisocyanates, including MDI, is asthma; however, the potential for genotoxicity has also been of concern. Diisocyanates are very reactive compounds that can undergo nonenzymatic hydrolysis to form methylenedianiline (MDA), or react under physiological conditions with primary amines to form ureas and/or with thiols to form labile thiol acid esters. MDA is a carcinogen in animals and a suspected carcinogen in humans. Brown Norway rats (BNR) were exposed to either 7 or 113 mg/m(3) MDI aerosol for 1 h/week x3 weeks and sacrificed 1 week later. Micronuclei (MN) formation was assessed from bone marrow polychromatic erythrocytes (PCE). A dose-dependent increase in the frequency of micronucleated polychromatic erythrocytes (MN-PCEs) was noted. In vitro exposure of Chinese hamster lung fibroblasts (V79) to MDA or MDI-thiol conjugates, but not to MDI, significantly increased the frequency of MN. MDI-thiol conjugate-exposed cell cultures did not have detectable levels of MDA. A significant increase in the number of V79 cells in metaphase, as well as the number of cells with precipitants within both the cytoplasm and nuclei, were noted in MDI-glutathione-exposed cultures. The results of this study indicate that MDI aerosol exposure can cause MN formation through either the hydrolysis of MDI to MDA or possibly the formation of thiol conjugates.

Asthma-like symptoms in wood product plant workers exposed to methylene diphenyl diisocyanate

BACKGROUND

Diisocyanates, a group of highly reactive chemicals, have frequently been associated with occupational asthma. We evaluated respiratory health in workers at a new wood products manufacturing plant that uses methylene diphenyl diisocyanate (MDI), and was designed and operated with a goal of minimizing worker exposures.

METHODS

Health surveys using standardized respiratory questionnaires were done prior to the initial use of diisocyanates in the plant, and semiannually thereafter for a period of 2 years. Other testing included occupational and work practice histories, serial peak flow measurements, spirometry, methacholine challenge, and measurement of specific IgE antibodies to MDI-albumin conjugate.

RESULTS

Of 214 plant employees who participated in at least one health survey, a follow-up survey was also available from 178 employees (83%). New-onset asthma-like symptoms (NAS) were reported by 15 of 56 workers (27%) in areas with the highest potential for exposures to liquid MDI monomer and prepolymer, vs 0 of 43 workers in the lowest potential exposure areas (p = 0.001). In the areas with high potential exposure, NAS developed in 47% of workers who had noted MDI skin staining, vs 19% without skin stains (p = 0.07). Working around and cleaning up liquid MDI represented a significant risk for asthma-like symptoms in both current smokers and nonsmokers; work with finished wood products did not. Asthma-like symptoms were associated with variable airflow limitation (odds ratio [OR], 5.0; confidence interval [CI], 1.4 to 18.7) and specific IgE to MDI-albumin (OR, 3.2; CI, 1.1 to 9.0), but not with skin prick tests to common aeroallergens (OR, 1.1; CI, 0.5 to 2.7).

CONCLUSIONS

During the first 2 years of operation, in a plant designed and operated to control exposure to diisocyanates, the development of asthma-like symptoms was reported in a relatively high proportion of the employees who worked with liquid MDI. To prevent asthma symptoms among workers, careful control of respiratory tract exposures associated with liquid MDI is important, especially during cleanup activities. Strict limitation of skin contact with diisocyanates may also be necessary.

