Prospective epidemiologic evaluation of laboratory animal allergy among university employees

OBJECTIVES

Evaluation of incidence and risk factors for development of laboratory animal allergy (LAA) among new hires previously unexposed to lab animals.

METHODS

Baseline, 6-month and yearly follow-up, questionnaires, pulmonary functions, and methacholine challenges were collected from 98 never-before occupationally exposed and 90 control laboratory researchers. The two groups were followed between 6 and 36 months.

RESULTS

At baseline, there were no differences in atopy, pulmonary functions, or methacholine reactivity between the two groups. The incidence of work-related asthma was comparable in the two groups, approximately 2.5% at 6 months and 4.5% at 24 months. The rate of decline in FEV1 was statistically significantly greater in the animal-exposed than nonanimal-exposed workers, and animal-exposed smokers' FEV1 declined significantly more rapidly than any other groups'.

CONCLUSION

Despite the low incidence of laboratory-animal allergy and work-related asthma in this group, this study corroborates previously described interaction between smoking and animal exposure.

Field evaluation of endotoxin air sampling assay methods

This study tested the importance of filter media, extraction and assay protocol, and bioaerosol source on the determination of endotoxin under field conditions in swine and poultry confinement buildings. Multiple simultaneous air samples were collected using glass fiber (GF) and polycarbonate (PC) filters, and these were assayed using two methods in two separate laboratories: an endpoint chromogenic Limulus amebocyte lysate (LAL) assay (QCL) performed in water and a kinetic chromogenic LAL assay (KQCL) performed in buffer with resistant-parallel line estimation analysis (KLARE). In addition, two aqueous filter extraction methods were compared in the QCL assay: 120 min extraction at 22 degrees C with vigorous shaking and 30 min extraction at 68 degrees C with gentle rocking. These extraction methods yielded endotoxin activities that were not significantly different and were very highly correlated. Reproducibility of endotoxin determinations from duplicate air sampling filters was very high (Cronbach alpha all > 0.94). When analyzed by the QCL method GF filters yielded significantly higher endotoxin activity than PC filters. QCL and KLARE methods gave similar estimates for endotoxin activity from PC filters; however, GF filters analyzed by the QCL method yielded significantly higher endotoxin activity estimates, suggesting enhancement of the QCL assay or inhibition of the KLARE asay with GF filters. Correlation between QCL-GF and QCL-PC was high (r = 0.98) while that between KLARE-GF and KLARE-PC was moderate (r = 0.68). Analysis of variance demonstrated that assay methodology, filter-type, barn-type, and interactions between assay and filter-type and between assay and barn-type were important factors influencing endotoxin exposure assessment.

CpG motifs in bacterial DNA cause inflammation in the lower respiratory tract

Since unmethylated CpG motifs are more frequent in DNA from bacteria than vertebrates, and the unmethylated CpG motif has recently been reported to have stimulatory effects on lymphocytes, we speculated that bacterial DNA may induce inflammation in the lower respiratory tract through its content of unmethylated CpG motifs. To determine the role of bacterial DNA in lower airway inflammation, we intratracheally instilled prokaryotic and eukaryotic DNA in C3H/HeBFEJ mice and performed whole lung lavage 4 h after the exposure. Heat denatured, single stranded Escherichia coli genomic DNA (0.06 ng endotoxin/microg DNA) was compared to heat denatured, single stranded calf thymus DNA (0.007 endotoxin/microg DNA). 10 microg of bacterial DNA, in comparison to 10 microg of calf thymus DNA, resulted in a fourfold increase in the concentration of cells (P = 0.0002), a fivefold increase in the concentration of neutrophils (P = 0.0002), a 50-fold increase in the concentration of TNF-alpha (P = 0.001), and a fourfold increase in the concentration of both IL-6 (P = 0.0003) and macrophage inflammatory protein-2 (P = 0.0001) in the lavage fluid. Importantly, instillation of 0.60 ng of E. coli LPS resulted in a negligible inflammatory response. To test whether the stimulatory effects of bacterial DNA are due to its unmethylated CpG dinucleotides, we methylated the bacterial DNA and also prepared 20 base pair oligonucleotides with and without CpG motifs. In comparison to instillation of untreated bacterial DNA, methylation of the bacterial DNA resulted in a significant reduction in the concentration of cells and cytokines in the lower respiratory tract. Moreover, oligonucleotides containing embedded unmethylated CpG motifs resulted in inflammation in the lower respiratory tract that was indistinguishable from that observed with untreated bacterial DNA. In contrast, oligonucleotides without the embedded CpG motifs or with embedded but methylated CpG motifs resulted in significantly less inflammation in the lower respiratory tract. The possible relevance of these data to human disease was shown by extracting and analyzing DNA in sputum from patients with cystic fibrosis (CF). Approximately 0.1 to 1% of this sputum DNA was bacterial. Intratracheal instillation of highly purified CF sputum DNA caused acute inflammation similar to that induced by bacterial DNA. These findings suggest that bacterial DNA, and unmethylated CpG motifs in particular, may play an important pathogenic role in inflammatory lung disease.

