Measurement of endotoxins in bioaerosols at workplace: a critical review of literature and a standardization issue

Occupational exposure to endotoxins and small cell lung cancer: a systematic review with meta-analysis

The relationship of occupational exposure to endotoxins with different histologic subtypes of lung cancer has not been established. Our objective was to conduct a systematic review with meta-analysis to assess the effect of exposure to endotoxins on the development of small cell lung cancer (SCLC). A bibliographic search was conducted using MEDLINE, Embase, CENTRAL, and Web of Science databases until December 2022, including all cohort and/or case-control studies that examined occupational exposure to endotoxins and SCLC. Risk of bias was assessed using the U.S. Office of Health Assessment and Translation tool. A random effects model was applied, publication bias were assessed, and a sensitivity analysis was conducted. Four papers were selected for meta-analysis purposes. A total of 144 incident cases of SCLC and 897 population or hospital controls were included. Occupational exposure to endotoxins was considered for textile/leather industry and agricultural sector workers exposed to endotoxins originating from wool, cotton, or leather dust. Except for one study, all investigations were classified as having a low probability of risk of biases. The results of the meta-analysis were not statistically significant (pooled OR: 0.86; 95% CI:0.69-1.08). In addition, neither between-study heterogeneity (I2=0%;p=0.92) nor publication bias was observed (p=0.49). The results of the sensitivity analysis, after including five studies that assessed the risk of SCLC among textile industry and crop/livestock farm workers (not specifically exposed to endotoxins), showed a negative statistically non-significant association and low between-study heterogeneity (pooled OR: 0.90; 95% CI:0.79-1.02; I2=22%;p=0.23). Subjects exposed to occupational exposure to endotoxins seem to exhibit a negative association with the development of SCLC, although the results are not conclusive.

Assessment of waste workers occupational risk to microbial agents and cytotoxic effects of mixed contaminants present in the air of waste truck cabin and ventilation filters

Workers in the waste-processing industry are potentially exposed to high concentrations of biological contaminants, leading to respiratory and digestive problems and skin irritations. However, few data on the exposure of waste collection truck (WCT) drivers are available. The goal was to document the microbial risk of the waste collection truck (WCT) workers while in the vehicle cab. Long-period sampling using the truck air filters (CAF) and short time ambient air sampling in the cab were used. The potential release of microbial particles from CAFs was also investigated since it could contribute to the microbial load of the cabin air. A combination of analytical methods also helped assess the complex mixture of the biological agents. Aspergillus sections Fumigati and Flavi, E. coli, Enterobacter spp. and Legionella spp. were detected in the CAF of trucks collecting three types of waste. The highest levels of bacteria and fungi were found in the CAF from organic WCT. The highest endotoxin concentrations in CAF were 300 EU/cm2. Most of the CAF showed cytotoxic effects on both lung cells and hepatocytes. Only one mycotoxin was detected in a CAF. The maximal concentrations in the ambient WCT air varied according to the type of waste collected. The highest proportion (84%) of the air samples without cytotoxic effects on the lungs cells was for the recyclable material WCTs. The results revealed the potential microbial risk to workers from a complex mixture of bio-contaminants in the cabs of vehicles collecting all types of waste. The sustained cytotoxic effect indicates the potential adverse health-related impact of mixed contaminants (biological and non-biological) for the workers. Overall, this study highlights the benefits of using complementary sampling strategy and combined analytical methods for a the assessment of the microbial risk in work environments and the need to implement protective measures for the workers.Implications: Exposure to microbial agents is a well-known occupational hazard in the waste management sector. No previous study had evaluated the cytotoxicity of ambient air and ventilation filters to document worker exposure to a combination of contaminants during waste collection. This research confirms the usefulness of ventilation filters for long-term characterization of exposure to infectious agents, azole-resistant fungi, coliform bacteria and mycotoxin. Overall, this study highlights the importance of using several sampling and analysis methods for a comprehensive assessment of microbial risk in work environments, as well as the need to implement appropriate protective measures for collection workers.

An Assessment of Airborne Bacteria and Fungi in the Female Dormitory Environment: Level, Impact Factors and Dose Rate

In this study, the levels of airborne bacteria and fungi were tested in a female dormitory room; the effects of heating, relative humidity and number of occupants on indoor microorganisms were analyzed and the dose rate of exposure to microbes was assessed. The bacterial and fungal concentrations in the room ranged from 100 to several thousand CFU/m³, and the highest counts were observed in the morning (930 ± 1681 CFU/m³). Staphylococcus spp. and Micrococcus spp. were found in the dormitory. When the heating was on, the total bacterial and fungal counts were lower than when there was no heating. Moreover, statistically significant differences were observed for bacterial concentrations during the morning periods between the times when there was no heating and the times when there was heating. The number of occupants had an obvious positive effect on the total bacterial counts. Moreover, RH had no correlation with the airborne fungi in the dormitory, statistically. Furthermore, the highest dose rate from exposure to bacteria and fungi was observed during sleeping hours. The dose rate from exposure to airborne microorganisms in the dormitory was associated with the activity level in the room. These results helped to elucidate the threat of bioaerosols to the health of female occupants and provide guidance for protective measures.

Bacterial lipopolysaccharide is associated with stroke

We aimed to determine if plasma levels of bacterial lipopolysaccharide (LPS) and lipoteichoic acid (LTA) are associated with different causes of stroke and correlate with C-reactive protein (CRP), LPS-binding protein (LBP), and the NIH stroke scale (NIHSS). Ischemic stroke (cardioembolic (CE), large artery atherosclerosis (LAA), small vessel occlusion (SVO)), intracerebral hemorrhage (ICH), transient ischemic attack (TIA) and control subjects were compared (n = 205). Plasma LPS, LTA, CRP, and LBP levels were quantified by ELISA. LPS and CRP levels were elevated in ischemic strokes (CE, LAA, SVO) and ICH compared to controls. LBP levels were elevated in ischemic strokes (CE, LAA) and ICH. LTA levels were increased in SVO stroke compared to TIA but not controls. LPS levels correlated with CRP and LBP levels in stroke and TIA. LPS, LBP and CRP levels positively correlated with the NIHSS and WBC count but negatively correlated with total cholesterol. Plasma LPS and LBP associate with major causes of ischemic stroke and with ICH, whereas LPS/LBP do not associate with TIAs. LTA only associated with SVO stroke. LPS positively correlated with CRP, LBP, and WBC but negatively correlated with cholesterol. Higher LPS levels were associated with worse stroke outcomes.