Ovalbumin aeroallergen exposure-response in Brown Norway rats

A major route of exposure to allergens is through the respiratory tract. Comparatively few animal studies have used aerosolized high-molecular-weight allergens for sensitization, and in these studies, proper characterization of the aeroallergen exposure was usually missing. The purpose of this study was to profile the exposure-response relationship in Brown Norway rats (BNR) to well-characterized ovalbumin (OVA) aerosols. Rats were exposed 30 min/wk x 6 wk to respirable OVA aerosols from <1 mg/m(3) to 64 mg/m(3) air. Ovalbumin-specific circulating immunoglobulin (Ig)E, IgG, and IgA were measured throughout the study period. Rats were sacrificed 1 day after the last exposure. Pulmonary tissue was processed for histopathological and histochemical analysis. Tracheas were isolated, perfused, and assessed for in vitro responsiveness to methacholine. Serum concentrations of OVA-specific antibodies increased with both exposure concentration and number of exposures. The number of BNR with measurable titers also increased with both dose and time. Pulmonary inflammatory changes were noted only in BNR exposed to higher OVA concentrations (15 and 64 mg/m(3) air). Increased tracheal reactivity to methacholine was not found in any of the sensitized BNR. In summary, sustained aeroallergen concentration-dependent changes in specific antibody responses and pulmonary inflammation have been demonstrated.

Molecular markers of acute upper airway inflammation in workers exposed to fuel-oil ash

Biomarkers in nasal lavage (NL) fluid may be useful in determining the presence and severity of upper airway inflammation. We studied 18 boilermakers overhauling a large, oil-fired boiler and 11 utility workers who served as controls for 6 wk. NL was performed before (NL1), during (NL2), and after (NL3) the overhaul. We measured nasal fluid levels of interleukins 6 (IL-6) and 8 (IL-8), eosinophilic cationic protein (ECP), and myeloperoxidase (MPO) as markers of response to fuel-oil ash exposure. In boilermakers, MPO was elevated during boiler work versus preboiler work (mean = 33.8 versus 22.7 ng/ml, p < 0.05), and at the 2-wk postexposure lavage (NL3) it had declined to 24.2 ng/ml (p = 0.08). Mean IL-8 levels increased in boilermakers between NL1 and NL2 (mean = 83.8 versus 134.8 pg/ml, p < 0.05), then decreased at NL3 (mean = 134.8 versus 89.0 pg/ml, p < 0.05). Nasal fluid vanadium increased in boilermakers between NL1 and NL2 (median < 1.0 versus 4.7 ppb, respectively, p < 0.05), then decreased at NL3 (median, 4.7 versus < 1.0 ppb, respectively, p < 0. 05). Levels of IL-6 and ECP did not change significantly during the study. Utility workers showed no significant change in any marker during the study period. Particulate matter < 10 micro(m) (PM10) levels were higher for boilermakers than for utility workers before boiler work (geometric mean (GM) = 0.40 versus 0.10 mg/m3, p < 0.05). This difference was more significant during boiler work (GM = 0.47 versus 0.13 mg/m3, p < 0.001). Ozone levels were low during the study. These data suggest that exposure to fuel-oil ash results in acute upper airway inflammation, potentially mediated by increased IL-8 levels and the recruitment and activation of polymorphonuclear leukocytes. These changes were associated with significantly increased PM10 levels and concentrations of upper airway vanadium.

Organic dust exposures from work in dairy barns

Environmental surveys were conducted in 85 barns, predominantly dairy, in central Wisconsin to characterize exposures to organic dusts and dust constituents from routine barn work. Environmental analytes included airborne dusts (total, inhalable inlet, and respirable), particle size distributions, endotoxins, total spore and bacteria counts, viable bacteria and fungi, histamine, cow urine antigen, mite antigen, ammonia, carbon dioxide, and hydrogen sulfide. The geometric mean (GM) concentration of airborne dusts include area total, 0.74 mg/m3; personal inhalable inlet, 1.78 mg/m3, and area respirable, 0.07 mg/m3. Viable bacteria and fungi, spores, endotoxins, histamine, cow urine antigen, and mite antigen were quantifiable constituents of these organic dusts and potential respiratory exposure hazards from routine dairy barn work. Endotoxin concentrations from the inhalable inlet samples ranged from 25.4 endotoxin units per cubic meter of air (EU/m3) to 34,800 EU/m3. The GM endotoxin concentration from these samples, 647 EU/m3, exceeds estimated threshold exposure levels for respiratory health effects. Ammonia was a common irritant quantified in most dairy barns. There were significant correlations between the concentrations of organic dusts and certain dust constituents, although in most instances these correlations were not strong. These sampling results demonstrate the complex nature of organic dusts and provide quantitative description of the exposures to toxic and immunogenic dust constituents during routine barn work.