Laboratory comparison of vacuum, OSHA, and HUD sampling methods for lead in household dust

The goals of this project were to evaluate and compare the efficiency and reproducibility of three methods for sampling lead-containing dust in homes. Lead-containing dust was generated in a 1-m3 chamber and uniformly deposited onto surfaces typically found in the home (painted wood, unpainted wood, varnished wood, linoleum, and carpet). Trials with three levels of lead concentrations were performed for each surface. Replicate, side-by-side, surface samples were collected using the Occupational Safety and Health Administration (OSHA) wipe method, the Department of Housing and Urban Development (HUD) wipe method, and a vacuum-filter method. Samples were digested with nitric acid and analyzed using graphite furnace atomic absorption spectroscopy per National Institute of Occupational Safety and Health Method 7105. Recovery for the HUD method was consistently the highest on most surfaces (linoleum, 89.9 to 108.9%; painted wood, 71.2 to 153.7%; unpainted wood, 25.3 to 76.0%; varnished wood, 8.7 to 165.6%). On carpet the vacuum method had a significantly higher recovery (26.2 to 47.8%). For all sampling methods the percent recovery depended on type of surface and lead concentration. The reproducibility of percent recovery for the HUD (pooled coefficient of variation [CV] = 0.22) and OSHA (pooled CV = 0.27) methods was lower than that of the vacuum method (pooled CV = 0.46), though not statistically significant. Reproducibility for all methods did not vary significantly over surface type or lead concentration. Overall, the HUD method yielded the most accurate measurements, with recoveries closest to 100%. It was also more durable than the OSHA method, where Whatman filters were observed to tear.

Respiratory symptoms and lung function abnormalities among machine operators in automobile production

This cross-sectional study was designed to assess differences in prevalence of respiratory symptoms and lung function between machine operators exposed to semisynthetic or soluble metal-working fluids (MWFs) and unexposed assemblers and to assess exposure-response relationships with MWF type, total aerosol, endotoxin, culturable bacteria and fungi. We evaluated 183 machine operators and 66 assemblers from one large automobile transmission plant using questionnaires, spirometry data, and cross-shift assessment of both lung function and respiratory symptoms. We found that airborne exposures to total aerosol, endotoxin, culturable bacteria and fungi were higher in machine operations than in the assembly area. There was a correlation between bulk and airborne culturable bacteria, but not between bulk and airborne culturable fungi. Machine operators had significantly more usual cough, usual phlegm, work-related chest tightness and post-shift symptoms of chest tightness, throat irritation, and cough compared with assemblers. We found exposure-response relationships between respiratory symptoms and total aerosol, as well as culturable fungi and bacteria. Associations with endotoxin were not strong or consistent, possibly because airborne levels were generally low. Cross-shift lung function decrements did not differ between machine operators and assemblers and there were no associations with MWF or specific exposures. The finding of respiratory symptoms at low levels of exposure in this study suggests the need to re-assess total aerosol thresholds. Associations between airborne fungal exposures and respiratory symptoms need further study to characterize sources of exposure other than MWF in machining operations.

Application of flow cytometry and fluorescent in situ hybridization for assessment of exposures to airborne bacteria

Current limitations in the methodology for enumeration and identification of airborne bacteria compromise the precision and accuracy of bioaerosol exposure assessment. In this study, flow cytometry and fluorescent in situ hybridization (FISH) were evaluated for the assessment of exposures to airborne bacteria. Laboratory-generated two-component bioaerosols in exposures chambers and complex native bioaerosols in swine barns were sampled with two types of liquid impingers (all-glass impinger-30 and May 3-stage impinger). Aliquots of collection media were processed and enumerated by a standard culture technique, microscopy, or flow cytometry after nucleic acid staining with 4',6-diamidino-2-phenylindole (DAPI) and identified taxonomically by FISH. DAPI-labeled impinger samples yielded comparable estimates of bioaerosol concentrations when enumerated by microscopy or flow cytometry. The standard culture method underestimated bioaerosol concentrations by 2 orders of magnitude when compared to microscopy or flow cytometry. In the FISH method, aliquots of collection media were incubated with a probe universally complementary to eubacteria, a probe specific for several Pseudomonas species, and a probe complementary to eubacteria for detection of nonspecific binding. With these probes, FISH allowed quantitative identification of Pseudomonas aeruginosa and Escherichia coli bioaerosols in the exposure chamber without measurable nonspecific binding. Impinger samples from the swine barn demonstrated the efficacy of the FISH method for the identification of eubacteria in a complex organic dust. This work demonstrates the potential of emerging molecular techniques to complement traditional methods of bioaerosol exposure assessment.