Sex differences in the acute and subchronic lung inflammatory responses of mice to nickel nanoparticles

Nickel nanoparticles (NiNPs) are increasingly used in nanotechnology applications, yet information on sex differences in NiNP-induced lung disease is lacking. The goal of this study was to explore mechanisms of susceptibility between male and female mice after acute or subchronic pulmonary exposure to NiNPs. For acute exposure, male and female mice received a single dose of NiNPs with or without LPS by oropharyngeal aspiration and were necropsied 24 h later. For subchronic exposure, mice received NiNPs with or without LPS six times over 3 weeks prior to necropsy. After acute exposure to NiNPs and LPS, male mice had elevated cytokines (CXCL1 and IL-6) and more neutrophils in bronchoalveolar lavage fluid (BALF), along with greater STAT3 phosphorylation in lung tissue. After subchronic exposure to NiNPs and LPS, male mice exhibited increased monocytes in BALF. Moreover, subchronic exposure of male mice to NiNP only induced higher CXCL1 and CCL2 in BALF along with increased alveolar infiltrates and CCL2 in lung tissue. STAT1 in lung tissue was induced by subchronic exposure to NiNPs in females but not males. Males had a greater induction of IL-6 mRNA in liver after acute exposure to NiNPs and LPS, and greater CCL2 mRNA in liver after subchronic NiNP exposure. These data indicate that susceptibility of males to acute lung inflammation involves enhanced neutrophilia with increased CXCL1 and IL-6/STAT3 signaling, whereas susceptibility to subchronic lung inflammation involves enhanced monocytic infiltration with increased CXCL1 and CCL2. STAT transcription factors appear to play a role in these sex differences. This study demonstrates sex differences in the lung inflammatory response of mice to NiNPs that has implications for human disease.

Performance evaluation of high-volume electret filter air samplers in aerosol microbiome research

BACKGROUND

Reliable identification and quantification of bioaerosols is fundamental in aerosol microbiome research, highlighting the importance of using sampling equipment with well-defined performance characteristics. Following advances in sequencing technology, shotgun metagenomic sequencing (SMS) of environmental samples is now possible. However, SMS of air samples is challenging due to low biomass, but with the use of high-volume air samplers sufficient DNA yields can be obtained. Here we investigate the sampling performance and comparability of two hand-portable, battery-operated, high-volume electret filter air samplers, SASS 3100 and ACD-200 Bobcat, previously used in SMS-based aerosol microbiome research.

RESULTS

SASS and Bobcat consistently delivered end-to-end sampling efficiencies > 80% during the aerosol chamber evaluation, demonstrating both as effective high-volume air samplers capable of retaining quantitative associations. Filter recovery efficiencies were investigated with manual and sampler-specific semi-automated extraction procedures. Bobcat semi-automated extraction showed reduced efficiency compared to manual extraction. Bobcat tended towards higher sampling efficiencies compared to SASS when combined with manual extraction. To evaluate real-world sampling performance, side-by-side SASS and Bobcat sampling was done in a semi-suburban outdoor environment and subway stations. SMS-based microbiome profiles revealed that highly abundant bacterial species had similar representation across samplers. While alpha diversity did not vary for the two samplers, beta diversity analyses showed significant within-pair variation in subway samples. Certain species were found to be captured only by one of the two samplers, particularly in subway samples.

CONCLUSIONS

SASS and Bobcat were both found capable of collecting sufficient aerosol biomass amounts for SMS, even at sampling times down to 30 min. Bobcat semi-automated filter extraction was shown to be less effective than manual filter extraction. For the most abundant species the samplers were comparable, but systematic sampler-specific differences were observed at species level. This suggests that studies conducted with these highly similar air samplers can be compared in a meaningful way, but it would not be recommended to combine samples from the two samplers in joint analyses. The outcome of this work contributes to improved selection of sampling equipment for use in SMS-based aerosol microbiome research and highlights the importance of acknowledging bias introduced by sampling equipment and sample recovery procedures.

Respiratory diseases and allergy in farmers working with livestock: a EAACI position paper

Farmers constitute a large professional group worldwide. In developed countries farms tend to become larger, with a concentration of farm operations. Animal farming has been associated with negative respiratory effects such as work-related asthma and rhinitis. However, being born and raised or working on a farm reduces the risk of atopic asthma and rhinitis later in life. A risk of chronic bronchitis and bronchial obstruction/COPD has been reported in confinement buildings and livestock farmers. This position paper reviews the literature linking exposure information to intensive animal farming and the risk of work-related respiratory diseases and focuses on prevention. Animal farming is associated with exposure to organic dust containing allergens and microbial matter including alive microorganisms and viruses, endotoxins and other factors like irritant gases such as ammonia and disinfectants. These exposures have been identified as specific agents/risk factors of asthma, rhinitis, chronic bronchitis, COPD and reduced FEV₁. Published studies on dust and endotoxin exposure in livestock farmers do not show a downward trend in exposure over the last 30 years, suggesting that the workforce in these industries is still overexposed and at risk of developing respiratory disease. In cases of occupational asthma and rhinitis, avoidance of further exposure to causal agents is recommended, but it may not be obtainable in agriculture, mainly due to socio-economic considerations. Hence, there is an urgent need for focus on farming exposure in order to protect farmers and others at work in these and related industries from developing respiratory diseases and allergy.