Adjuvant effect of respiratory irritation on pulmonary allergic sensitization: time and site dependency

It has been suggested that airway irritation, by acting as an adjuvant, as well as producing damage, may be an important factor related to asthma. The present study examined the window of time following acute upper and lower airway irritant exposure to determine the period of increased risk of immunological sensitization. Brown Norway rats were exposed to 87 ppm NO2 or 1000 ppm NH3 for 1 hr. A 30-min ovalbumin (OVA) exposure of 18.14 microg/liter air was given at various times based upon the time course of irritant associated inflammatory response (either immediately prior to or 1 or 7 days after the irritant exposure). OVA-only, NO2-only or NH3-only controls, and saline controls were also studied. Weekly booster exposures of OVA (or saline) were given. Circulating OVA-specific IgE, IgA, and IgG levels were quantified periodically during the 6 weeks of the study. Bronchoalveolar lavage (BAL) was also performed to examine the inflammatory response to allergic and irritant challenge. Significant increases in OVA-specific IgE, IgG, and IgA antibody titers were seen in rats given the sensitizing OVA exposure within 1 day of the NO2, but not NH3 exposures. Enhancement of cellular infiltrate in BAL was noted in groups given the sensitizing OVA exposure within 1 day of the NO2 or NH3. It is concluded that the inflammatory and immunological response to antigen exposure can be modified by the site of respiratory tract irritation and the relative times of irritant and antigen exposure.

Acute lung injury induced by a commercial leather conditioner

Following a formulation change, a leather conditioner was involved in a 1992 nationwide outbreak of respiratory illness. We investigated the composition and toxicity of the conditioner produced before (previous product) and after (new product) the disease outbreak. The new product induced tachypnea, pulmonary edema, pulmonary hemorrhage, and sporadic deaths in exposed guinea pigs and rats. Ultrastructurally, these changes were associate with direct pulmonary cytotoxicity characterized by necrosis of alveolar type I cells and alveolar septal interstitial edema. Chemical analyses suggested major alterations in the fluorohydrocarbon constituents in the new formulation of the leather conditioner. While these alterations could not be specifically identified, they appeared to include changes from fluoralkanes to fluoroalkenes, fluorophenyl, and/or fluoroalcohol compounds. Changes in solvent composition were consistent with traces of 2-butoxyethanol and isomers of dipropylene glycol methyl ether, and additional C10-C12 alkanes. In this study, we demonstrated the toxicity of the new product in laboratory animals. Some of the altered constituents of the new product have been identified and are potential candidates for additional investigations to identify specific etiologic agents.

Respiratory complications of gastroesophageal reflux disease

There is a relationship between gastroesophageal reflux disease and certain respiratory symptoms and findings. Among these are cough, laryngitis, and wheezing dyspnea. The pathophysiology of these conditions can vary from actual aspiration of gastric content to esophageal mucosal inflammation with the respiratory symptoms induced by a vagally mediated reflex mechanism.

A sensitive new bioassay for tumor necrosis factor

Tumor necrosis factor is an important cytokine involved in inflammation and assay of this cytokine in biological fluids may be important in the understanding of several disease processes. This report describes an improved TNF bioassay employing a newly isolated subclone of the cell line NCTC-clone 929 as well as a novel fluorescence indicator system for detecting viability of the target cells. The limit of detection for the TNF hypersensitive cell line with this fluorescence viability assay was 68 +/- 2.5 fg/ml, which is approximately 3 x more sensitive than the parental clone and approximately 10 x more sensitive than that reported by Branch et al. (1991) using the neutral red indicator system. The hypersensitivity of the clone gradually declined over a 45-day period and at regular intervals new cells were cultivated from frozen stocks. Two different serum sources, bovine fetal serum and horse serum, and four different serum concentrations (5, 10, 15, 20%) were evaluated to optimize sensitivity. No difference was found between serum sources but sensitivity was significantly reduced if < 15% serum was used.