The kinetics of grain dust-induced inflammation of the lower respiratory tract

To characterize the kinetics of grain dust-induced airflow obstruction and inflammation in the lower respiratory tract, we performed serial spirometry and bronchoalveolar lavage (BAL) in human subjects and whole-lung lavage in mice following a single inhalation exposure to comparable dosages of corn dust extract (CDE). Following inhalation of CDE, our human study subjects developed significant airflow obstruction 10 min postexposure which persisted for 48 h. Human subjects and mice had similar acute and persistent changes in lavage cellularity after exposure to CDE. A profound increase in the concentration of lavage neutrophils was present in the initial postexposure lavage in both human subjects and mice. This increase persisted for 96 h in human subjects and 48 h in mice. Small but significant increases in lavage macrophage concentration were present 48 h postexposure in human subjects and at 96 h postexposure in mice. Inhalation of CDE resulted in a significant increase in the concentration of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the lavage fluid of both human subjects and mice. Similarly, significant increases in lavage concentrations of IL-8 in humans and macrophage inflammatory protein-2 (MIP-2) in mice occurred after inhalation of CDE. The lavage concentration of all measured proinflammatory cytokines returned to baseline levels by 168 h in humans and 96 h in mice. These findings suggest that a single inhalation challenge of CDE results in airflow obstruction and lower respiratory tract inflammation that may last for several days. These physiologic and inflammatory responses appear to be self-limited with no evidence of persistent injury 1 wk after the inhalation challenge. Moreover, the inflammatory response in the lower respiratory tract after inhalation of grain dust is similar in human subjects and mice, suggesting that the mouse may be an appropriate model for further investigation of grain dust-induced inflammation.

Pulmonary effects of machining fluids in guinea pigs and mice

Acute pulmonary effects of inhalation exposure to (unused) neat and in-use metalworking fluids (MWF) were studied to evaluate the potency of characterized MWF in terms of their effects on breathing and lung inflammation. Inhalation exposure of guinea pigs caused dose-dependent changes in respiratory rate and volume that were used to quantify potency. In-use MWF was consistently more toxic than the corresponding neat MWF. Significant predictors of respiratory responses were whether MWF was neat or in-use (p = 0.0001), exposure concentration (p = 0.022), MWF formulation (p = 0.031), and the particular in-use MWF tested (p = 0.032). Inhalation exposures to MWF biocides resulted in dose-dependent sensory irritation responses. Guinea pig studies revealed significant inflammation resulting from MWF exposure marked by change in bronchoalveolar lavage (BAL) fluid from 3% neutrophils (controls) to 60-79% (MWF-exposed) and 25-fold increase in total BAL cells. The in-use MWF ranged in endotoxin concentration from 280 to 1.7 x 10(5) endotoxin units (EU)/mL. To investigate the role of endotoxin, studies were carried out in mice sensitive (SEN) and resistant (RES) to endotoxin. SEN mice revealed a dose-dependent 10,000-fold increase in BAL neutrophils and a 100-fold increased concentration of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) following inhalation exposure to in-use MWF. This inflammatory response was not observed with exposure to neat MWF or with sham exposure. RES mice demonstrated virtually no response to the inhaled MWF for total cells, neutrophils, IL-6, or TNF-alpha. Removal of microorganisms by filtration of the in-use MWF did not change the responses observed in either strain. These studies demonstrate that lung inflammation may be an important outcome from exposure to in-use MWF and that endotoxin is a toxicant of importance.