S1P1 Contributes to Endotoxin-enhanced B-Cell Functions Involved in Hypersensitivity Pneumonitis

In a proportion of patients with hypersensitivity pneumonitis, the biological and environmental factors that sustain inflammation are ill defined, resulting in no effective treatment option. Bioaerosols found in occupational settings are complex and often include Toll-like receptor ligands, such as endotoxins. How Toll-like receptor ligands contribute to the persistence of hypersensitivity pneumonitis, however, remains poorly understood. In a previous study, we found that an S1P₁ (sphingosine-1-phosphate receptor 1) agonist prevented the reactivation of antigen-driven B-cell responses in the lung. Here, we assessed the impact of endotoxins on B-cell activation in preexisting hypersensitivity pneumonitis and the role of S1P₁ in this phenomenon. The impact of endotoxins on pre-established hypersensitivity pneumonitis was studied in vivo. S1P₁ levels were tracked on B cells in the course of the disease using S1P₁-eGFP knockin mice, and the role of S1P₁ on B-cell functions was assessed using pharmacological tools. S1P₁ was found on B cells in experimental hypersensitivity pneumonitis. Endotoxin exposure enhanced neutrophil accumulation in the BAL of mice with experimental hypersensitivity pneumonitis. This was associated with enhanced CD69 cell-surface expression on lymphocytes in the BAL. In isolated B cells, endotoxins increased cell-surface levels of costimulatory molecules and CD69, which was prevented by an S1P₁ agonist. S1P₁ modulators also reduced TNF production by B cells and their capacity to trigger T-cell cooperation ex vivo. An S1P₁ ligand directly inhibited endotoxin-induced B-cell activation.

Bioaerosol Sampling: Classical Approaches, Advances, and Perspectives

Bioaerosol sampling is an essential and integral part of any bioaerosol investigation. Since bioaerosols are very diverse in terms of their sizes, species, biological properties, and requirements for their detection and quantification, bioaerosol sampling is an active, yet challenging research area. This paper was inspired by the discussions during the 2018 International Aerosol Conference (IAC) (St. Louis, MO) regarding the need to summarize the current state of the art in bioaerosol research, including bioaerosol sampling, and the need to develop a more standardized set of guidelines for protocols used in bioaerosol research. The manuscript is a combination of literature review and perspectives: it discusses the main bioaerosol sampling techniques and then overviews the latest technical developments in each area; the overview is followed by the discussion of the emerging trends and developments in the field, including personal sampling, application of passive samplers, and advances toward improving bioaerosol detection limits as well as the emerging challenges such as collection of viruses and collection of unbiased samples for bioaerosol sequencing. The paper also discusses some of the practical aspects of bioaerosol sampling with particular focus on sampling aspects that could lead to bioaerosol determination bias. The manuscript concludes by suggesting several goals for bioaerosol sampling and development community to work towards and describes some of the grand bioaerosol challenges discussed at the IAC 2018.

Occupational Exposure to Endotoxin along a Municipal Scale Fecal Sludge Collection and Resource Recovery Process in Kigali, Rwanda

Background: Little is known about occupational exposures that occur along fecal sludge collection and resource recovery processes. This study characterizes inhaled endotoxin exposure to workers of a municipal scale fecal sludge-to-fuel processes in Kigali, Rwanda. Methods: Forty-two task-based air samples were collected from workers in five tasks along the fecal sludge collection and resource recovery process. Samples were processed for endotoxin using the limulus amebocyte lysate (LAL) test. To account for exposure variability and compare measured concentrations to established exposure limits, we used Monte Carlo modeling methods to construct distributions representing full eight-hour (8-h) exposures to endotoxin across eight exposure scenarios. Results: Geometric mean (GM) endotoxin concentrations in task-based samples ranged from 11–3700 EU/m³ with exposure concentrations increasing as the dryness of the fecal sludge increased through processing. The thermal dryer task had the highest endotoxin concentrations (GM = 3700 EU/m³) and the inlet task had the lowest (GM = 11 EU/m³). The geometric means (GM) of modeled 8-h exposure concentrations were between 6.7–960 EU/m³ and highest for scenarios which included the thermal dryer task in the exposure scenario. Conclusions: Our data suggest the importance of including worker exposure considerations in the design of nascent fecal sludge management processes. The methods used in this study combine workplace sampling with stochastic modeling and are useful for exposure assessment in resource constrained contexts.

Inhalable and Respirable Particulate and Endotoxin Exposures in Kentucky Equine Farms

Adverse respiratory health effects in the agricultural industry have been linked to particulate endotoxin exposure. However, whether the endotoxin concentration is significantly correlated to the size of the particle remains an open question. To date, limited research has been conducted to assess particulate endotoxin exposures in the agricultural industry in general or the equine industry in particular. A task-based exposure assessment was conducted to characterize the endotoxin levels of inhalable and respirable particles on four Kentucky farms during the summer season. We conducted personal sampling of respirable and inhalable particles (n = 75) across all four farms and particulate endotoxin (n = 58) on two of them. Simultaneously, we collected real-time area samples across all four farms by task - horse care, filing hooves, cleaning stalls, cleaning barns, cleaning dry lots, and cleaning trucks. The endotoxin concentration of inhalable particles (geometric mean: 50.2-1,024 EU/m³) was ~50 times higher than that of respirable particles (geometric mean: 1.72-19.0 EU/m³). Horse care generated the lowest endotoxin concentrations for both particle sizes, while cleaning tasks tended to produce higher concentrations. There was no significant correlation between the endotoxin and particle concentrations for each size fraction based on tasks by farm (R² = 0.069 for inhalable; 0.214 for respirable). The equine workers in this study were exposed to higher endotoxin concentrations than workers in other industries, such as the swine industry. Providing exposure control guidelines and recommendations to the equine industry is necessary to reduce long-term endotoxin exposure and to prevent adverse respiratory symptoms.