Measurement of environmental formylmethionyl-peptides

Formylmethionyl-peptides are naturally occurring, biologically active ligands produced by bacteria. They produce a variety of biological effects including neutrophil chemotaxis, cellular degranulation, oxygen-free radical production, and smooth muscle contraction. Our studies have demonstrated that oxidized and reduced forms of formylmethionyl-leucyl-phenylalanine (fMLP) can be detected in bulk environmental organic dust samples. Organic dust fMLP content may not reflect total formylmethionyl-peptide content and pathological sequelae. Attempts to develop a total formylmethionyl-peptide assay that would reflect its pathological potential have thus far been unsuccessful. Information has been derived concerning the biology of formylmethionyl-peptides from these studies. Chromatographic, radioenzymatic, and radioreceptor-ligand binding studies were performed. High-performance liquid chromatography (HPLC) analysis of synthetic and environmental fMLP demonstrated that fMLP is labile, forming three oxidation products. HPLC is limited by inadequate sensitivity for air sample analysis and the probability of the presence of multiple formylmethionyl-peptides. Deformylases were isolated from Escherichia coli, but their usefulness in a competitive assay to detect formylmethionyl-peptides was limited by specificity differences from that for biological receptors. Receptor binding studies were conducted in an attempt to replace the deformylase with a biological receptor. The receptor binding patterns noted were consistent with the existence of three distinct formylmethionyl-peptide receptor subsets in neutrophils and alveolar macrophages. The plurality of fMLP receptor subtypes interfered with formylmethionyl-peptide measurement in a competitive assay. Formylmethionyl-peptides may contribute to organic dust-induced disease, but better techniques for the assessment of exposure to these agents are needed to properly assess their health impact.

Histamine and endotoxin contamination of hay and respirable hay dust

Three distinct samples collected from a barn in which an outbreak of respiratory problems occurred were examined for possible etiologic agents. No causal relationship could be established from the results of this study; however histamine concentrations as high as 0.5 ng/mg for bulk hay (in the absence of measurable creatinine levels) along with 6138.3 endotoxin units/mg of hay were present in the samples. Both endotoxin and histamine could be recovered from respirable hay dust. The authenticity of the histamine found in the hay was evaluated with high-performance liquid chromatography and radioimmunoassay. Histamine release caused by hay extracts was evaluated with the use of leukocytes from the farmer and a referent. Histamine is known to modulate the immune system, but the role of occupational or environmental exposure to histamine in respiratory disease is unknown.

Observations of the use of o-phthalaldehyde condensation for the measurement of histamine

The in vitro study of mast cell degranulation utilises the measurement of histamine as a quantitative marker of this process. Histamine is most commonly assayed, following organic extraction, by condensing it with o-phthalaldehyde (OPT) and thereby obtaining a highly fluorescent adduct. A number of variables that might affect the performance of this assay, including assay conditions, stability and purity, were evaluated during the course of developing this assay for use in our laboratory. We observed the stability of OPT-histamine and found it to be very stable at 0 and 25 degrees C, following acidification. Derivatisation conditions and the purity of the leukocyte histamine extract were also assessed, and indicated that derivatisation at low temperatures slows down decay, providing a greater over-all fluorescence intensity. Extraction procedures are necessary, prior to condensation with OPT, to eliminate both positive and negative interfering substances from leukocyte preparations.