The utility of preliminary surveys to detect the cause of acute metalworking fluid hazards

This paper describes preliminary studies undertaken to optimize a later epidemiologic study, the aim of which was to identify a causative agent of adverse respiratory effects and dermatitis among production machinists. Two methods were used to rate coolant system hazards. The results of a voluntary plantwide questionnaire with an 18% participation rate showed that both dermatologic and respiratory symptoms were higher among machine operators than among maintenance or assembly workers, that symptoms were not more prevalent early in the week, and that dermatitis may be associated with smoking status; however, the questionnaire was not helpful in rating individual coolant system hazards. The hazard ratings provided by an in-plant expert panel were strongly associated with particular synthetic coolant containing an ethoxylated phenol; however, the resulting design for a later epidemiologic study could not be implemented due to changes in coolants used at the plant.

Dermatitis among automobile production machine operators exposed to metal-working fluids

This cross-sectional study was designed to assess differences in prevalence of contact dermatitis between machine operators exposed to metal-working fluids (MWFs) and unexposed assemblers, and to assess potential risk factors for contact dermatitis among these machine operators. In their work, machine operators were exposed to either semisynthetic or soluble oil MWFs. We evaluated 158 machine operators and 51 assemblers from one large automobile transmission plant using questionnaires, dermatologist examination of the skin, and dermal dosimetry to measure wetness and metal exposures. We found that machine operators had more combined (definite plus possible) dermatitis (27.2% vs. 13.7%, chi(2) = 3.9, p = 0.05, 1 df) compared with assemblers. Among machine operators, risk factors significantly associated with (combined) dermatitis were subjective assessment of wetness of the work, exposure to semisynthetic as opposed to soluble oil MWF, current cigarette smoking, and increasing worker age. These risk factors suggested preventive and control measures including control of wet work, surveillance program including early self-report of dermatitis, consideration of replacement of semisynthetic with soluble oil MWFs, and strictly limiting smoking among machine operators exposed to MWFs.

The role of atopy in grain dust-induced airway disease

To determine whether atopy influences the physiologic or inflammatory response to grain dust, we compared spirometric measures of airflow and bronchoalveolar lavage (BAL) measures of lower respiratory tract inflammation between demographically similar nonatopic (n = 10) and atopic (n = 10) study subjects after each of two inhalation exposures: Hanks' balanced salt solution (HBSS) and corn dust extract (CDE; 0.4 microgram of endotoxin/kg body weight). Subjects were healthy nonsmokers with similar baseline pulmonary function, without bronchial hyperreactivity, and had not participated in agriculture. Atopic subjects had two or more positive skin responses to 10 common environmental allergens. Both groups developed significant airflow obstruction and lower airway inflammation after CDE inhalation. Importantly, the magnitude of the post-CDE exposure airflow decrements, BAL cellularity, and BAL concentration of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, and IL-8 did not significantly differ between atopics and nonatopics. The concentrations of histamine and eosinophils in the BAL fluid were unaffected by CDE inhalation and did not significantly differ between atopics and nonatopics. Atopic status does not appear to be a significant determinant of airflow obstruction or lower airway inflammation following CDE inhalation. Our findings suggest that atopy may play, at most, a minor role in the development of grain dust-induced airway disease.

Grain dust and endotoxin inhalation challenges produce similar inflammatory responses in normal subjects

STUDY OBJECTIVE

To compare the physiologic and inflammatory response following inhalation of corn dust extract (CDE) and lipopolysaccharide (LPS) solutions in normal subjects.

DESIGN

Randomized, double-blind crossover design.

PARTICIPANTS

Fourteen healthy, nonatopic, nonasthmatic, never-smoking volunteers.

INTERVENTIONS

On separate visits, subjects underwent a series of four inhalation challenges to LPS or CDE, each containing either a high (6 micrograms/mL) or low (0.9 microgram/mL) endotoxin concentration, and administered at equal Xolumes.

RESULTS

Chest tightness, cough, dyspnea, and sputum production were experienced following both LPS and CDE exposures and with similar frequency at both high and low endotoxin concentrations. LPS and CDE inhalations caused acute declines in FEV1, and the changes in FEV1 from baseline following exposure to both inhalants were not significantly different at both high and low endotoxin concentrations. Following exposure to the high-endotoxin LPS and CDE, no consistent differences in total cell and cytokine (tumor necrosis factor-alpha [TNF-alpha], interleukin-1 beta [IL-1 beta], IL-6, IL-8) concentrations were seen between exposures, although the neutrophil concentration was greater following the LPS exposure (p = 0.01). BAL cellularity and cytokine concentrations following the low-endotoxin LPS and CDE exposure revealed no differences, except for IL-1 beta, which was greater following LPS exposure (p = 0.05). The high-endotoxin LPS and CDE exposures resulted in greater increases in BAL neutrophils and cytokines in comparison to its respective low-endotoxin exposure.