Surface Energy of Filtration Media Influencing the Filtration Performance against Solid Particles, Oily Aerosol, and Bacterial Aerosol

Particulate airborne pollutants are a big concern to public health, and it brings growing attention about effective filtration devices. Especially, particulate matters smaller than 2.5 µm can reach the thoracic region and the blood stream, and the associated health risk can be exacerbated when pathogenic microbials are present in the air. This study aims at understanding the surface characteristics of nonwoven media that influence filtration performance against solid particles (sodium chloride, NaCl), oily aerosol (dioctyl phthalate, DOP), and Staphylococcus aureus (S. aureus) bacteria. Nonwoven media of polystyrene (PS) fibers were fabricated by electrospinning and its pristine surface energy (38.5 mN/m) was modified to decrease (12.3 mN/m) by the plasma enhanced chemical vapor deposition (PECVD) of octafluorocyclobutane (C4F8) or to increase (68.5 mN/m) by the oxygen (O2) plasma treatment. For NaCl particles and S. aureus aerosol, PS electrospun web showed higher quality factor than polypropylene (PP) meltblown electret that is readily available for commercial products. The O2 plasma treatment of PS media significantly deteriorated the filtration efficiency, presumably due to the quick dissipation of static charges by the O2 plasma treatment. The C4F8 treated, fluorinated PS media resisted quick wetting of DOP, and its filtration efficiency for DOP and S. aureus remained similar while its efficiency for NaCl decreased. The findings of this study will impact on determining relevant surface treatments for effective particulate filtration. As this study examined the instantaneous performance within 1-2 min of particulate exposure, and the further study with the extended exposure is suggested.

Sources of Airborne Endotoxins in Ambient Air and Exposure of Nearby Communities—A Review

Endotoxin is a bioaerosol component that is known to cause respiratory effects in exposed populations. To date, most research focused on occupational exposure, whilst much less is known about the impact of emissions from industrial operations on downwind endotoxin concentrations. A review of the literature was undertaken, identifying studies that reported endotoxin concentrations in both ambient environments and around sources with high endotoxin emissions. Ambient endotoxin concentrations in both rural and urban areas are generally below 10 endotoxin units (EU) m−3; however, around significant sources such as compost facilities, farms, and wastewater treatment plants, endotoxin concentrations regularly exceeded 100 EU m−3. However, this is affected by a range of factors including sampling approach, equipment, and duration. Reported downwind measurements of endotoxin demonstrate that endotoxin concentrations can remain above upwind concentrations. The evaluation of reported data is complicated due to a wide range of different parameters including sampling approaches, temperature, and site activity, demonstrating the need for a standardised methodology and improved guidance. Thorough characterisation of ambient endotoxin levels and modelling of endotoxin from pollution sources is needed to help inform future policy and support a robust health-based risk assessment process.

Changes in gene expression in chronic allergy mouse model exposed to natural environmental PM2.5-rich ambient air pollution

Particulate matter (PM) air pollution has been associated with an increase in the incidence of chronic allergic diseases; however, the mechanisms underlying the effect of exposure to natural ambient air pollution in chronic allergic diseases have not been fully elucidated. In the present study, we aimed to investigate the cellular responses induced by exposure to natural ambient air pollution, employing a mouse model of chronic allergy. The results indicated that exposure to ambient air pollution significantly increased the number of eosinophils in the nasal mucosa. The modulation of gene expression profile identified a set of regulated genes, and the Triggering Receptor Expressed on Myeloid cells1(TREM1) signaling canonical pathway was increased after exposure to ambient air pollution. In vitro, PM2.5 increased Nucleotide-binding oligomerization domain-containing protein 1 (Nod1) and nuclear factor (NF)-κB signaling pathway activation in A549 and HEK293 cell cultures. These results suggest a novel mechanism by which, PM2.5 in ambient air pollution may stimulate the innate immune system through the PM2.5-Nod1-NF-κB axis in chronic allergic disease.

Neuropilin-2 regulates airway inflammatory responses to inhaled lipopolysaccharide

Neuropilins are multifunctional receptors that play important roles in immune regulation. Neuropilin-2 (NRP2) is expressed in the lungs, but whether it regulates airway immune responses is unknown. Here, we report that Nrp2 is weakly expressed by alveolar macrophages (AMs) in the steady state but is dramatically upregulated following in vivo lipopolysaccharide (LPS) inhalation. Ex vivo treatment of human AMs with LPS also increased NRP2 mRNA expression and cell-surface display of NRP2 protein. LPS-induced Nrp2 expression in AMs was dependent upon the myeloid differentiation primary response 88 signaling pathway and the transcription factor NF-κB. In addition to upregulating display of NRP2 on the cell membrane, inhaled LPS also triggered AMs to release soluble NRP2 into the airways. Finally, myeloid-specific ablation of NRP2 resulted in increased expression of the chemokine (C-C motif) ligand 2 ( Ccl2) in the lungs and prolonged leukocyte infiltration in the airways following LPS inhalation. These findings suggest that NRP2 expression by AMs regulates LPS-induced inflammatory cell recruitment to the airways and reveal a novel role for NRP2 during innate immune responses in the lungs.

Size, Composition, and Source Profiles of Inhalable Bioaerosols from Colorado Dairies

Particulate matter emissions from agricultural livestock operations contain both chemical and biological constituents that represent a potential human health hazard. The size and composition of these dusts, however, have not been well described. We evaluated the full size distribution (from 0 to 100 μm in aerodynamic diameter) and chemical/biological composition of inhalable dusts inside several Colorado dairy parlors. Four aerodynamic size fractions (<3, 3-10, 10-30, and >30 μm) were collected and analyzed using a combination of physiochemical techniques to understand the structure of bacterial communities and chemical constituents. Airborne particulate mass followed a bimodal size distribution (one mode at 3 μm and a second above 30 μm), which also correlated with the relative concentrations of the following microbiological markers: bacterial endotoxin, 3-hydroxy fatty acids, and muramic acid. Sequencing of the 16S-rRNA components of this aerosol revealed a microbiome derived predominantly from animal sources. Bacterial genera included Staphlyococcus, Pseudomonas, and Streptococcus, all of which have proinflammatory and pathogenic capacity. Our results suggest that the size distribution of bioaerosols emitted by dairy operations extends well above 10 μm in diameter and contains a diverse mixture of potentially hazardous constituents and opportunistic pathogens. These findings should inform the development of more effective emissions control strategies.

Occupational exposure to endotoxins and lung cancer risk: results of the ICARE Study

Objectives

To investigate the role of occupational exposure to endotoxins in lung cancer in a French population-based case–control study (ICARE (Investigation of occupational and environmental causes of respiratory cancers)).