High-performance liquid chromatographic method for the evaluation of possible interferences in basophil-histamine release measurements

Basophil activation studies commonly rely on the measurement of histamine following extraction and condensation to o-phthalaldehyde (OPT) as a quantitative measurement of degranulation. Specificity has long been recognized as a problem with this method. We have described a new high-performance liquid chromatographic method that allows for both a qualitative and a quantitative check of the purity of the OPT-histamine adduct. This method was sensitive (limit of detection = 2.55 pmol) and linear over a wide range (5 to 1000 ng/ml).

Pharmacologic manipulation of the murine pulmonary biochemical response to NO2

The possible sources of biochemical changes in the lung, including changes in activities of lactate dehydrogenase (LDH), beta-glucuronidase (beta-GLU), choline kinase (CHK), and protease inhibitor (PI), as well as protein content, were evaluated following exposure to NO2. Hydroxyurea-induced granulocytopenia attenuated the LDH and beta-GLU responses (46% and 61%, respectively) following acute, but not subacute, exposure to NO2. Increases in PI activity and pulmonary protein content following exposure to NO2 were not altered by inhibition of protein synthesis by cycloheximide. The observed increase in PI activity appears to result from an activation process, whereas a major source of increased pulmonary protein content following exposure appears to occur from leakage into the lung. The response of the lung to irritant insult is thus dynamic, and the contribution from various sources to the biochemical makeup of the lung following irritant insult may depend on the phase of the pulmonary response.

Neutrophil derived interference in the fluorometric determination of histamine

Zymogen-stimulated neutrophils release many pre- and non-preformed factors including proteolytic enzymes, oxygen free radicals and arachidonic acid metabolites. Measurement of the histamine concentration of a supernatant fluid commonly employs an organic extraction procedure followed by condensation to o-phthalaldehyde. Diamine oxidase digestion studies and high-performance liquid chromatographic analysis suggest that a factor(s) derived from zymogen-stimulated neutrophils can produce a positive interference in the fluorometric determination of histamine.

Phase-dependent response of the lung to NO2 irritant insult

The biochemical and histopathological response of the lung following acute and repeated (subacute) exposure to nitrogen oxide (NO2) was examined. Activities of lactate dehydrogenase, beta-glucuronidase, choline kinase, and protease inhibitor were measured in murine pulmonary tissue immediately and two days following exposure. Nonenzymatic parameters, pulmonary protein content, and wet lung weight were also monitored. Immediately following acute exposure to NO2, only the nonenzymatic parameters were elevated. By two days following acute exposure, following subacute exposure; however, the nonenzymatic parameters were attenuated with respect to the enzymatic activities. The lung exhibits a dynamic response following damage by oxidants such as NO2. This response is divided into three distinct phases (exudative, proliferative, and tolerant), which can be characterized both biochemically and histopathologically.

Ex vivo removal of serum IgG in a patient with colon carcinoma: some biochemical, immunological and histological observations

Plasma of a patient with metastatic colon carcinoma was perfused over Formalin and heat-killed S. aureus, in an extracorporeal filtration apparatus, in order to nonspecifically remove IgG and its complexes. Twenty ex vivo absorption procedures were done, over a five-month period, with a minimum of discomfort to the patient. Extracorporeal perfusion of plasma on S. aureus effectively reduced the levels of IgG and immune complexes in the perfused plasma. The nonspecific removal of IgG resulted in 1) slight biochemical alterations in the serum, 2) a transient reduction in the serum blocking activity and appearance of complement-dependent serum cytotoxicity, 3) an increase in the serum IgM levels, 4) a transient increase in the Ig surface-bearing lymphocytes and a decrease in "E" rosetting lymphocytes in the first 24-48 hours postperfusion, particularly during the early treatments, 5) an improvement in general condition of the patient and decrease in tumor size, and 6) histological changes in the tumor consistent with tumor destruction. The potential problems and clinical applications of procedures involving ex vivo specific or nonspecific immunoabsorbents are discussed.