CONCLUSIONS

At exposure levels of endotoxin, LPS and CDE result in similar symptoms, changes in airflow, and increases in BAL inflammatory cells and mediators. Moreover, the physiologic and inflammatory response to LPS and CDE appears to be related to the exposure level of endotoxin.

Role of endotoxin in grain dust-induced lung inflammation in mice

To investigate the role of endotoxin in grain dust-induced airway inflammation, we reduced the endotoxin activity from extracts of corn dust (CDE), using three distinct methods, and determined the effect of endotoxin activity on the in vitro and in vivo inflammatory response to CDE. Escherichia coli lipopolysaccharide solution (LPS) and CDE solution were separated into > 100-kDa and < 100-kDa fractions by ultracentrifugation. Endotoxin activity was predominantly present in the > 100-kDa fractions of the LPS and CDE solutions. Charged-membrane filtration of the > 100-kDa fractions of LPS and CDE resulted in the reduction of endotoxin activity by 99.9 and 80%, respectively. Treatment of the > 100-kDa fractions of LPS and CDE with polymyxin B-coated beads reduced the endotoxin activity by 96 and 89%, respectively. The untreated > 100-kDa fractions of LPS and CDE caused significantly greater (P < 0.01) release of tumor necrosis factor-alpha (TNF-alpha) from THP-1 cells in vitro compared with its respective < 100-kDa fraction or either of the treated (charged filter or polymyxin B) > 100-kDa fractions. Similarly, mice exposed to either of the untreated > 100-kDa fractions of LPS or CDE by inhalation developed significantly greater (P < 0.01) concentrations of lavage neutrophils and TNF-alpha in the lavage fluid compared with mice exposed to the respective < 100-kDa fraction or either of the treated > 100-kDa fractions. These results indicate that endotoxin is primarily responsible for the in vitro and in vivo inflammatory response to CDE.

Nasal lavage cellularity, grain dust, and airflow obstruction

To evaluate the clinical utility of nasal lavage (NL), we performed post-work shift NL on 172 grain workers and 78 postal worker control subjects. The grain worker group included a higher percentage of current smokers (25.7% vs 16.7%) and a lower percentage of former smokers (21.15% vs 35.9%) compared with the postal workers. The control subjects included more female workers and were slightly older than the grain workers. Compared with the postal workers, the grain workers were exposed to significantly greater concentrations of total dust (0.1 +/- 0.0 vs 6.8 +/- 1.4 mg/m3; mean +/- SEM) and total endotoxin (4.3 +/- 0.8 vs 2,372.4 +/- 653.8 endotoxin units/m3). NL from gain workers showed a higher concentration of total cells (55,000 +/- 14,000 vs 25,000 +/- 5,000 cells per milliliter; p=0.03), a higher concentration of squamous epithelial cells (17,029.0 +/- 4,177 .0 vs 7,103.7 +/- 1,479.8 cells per milliliter; p=0.03), and a higher concentration of neutrophils (40,058.0 +/- 12,803.2 vs 17,891.0 +/- 3,822.3 cells per milliliter; p=0.10) compared with postal workers. Importantly, these differences in NL cellularity between grain workers and postal workers were observed within the three strata of smokers. To further assess the importance of total cells, squamous epithelial cells, and neutrophils in the NL fluid of grain workers, we investigated the relationship between these cell concentrations and (1) measures of dust and endotoxin exposure during the work shift. (2) spirometric measures of airflow obtained immediately before the NL, and (3) work-related respiratory symptoms. The concentration of total cells, the concentration of squamous epithelial cells, or the concentration of neutrophils in the NL was not associated with ambient levels of dust or endotoxin, with baseline or cross-shift changes in lung function, or with work-related respiratory symptoms. These findings suggest that increased NL cellularity may be seen in workers exposed to high dust levels. However, the NL cellularity does not appear to be associated with ambient concentrations of dusts or endotoxins, with signs of airflow obstruction, or with work-related respiratory symptoms.