Methods

Detailed information was collected on the occupational history and smoking habits from 2926 patients with histologically confirmed lung cancer and 3555 matched controls. We evaluated each subject’s endotoxin exposure after cross referencing International Standard Classification of Occupations (ISCO) codes (for job tasks) and Nomenclature d'Activités Françaises (NAF) codes (for activity sectors). Endotoxin exposure levels were attributed to each work environment based on literature reports. ORs and 95% CIs were estimated using unconditional logistic regression models and controlled for main confounding factors.

Results

An inverse association between exposure to endotoxins and lung cancer was found (OR=0.80, 95% CI 0.66 to 0.95). Negative trends were shown with duration and cumulative exposure, and the risk was decreased decades after exposure cessation (all statistically significant). Lung cancer risk was particularly reduced among workers highly exposed (eg, in dairy, cattle, poultry, pig farms), but also in those weakly exposed (eg, in waste treatment). Statistically significant interactions were shown with smoking, and never/light smokers were more sensitive to an endotoxin effect than heavy smokers (eg, OR=0.14, 95% CI 0.06 to 0.32 and OR=0.80, 95% CI 0.45 to 1.40, respectively, for the quartiles with the highest cumulative exposure, compared with those never exposed). Pronounced inverse associations were shown with adenocarcinoma histological subtype (OR=0.37, 95% CI 0.25 to 0.55 in the highly exposed).

Conclusions

Our findings suggest that exposure to endotoxins, even at a low level, reduces the risk of lung cancer.

Modification of sample processing for the Limulus amebocyte lysate assay enhances detection of inflammogenic endotoxin in intact bacteria and organic dust

The pro-inflammatory potency and causal relationship with asthma of inhaled endotoxins have underscored the importance of accurately assessing the endotoxin content of organic dusts. The Limulus amebocyte lysate (LAL) assay has emerged as the preferred assay, but its ability to measure endotoxin in intact bacteria and organic dusts with similar sensitivity as purified endotoxin is unknown. We used metabolically radiolabeled Neisseria meningitidis and both rough and smooth Escherichia coli to compare dose-dependent activation in the LAL with purified endotoxin from these bacteria and shed outer membrane (OM) blebs. Labeled [14C]-3-OH-fatty acids were used to quantify the endotoxin content of the samples. Purified meningococcal and E. coli endotoxins and OM blebs displayed similar specific activity in the LAL assay to the purified LPS standard. In contrast, intact bacteria exhibited fivefold lower specific activity in the LAL assay but showed similar MD-2-dependent potency as purified endotoxin in inducing acute airway inflammation in mice. Pre-treatment of intact bacteria and organic dusts with 0.1 M Tris-HCl/10 mM EDTA increased by fivefold the release of endotoxin. These findings demonstrate that house dust and other organic dusts should be extracted with Tris/EDTA to more accurately assess the endotoxin content and pro-inflammatory potential of these environmental samples.

Electrostatic dust collectors compared to inhalable samplers for measuring endotoxin concentrations in farm homes

Paired electrostatic dust collectors (EDCs) and daily, inhalable button samplers (BS) were used concurrently to sample endotoxin in 10 farm homes during 7-day periods in summer and winter. Winter sampling included an optical particle counter (OPC) to measure PM2.5 and PM2.5-10 . Electrostatic dust collectors and BS filters were analyzed for endotoxin using the kinetic chromogenic Limulus amebocyte lysate assay. Optical particle counter particulate matter (PM) data were divided into two PM categories. In summer, geometric mean (geometric standard deviation) endotoxin concentrations were 0.82 EU/m(3) (2.7) measured with the BS and 737 EU/m(2) (1.9) measured with the EDC. Winter values were 0.52 EU/m(3) (3.1) for BS and 538 EU/m(2) (3.0) for EDCs. Seven-day endotoxin values of EDCs were highly correlated with the 7-day BS sampling averages (r = 0.70; P < 0.001). Analysis of variance indicated a 2.4-fold increase in EDC endotoxin concentrations for each unit increase of the ratio of PM2.5 to PM2.5-10 . There was also a significant correlation between BS and EDCs endotoxin concentrations for winter (r = 0.67; P < 0.05) and summer (r = 0.75; P < 0.05). Thus, EDCs sample comparable endotoxin concentrations to BS, making EDCs a feasible, easy to use alternative to BS for endotoxin sampling.

Air-sampled Filter Analysis for Endotoxins and DNA Content

Outdoor aerosol research commonly uses particulate matter sampled on filters. This procedure enables various characterizations of the collected particles to be performed in parallel. The purpose of the method presented here is to obtain a highly accurate and reliable analysis of the endotoxin and DNA content of bio-aerosols extracted from filters. The extraction of high molecular weight organic molecules, such as lipopolysaccharides, from sampled filters involves shaking the sample in a pyrogen-free water-based medium. The subsequent analysis is based on an enzymatic reaction that can be detected using a turbidimetric measurement. As a result of the high organic content on the sampled filters, the extraction of DNA from the samples is performed using a commercial DNA extraction kit that was originally designed for soils and modified to improve the DNA yield. The detection and quantification of specific microbial species using quantitative polymerase chain reaction (q-PCR) analysis are described and compared with other available methods.

Profiling of 3-hydroxy fatty acids as environmental markers of endotoxin using liquid chromatography coupled to tandem mass spectrometry

3-Hydroxy acids are constituents of the lipid A part of lipopolysaccharides and may potentially be used as chemical markers of endotoxin. While commercial enzymatic assays, such as the widely used Limulus amebocyte lysate (LAL) assay, commonly detect merely the water-soluble fraction of the bioactive endotoxin, the chemical approach aims to estimate the total amount of endotoxin present in a sample. Our objective was to develop a simple method for quantitative profiling of 3-hydroxy fatty acids in occupational and environmental samples based on detection with HPLC-MS/MS. We included eleven 3-hydroxy fatty acids (3-hydroxyoctanoic acid to 3-hydroxyoctadecanoic acid) in the HPLC-MS/MS based method, which involved base hydrolysis of filter samples using 1M sodium hydroxide and removal of the base as well as concentration of the fatty acids using solid-phase extraction on a functionalized polystyrene-divinylbenzene polymer. Recovery trials from spiked glass fiber filters, using threo-9,10-dihydroxyhexadecanoic acid as internal standard, gave an overall recovery of 54-86% for 3-hydroxy fatty acids of medium chain length (3-hydroxynonanoic to 3-hydroxypentadecanoic acid). 3-Hydroxyoctanoic acid and the longer chain fatty acids were more problematic yielding overall spike recoveries of 11-39%. While the 3-hydroxy fatty acid profile of pure lipopolysaccharides was dominated by 3-hydroxydecanoic, 3-hydroxydodecanoic and 3-hydroxytetradecanoic acid the aqueous phase from drilling mud contained in addition relatively high amounts of 3-hydroxyoctanoic and 3-hydroxynonanoic acid. Endotoxin activity as measured by the LAL assay was reasonably correlated (R(2)=0.54) to the sum of 3-hydroxydecanoic acid, 3-hydroxydodecanoic acid and 3-hydroxytetradecanoic acid in these samples.

Evaluation of exposure-response relationships for health effects of microbial bioaerosols - A systematic review

Studies suggest adverse health effects following exposure to bioaerosols in the environment and in particular at workplaces. However, there is still a lack of health-related exposure limits based on toxicological or epidemiological studies from environmental health or from the working environment. The aim of this study was to derive health-based exposure limits for bioaerosols that can protect the general population as group "at risk" via environmental exposure using analysis of peer-reviewed studies related to occupational medicine, indoor air and environmental health. The derivation of exposure limits should be conducted by the members of a bioaerosol expert panel according to established toxicological criteria. A systematic review was performed in Medline (PubMed) including studies containing both data on exposure measurements and observed health outcomes. In addition, literature recommended by the experts was considered. A comprehensive search strategy was generated and resulted in a total of n=1569 studies in combination with the literature recommendations. Subsequently, abstracts were screened using defined exclusion criteria yielding a final number of n=44 studies. A standardized extraction sheet was used to combine data on health effects and exposure to different bioaerosols. After full-text screening and extraction according to the defined exclusion criteria n=20 studies were selected all related to occupational exposures comprising the working areas wood processing, farming, waste processing and others. These studies were analyzed in collaboration with the bioaerosol expert network in terms of suitability for derivation of health-related exposure limits. The bioaerosol expert network concluded that none of the analyzed studies provided suitable dose-response relationships for derivation of exposure limits. The main reasons were: (1) lack of studies with valid dose-response data; (2) diversity of employed measuring methods for microorganisms and bioaerosol-emitting facilities; (3) heterogeneity of health effects; (4) insufficient exposure assessment. However, several indicator parameters and exposure concentrations could be identified for different bioaerosol-emitting facilities. Nevertheless, health-related exposure limits are urgently needed especially in approval procedures of facilities like composting plants or livestock farms emitting bioaerosols in the neighbourhood of residents. In the regulatory toxicology framework, it is common to use animal experimental studies for derivation of general exposure limits if appropriate environmental epidemiological studies on harmful substances are lacking. This might be another possibility to obtain health-related exposure limits for specific bioaerosol parameters. Furthermore, we recommend to use suitable measurable outcome parameters related to bioaerosols; to measure bioaerosols according to a protocol representative for exposure pattern and duration at the particular work place; to develop standardized detection methods for indicator parameters; to combine different detection methods to compensate for the limitations of each method; to apply new analysis methods to identify the real risk potential.

Industrial hygiene, occupational safety and respiratory symptoms in the Pakistani cotton industry

OBJECTIVES

In the cotton industry of Pakistan, 15 million people are employed and exposed to cotton dust, toxic chemicals, noise and physical hazards. The aim of this study was to determine the prevalence of health symptoms, particularly respiratory symptoms, and to measure cotton dust and endotoxin levels in different textile factories of Faisalabad, Pakistan.

METHODS

A cross-sectional investigation was performed in a representative sample of 47 cotton factories in the Faisalabad region in Punjab, Pakistan. Respiratory symptoms of 800 workers were documented by questionnaire. Occupational safety in the factories was assessed by a trained expert following a checklist, and dust and endotoxin levels in different work areas were measured.

RESULTS

Prevalence of respiratory disease symptoms (fever, shortness of breath, chest tightness and cough) was generally high and highest in the weaving section of the cotton industry (20-40% depending on symptoms). This section also displayed the poorest occupational safety ratings and the highest levels of inhalable cotton dust (mean±SD 4.6±2.5 vs 0.95±0.65 mg/m(3) in compact units). In contrast, endotoxin levels were highest in the spinning section (median 1521 EU/m(3)), where high humidity is maintained.

CONCLUSIONS

There are still poor working conditions in the cotton industry in Pakistan where workers are exposed to different occupational hazards. More health symptoms were reported from small weaving factories (power looms). There is a dire need for improvements in occupational health and safety in this industrial sector with particular focus on power looms.

Molecular characterization of microbial communities in bioaerosols of a coal mine by 454 pyrosequencing and real-time PCR

Microbial diversity and abundance in bioaerosols of a coal mine were analyzed based on 454 pyrosequencing and real-time polymerase chain reaction (PCR). A total of 37,191 high quality sequences were obtained and could be classified into 531, 1730 and 448 operational taxonomic units respectively for archaea, bacteria and fungi at 97% sequence similarity. The Shannon diversity index for archaea, bacteria and fungi was respectively 4.71, 6.29 and 3.86, indicating a high diversity in coal mine bioaerosols. Crenarchaeota, Proteobacteria and Ascomycota were the dominant phyla for archaea, bacteria and fungi, respectively. The concentrations of total archaea, bacteria and fungi were 1.44×10(8), 1.02×10(8) and 9.60×10(4) cells/m3, respectively. Methanotrophs observed in bioaerosols suggested possible methane oxidation in the coal mine. The identified potential pathogens to coal miners, such as Acinetobacter schindleri, Aeromonas cavernicola, Alternaria alternata, Aspergillus penicillioides, Cladosporium cladosporioides, and Penicillium brevicompactum were also observed. This was the first investigation of microbial diversity and abundance in coal mine bioaerosols. The investigation of microbial communities would be favorable in promoting the progress of methane control based on microbial technique and concern on coal miners' health.