Epidemiologic assessment of laboratory animal allergy among university employees

The prevalence of, and risk factors for, laboratory animal allergy (LAA) among university employees were evaluated in a cross-sectional university-based study. A stratified random sample was drawn based on current or no laboratory animal exposure and smoking status. Participants received a modified ATS questionnaire; spirometry; methacholine challenge; and intradermal allergen skin tests. One hundred three currently animal-exposed and 113 never-occupationally-exposed employees participated. Controlling for smoking, currently exposed workers were significantly more likely than controls to describe work-related cough, odds ratio (O.R.) = 6.87; wheeze, O.R. = 12.96; and chest tightness, O.R. = 2.89. Skin test reactivity to non-animal antigens was associated in a dose-response fashion with both upper and lower respiratory symptoms, O.R. = 1.45 and 1.65, respectively, for each additional positive skin test. Exposed workers were significantly more likely than controls to react to methacholine at either 10 or 25 mg/ml, while controlling for smoking status, prior allergy, or asthma. Multiple logistic regression analysis revealed history of hay fever, family history of allergy, non-animal skin test positivity, animal bites, age, and smoking status to each be associated with work-related respiratory symptoms. These data suggest that atopy and smoking status are risk factors for LAA symptoms. Smoking was associated with work-related respiratory symptoms among animal-exposed workers, but not with skin test positivity. It is therefore recommended that periodic screening evaluations be performed on laboratory animal workers and that workers who are atopic, are smokers, or are symptomatic be placed in low exposure settings. These data further, support the need for efficient exhaust ventilation, personal protective clothing and, among high risk workers, the use of efficient respiratory protection.

The role of endotoxin in grain dust-induced lung disease

To identify the role of endotoxin in grain dust-induced lung disease, we conducted a population-based, cross-sectional investigation among grain handlers and postal workers. The study subjects were selected by randomly sampling all grain facilities and post offices within 100 miles of Iowa City. Our study population consisted of 410 grain workers and 201 postal workers. Grain workers were found to be exposed to higher concentrations of airborne dust (p = 0.0001) and endotoxin (p = 0.0001) when compared with postal workers. Grain workers had a significantly higher prevalence of work-related (cough, phlegm, wheezing, chest tightness, and dyspnea) and chronic (usual cough or phlegm production) respiratory symptoms than postal workers. Moreover, after controlling for age, gender, and cigarette smoking status, work-related respiratory symptoms were strongly associated with the concentration of endotoxin in the bioaerosol in the work setting. The concentration of total dust in the bioaerosol was marginally related to these respiratory problems. After controlling for age, gender, and cigarette smoking status, grain workers were found to have reduced spirometric measures of airflow (FEV1, FEV1/FVC, and FEF25-75) and enhanced airway reactivity to inhaled histamine when compared with postal workers. Although the total dust concentration in the work environment appeared to have little effect on these measures of airflow obstruction, higher concentrations of endotoxin in the bioaerosol were associated with diminished measures of airflow and enhanced bronchial reactivity. Our results indicate that the concentration of endotoxin in the bioaerosol may be particularly important in the development of grain dust-induced lung disease.

Endotoxin responsiveness and grain dust-induced inflammation in the lower respiratory tract

To identify the role of endotoxin responsiveness in grain dust-induced airway disease, we used two models of extotoxin hyporesponsiveness to perform inhalation exposure studies in mice. In the first model, we investigated whether genetic resistance to endotoxin would alter the inflammatory response to inhaled grain dust by comparing the inflammatory response in the lower respiratory tract of endotoxin-sensitive and -resistant male mice after inhalation of pyrogen-free saline, corn dust extract (CDE), sterile CDE (SCDE), or lipopolysaccharide (LPS). Endotoxin-sensitive and -resistant mice were exposed for 4 h to nebulized solutions of LPS, SCDE, or CDE. Another group of endotoxin-sensitive and -resistant mice was sham exposed for 4 h to nebulized sterile saline. Dose-response relationships for endotoxin were explored for LPS, SCDE, and CDE. Bronchoalveolar lavage (BAL) 5 h after the start of exposure demonstrated a higher concentration of total cells, neutrophils (PMNs), and tumor necrosis factor-alpha (TNF-alpha) in BAL fluid after inhalation of CDE, SCDE, or LPS in endotoxin-sensitive than in endotoxin-resistant mice. Whereas endotoxin-sensitive mice demonstrated a dose-response relationship between the endotoxin concentration in each of the solutions and the concentration of cells, PMNs, and TNF-alpha in BAL fluid, concentrations of TNF-alpha were significantly higher only in BAL fluid of endotoxin-resistant mice exposed to higher concentrations of SCDE or CDE. In the second model, we investigated whether acquired endotoxin tolerance would alter the inflammatory response to SCDE.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioaerosol sampling in field studies: can samples be express mailed?

Bioaerosol sampling for viable microorganisms was conducted in 25 dairy barns in summer and in winter to examine the relationship of sample storage and shipping in determining bioaerosol concentrations separately for yeasts, molds, mesophilic bacteria, and thermophilic organisms. The study also compared the performance of three sampling methods--(1) all-glass impinger (AGI) used with peptone solution in both seasons and (2) betaine solution in winter; and (3) the nuclepore filtration and elution (NFE) method, using air filtration with subsequent elution and culturing--which were studied in a pairwise fashion with duplicate, simultaneous, side-by-side sampling. For each sample, one duplicate was analyzed within two hours in a laboratory less than 50 km from the sampling site, while the other was express-mailed to the authors' laboratory. Concentrations of all microorganisms measured by the AGI peptone method were unaffected by mailing in winter, but mesophilic bacteria increased in summer. AGI betaine samples were unchanged except for increased concentrations of molds after mailing in winter. Yeasts and mesophilic bacteria significantly decreased after mailing of NFE samples. Pairwise comparison of the sampling methods in winter yielded no significant differences in airborne concentrations for the yeasts, mesophilic bacteria, and thermophilic bacteria. Both AGI betaine and NFE methods had significantly greater concentrations of molds than AGI peptone. In summer, concentrations of yeasts and mesophilic bacteria were significantly greater with AGI peptone, as were molds with the NFE method.(ABSTRACT TRUNCATED AT 250 WORDS)

Grain dust-induced airflow obstruction and inflammation of the lower respiratory tract

To investigate the relationship between the physiologic and biologic effects of grain dust inhalation, we exposed 15 nonsmoking, nonasthmatic, nonatopic male grain handlers to buffered saline and aqueous corn dust extract by inhalation challenge in a crossover study. The inhalation challenges to buffered saline and corn dust extract were separated by at least 14 d. Compared with buffered saline, inhalation of corn dust extract resulted in significant airflow obstruction, which was observed within 30 min of exposure and persisted for 5 h. Inhalation of corn dust extract resulted in an acute inflammatory response characterized by higher concentrations of neutrophils (p = 0.001), IL-1 beta (p = 0.001), IL-1RA (p = 0.001), IL-6 (p = 0.001), IL-8 (p = 0.001), and TNF-alpha (p = 0.04) in bronchoalveolar lavage (BAL) fluid. mRNA levels specific for IL-1 beta, IL-1RA, IL-6, and IL-8 from cells present in the BAL fluid were significantly greater after challenge with corn dust extract than after challenge with buffered saline. Importantly, no significant differences were observed in the concentration of lymphocytes or eosinophils in the BAL fluid following inhalation of corn dust extract, and the concentrations of histamine and 15-HETE were similar in BAL fluid after the two challenges. The maximal percentage decrease in FEV1 was significantly associated with the absolute neutrophil concentration in the BAL fluid (p = 0.001), as well as the concentration of TNF-alpha (p = 0.03), IL-1 beta (p = 0.005), IL-1RA (p = 0.001), IL-6 (p = 0.001), and IL-8 (p = 0.001) in the BAL fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Agents in organic dust: criteria for a causal relationship

Identification of agents of disease causation in organic dust is complicated by the fact that multiple agents may be involved, and these agents may act in a synergistic or additive fashion and cause a number of conditions resulting from chronic toxic or inflammatory effects. A new systematic approach to evaluating available data for evidence of disease-causing agents in organic dust is proposed. It combines, in a matrix fashion, principles of Koch's postulates, River's postulates, principles of epidemiologic determinants, and weight of evidence theory. By applying these principles in a systematic fashion, the strength of the scientific evidence for a specific agent can objectively be evaluated.

Experimental grain dust atmospheres generated by wet and dry aerosolization techniques

Properties of grain dust aerosols generated using wet and dry techniques were studied. Relative to the dry aerosol generation, the wet generation technique yielded a smaller particle size distribution (MMAED of 1.5 microns vs. 15.5 microns) but also reduced the viability of microorganisms. Analysis of dust mass and endotoxin activity on cascade impactor stages demonstrated equivalent partitioning of the airborne endotoxin with the dust mass for aerosols produced by either generation method. Comparison of laboratory-generated atmospheres to field sampling indicated a greater proportion of respirable microorganisms in soybean handling facilities than were generated using the dry aerosol system. Limitations of both aerosol generation systems were found that may affect the validity of inhalation toxicology studies in which these bioaerosols are artificially created.