Differential response of human nasal and bronchial epithelial cells upon exposure to size-fractionated dairy dust

Exposure to organic dusts is associated with increased respiratory morbidity and mortality in agricultural workers. Organic dusts in dairy farm environments are complex, polydisperse mixtures of toxic and immunogenic compounds. Previous toxicological studies focused primarily on exposures to the respirable size fraction; however, organic dusts in dairy farm environments are known to contain larger particles. Given the size distribution of dusts from dairy farm environments, the nasal and bronchial epithelia represent targets of agricultural dust exposures. In this study, well-differentiated normal human bronchial epithelial cells and human nasal epithelial cells were exposed to two different size fractions (PM10 and PM>10) of dairy parlor dust using a novel aerosol-to-cell exposure system. Levels of proinflammatory transcripts (interleukin [IL]-8, IL-6, and tumor necrosis factor [TNF]-α) were measured 2 h after exposure. Lactate dehydrogenase (LDH) release was also measured as an indicator of cytotoxicity. Cell exposure to dust was measured in each size fraction as a function of mass, endotoxin, and muramic acid levels. To our knowledge, this is the first study to evaluate the effects of distinct size fractions of agricultural dust on human airway epithelial cells. Our results suggest that both PM10 and PM>10 size fractions elicit a proinflammatory response in airway epithelial cells and that the entire inhalable size fraction needs to be considered when assessing potential risks from exposure to agricultural dusts. Further, data suggest that human bronchial cells respond differently to these dusts than human nasal cells, and therefore that the two cell types need to be considered separately in airway cell models of agricultural dust toxicity.

Endotoxin deposits on the inner surfaces of closed-face cassettes during bioaerosol sampling: a field investigation at composting facilities

A set of 270 bioaerosol samples was taken from 15 composting facilities using polystyrene closed-face filter cassettes (CFCs). The objective was to measure the quantity of endotoxin deposits on the inner surfaces of the cassettes (sometimes referred to as 'wall deposits'). The results show that endotoxins are deposited on the inner surfaces of the CFCs through sampling and/or handling of samples. The quantity of endotoxins measured on inner surfaces range between 0.05 (the limit of detection of the method) and 3100 endotoxin units per cassette. The deposits can represent a large and variable percentage of the endotoxins sampled. More than a third of the samples presented a percentage of inner surface deposits >40% of the total quantity of endotoxins collected (filter + inner surfaces). Omitting these inner surface deposits in the analytical process lead to measurement errors relative to sampling all particles entering the CFC sampler, corresponding to a developing consensus on matching the inhalable particulate sampling convention. The result would be underestimated exposures and could affect the decision as to whether or not a result is acceptable in comparison to airborne concentration limits defined in terms of the inhalability convention. The results of this study suggest including the endotoxins deposited on the inner surfaces of CFCs during analysis. Further researches are necessary to investigate endotoxin deposits on the inner cassette surfaces in other working sectors.

Relationship between chicken cellular immunity and endotoxin levels in dust from chicken housing environments

Hazardous biochemical agents in animal husbandry indoor environments are known to promote the occurrence of various illnesses among workers and animals. The relationship between endotoxin levels in dust collected from chicken farms and various immunological markers was investigated. Peripheral blood was obtained from 20 broiler chickens and 20 laying hens from four different chicken farms in Korea. Concentrations of total or respirable dust in the inside the chicken farm buildings were measured using a polyvinyl chloride membrane filter and mini volume sampler. Endotoxin levels in the dust were determined by the Limulus Amebocyte Lysate Kinetic method. Interferon-γ production by peripheral blood mononuclear cells stimulated with concanavalin A was significantly lower in broilers or layers from the farms with higher endotoxin concentrations than the chickens from the farms with lower endotoxin levels. An opposite pattern was observed for plasma cortisol concentrations with higher cortisol levels found in chickens from the farms with higher endotoxin levels. When peripheral lymphocytes were examined, the percentage of CD3(-)Ia(+) B cells was lower in layers from farms with higher endotoxin levels than those from locations with lower endotoxin levels. Overall, these results suggest a probable negative association between dust endotoxin levels and cell-mediated immunity in chickens.

Dust, endotoxin, fungi, and bacteria exposure as determined by work task, season, and type of plant in a flower greenhouse

BACKGROUND

Greenhouse workers are exposed to dust, endotoxin, fungi, and bacteria potentially causing airway inflammation as well as systemic symptoms. Knowledge about determinants of exposure is a prerequisite for efficient prevention through knowledge-based reduction in exposure. The objective of this study was to assess the occupational exposure in a flower greenhouse and to investigate the impact of work tasks on the intensity and variability in exposure.

METHODS

Seventy-six personal full-shift exposure measurements were performed on 38 employees in a Danish flower greenhouse producing Campanula, Lavandula, Rhipsalideae, and Helleborus. The samples were gravimetrically analysed for inhalable dust. Endotoxin was assessed by the Limulus Amoebocyte Lysate test and culture-based quantification of bacteria and fungi was performed. Information on the performed tasks during sampling was extracted from the greenhouse electronic task logging system. Associations between log-transformed exposure outcomes, season, and work tasks were examined in linear mixed-effects regression with worker identity as random effect.

RESULTS

Measured concentrations ranged between 0.04 and 2.41mg m(-3) for inhalable dust and between 0.84 and 1097 EU m(-3) for endotoxin exposure, with the highest mean levels measured during Lavandula and Campanula handling, respectively. Personal exposure to fungi ranged between 1.8×10(2) and 3.4×10(6) colony-forming units (CFU) m(-3) and to bacteria between 1.6×10(1) and 4.2×10(5) CFU m(-3). Exposure to dust, endotoxin, fungi, and bacteria differed between seasons. Packing Lavandula, sticking, potting, and grading Rhipsalideae, and all examined tasks related to Campanula production except sticking increased dust exposure. Endotoxin exposure was increased during sticking Campanula and pinching or packing Rhipsalideae, and fungi exposure was elevated by subtasks performed in the research and development area for Campanula, and by potting, packing/dumping Campanula. Sticking and working with subtasks in the research and development area for Campanula increased bacteria exposure.