The effects of inhalation of grain dust extract and endotoxin on upper and lower airways

To characterize the short-term effects of grain dusts on pulmonary function, mucosal inflammation, and systemic responses, four women and three men inhaled nebulized corn and soybean dust extracts, endotoxin diluted with Hanks' balanced salt solution (HBSS), and HBSS. Subjects were volunteers recruited via newspaper advertisement and were required to be healthy, nonasthmatic, nonatopic never-smokers. The mean age was 26.9 years (range, 19 to 36 years). Using a randomized, double-blind, crossover design, each subject was challenged with each of the 4 substances with at least 10 days between challenges. Serial spirometry, peripheral blood leukocyte and differential cell counts, and 24-h postchallenge nasal lavages were performed. Extracts were produced by mixing 3 g of the corn or soybean dust with 30 ml HBSS followed by shaking for 60 min, centrifugation, then filter sterilization. The endotoxin solution was produced by mixing lyophilized Escherichia coli endotoxin (serotype 0111:B4) with HBSS to attain a final concentration of 7 mg/L, which was the same as the concentration of endotoxin in both grain dust solutions. The pH of all solutions and unmixed HBSS was adjusted to 5.8, which was the native pH of the soybean dust extract. Subjects were challenged with 0.08 ml/kg of each substance, resulting in a range of endotoxin doses of 30 to 60 micrograms, similar to that which a worker might inhale over the course of one workshift. The lowest mean percentage baseline FEV1 (+/- SD) after inhalation challenge was 99.2 +/- 2.1 for HBSS, and it was significantly lower for endotoxin (90.1 +/- 8.5, p = 0.03), corn dust extract (93.1 +/- 4.3, p = 0.02), and soybean dust extract (96.2 +/- 3.7, p = 0.03). In addition, a peripheral blood leukocytosis developed after exposure to all three endotoxin-containing solutions (p < 0.05), yet a lower peripheral blood lymphocyte count was found only after inhalation of corn dust extract (p = 0.02). Interestingly, this was associated with a higher nasal lavage lymphocyte count after inhalation of corn dust extract (p = 0.03). Neither the decrease in peripheral blood lymphocytes nor the increase in nasal lymphocytes were found after inhalation of soybean dust extract or endotoxin. Our results indicate that extracts of grain dusts have physiologic effects similar to endotoxin. However, in spite of the same endotoxin levels, the effects of corn dust extract appear to have different biologic activity than either soybean dust extract or endotoxin.

Sump additives as a source of bioaerosols in a school building

An investigation was launched following complaints of poor air quality and building-related illness in a public elementary school. Occlusion of air intakes put the building under negative pressure and caused vents from a below-ground sump to become air intakes. Outside air drawn through the sump pit traveled into the adjacent main air handling unit and was disseminated throughout the building. Sump additives introduced in an attempt to counteract foul odors contained spores of Bacillus species, which appeared as bioaerosols throughout the school. Viable microbial sampling identified B subtilis, B cereus, and B licheniformis in the sump room and classrooms at levels as high as 760 colony forming units/m3 (CFU/m3). Concentrations of CO2 in classrooms were 1250 ppm, indicating inadequate makeup air. Remediation was accomplished by opening the air intakes, isolating the sump room from the air handling system, venting the sump to the outside, and flushing the sump with fresh water on a regular basis.

Comparison of bioaerosol sampling methods in barns housing swine

The air in livestock buildings contains bioaerosol levels that are sufficiently high to cause adverse health effects in animals and workers. These bioaerosols are complex mixtures of live and dead microorganisms and their products as well as other aeroallergens. The effectiveness of sampling methods used for quantifying the very high concentrations of microorganisms in these environments has not been well studied. To facilitate an accurate assessment of respiratory hazards from viable organisms in agricultural environments, three bioaerosol sampling methods were investigated: the Andersen microbial sampler method (AMS), the all-glass impinger method (AGI), and the Nuclepore filtration-elution method (NFE). These methods were studied in a parallel fashion in 24 swine confinement buildings. Measurements were taken in two seasons with three types of culture media in duplicate to assess total bacteria, gram-negative enteric bacteria, and total fungi. Methods were analyzed for the proportion of samples yielding data within the limits of detection, intraclass reliability, and correlation between methods. For sampling viable bacteria, the AMS had a poor data yield because of overloading and demonstrated weak correlation with the AGI. Conversely, the AGI and NFE gave sufficient numbers of valid data points (90%), yielded high intraclass reliabilities (alpha greater than or equal to 0.92), and were highly correlated with each other (r = 0.86). The AGI and the NFE were suitable methods for assessing bacteria in this environment, but the AMS was not. The AMS was the only method that consistently recovered enteric bacteria (73% data yield). For sampling fungi, the AGI and AMS both yielded sufficient data and all three methods demonstrated high intraclass reliability.(ABSTRACT TRUNCATED AT 250 WORDS)