CONCLUSION

This study revealed moderate dust exposure levels compared to the levels observed in other greenhouse productions and other occupations with organic dust exposure such as farming. However, high exposures to bacteria and fungi were detected during selected tasks and the proposed health-based endotoxin exposure limit of 90 EU m(-3) was exceeded in 30% of the samples, which may have health implications for the employees. Exposure levels were found to vary depending on the tasks performed, and thereby results can be used to direct task-based initiatives to reduce workplace exposures.

Assessment of workers' exposure to aflatoxin B1 in a Portuguese waste industry

Aflatoxin B1 (AFB1) is considered by different International Agencies as a genotoxic and potent hepatocarcinogen. However, despite the fact that the fungi producing this compound are detected in some work environments, AFB1 is rarely monitored in occupational settings. The aim of the present investigation was to assess exposure to AFB1 of workers from one Portuguese waste company located in the outskirt of Lisbon. Occupational exposure assessment to AFB1 was done with a biomarker of internal dose that measures AFB1 in the serum by enzyme-linked immunosorbent assay. Forty-one workers from the waste company were enrolled in this study (26 from sorting; 9 from composting; 6 from incineration). A control group (n = 30) was also considered in order to know the AFB1 background levels for the Portuguese population. All the workers showed detectable levels of AFB1 with values ranging from 2.5ng ml(-1) to 25.9ng ml(-1) with a median value of 9.9±5.4ng ml(-1). All of the controls showed values below the method's detection limit. Results obtained showed much higher (8-fold higher) values when compared with other Portuguese settings already studied, such as poultry and swine production. Besides this mycotoxin, other mycotoxins are probably present in this occupational setting and this aspect should be taken into consideration for the risk assessment process due to possible synergistic reactions. The data obtained suggests that exposure to AFB1 occurs in a waste management setting and claims attention for the need of appliance of preventive and protective safety measures.

Investigating the link between particulate exposure and airway inflammation in the horse

Inhalant exposure to airborne irritants commonly encountered in horse stables is implicated in the pathogenesis of inflammatory airway disease (IAD) and recurrent airway obstruction (RAO), non‐infectious, inflammatory pulmonary disorders that impact the health and performance of horses across all equine disciplines. IAD and RAO have overlapping clinical, cytological, and functional manifestations of the pulmonary response to organic dust and noxious gases encountered in the barn environment. Study of these diseases has provided important but incomplete understanding of the effect of air quality upon the respiratory health of horses. In this review, the principles of particulate exposure assessment, including health‐related aerosol size fractions and size‐selective sampling, the factors influencing air quality in equine environments, and the effect of air quality on the equine respiratory tract are discussed. The objective of this review is to provide the reader with a summary of the most common chronic inflammatory airway diseases in the horse and the principles of air sampling that are essential to the planning, interpretation, and assessment of equine respiratory health‐related exposure studies.

Development and evaluation of antimicrobial activated carbon fiber filters using Sophora flavescens nanoparticles

Activated carbon fiber (ACF) filters have a wide range of applications, including air purification, dehumidification, and water purification, due to their large specific surface area, high adsorption capacity and rate, and specific surface reactivity. However, when airborne microorganisms such as bacteria and fungi adhere to the carbon substrate, ACF filters can become a source of microbial contamination, and their filter efficacy declines. Antimicrobial treatments are a promising means of preventing ACF bio-contamination. In this study, we demonstrate the use of Sophora flavescens in antimicrobial nanoparticles coated onto ACF filters. The particles were prepared using an aerosol process consisting of nebulization-thermal drying and particle deposition. The extract from S. flavescens is an effective, natural antimicrobial agent that exhibits antibacterial activity against various pathogens. The efficiency of Staphylococcus epidermidis inactivation increased with the concentration of S. flavescens nanoparticles in the ACF filter coating. The gas adsorption efficiency of the coated antimicrobial ACF filters was also evaluated using toluene. The toluene-removal capacity of the ACF filters remained unchanged while the antimicrobial activity was over 90% for some nanoparticle concentrations. Our results provide a scientific basis for controlling both bioaerosol and gaseous pollutants using antimicrobial ACF filters coated with S. flavescens nanoparticles.

Exposure and preventive measure to reduce high and daily exposure to Bacillus thuringiensis in potted plant production

The bacterium Bacillus thuringiensis (Bt) is the active organism in a variety of commercially available products used worldwide as biopesticides. Bt products are applied in large outdoor areas as well as in indoor environments. Even though it has been sold for decades, not much is known about the occupational exposure to Bt. The aim of this study was to obtain knowledge about the exposure to Bt subspecies israelensis (Bti) in a propagation section in a greenhouse, where Bti is applied hourly by a spray boom, and to test a preventive measure to reduce the exposure to airborne Bti. Furthermore, we wanted to study the exposure during work with potted plants treated earlier with Bti. Exposure to aerosols with Bti was measured repeatedly by personal and stationary samplers before and after the intervention. Bti was identified by polymerase chain reaction in air and soil samples. Personal exposure to inhalable Bti in the propagation section was 3×10(5) cfu m(-3) (median level, n = 22); the personal exposure of people working with plants treated earlier with Bti was 3200 cfu m(-3) (median level, n = 17). The highest single measure was found for the person working with the spray boom (7×10(5) cfu m(-3)) but airborne Bti was present at all sampling stations in the propagation section. Bti constituted a high share of the airborne cultivable bacteria and a smaller share of the soilborne bacteria in the propagation section. In a human cell assay, spiking an aerosol sample with a product with Bti increased the inflammatory potential of an aerosol sample from the greenhouse significantly. Based on the inflammatory potential and the high personal exposure, a cover around the spray boom was built as an attempt to reduce the daily exposure to Bti. The cover reduced the personal exposure to Bti from 3.0×10(5) cfu m(-3) to 1.8×10(4) cfu m(-3). The exposure was thus reduced by a factor 17, which is a considerable reduction. Bti was present in different particle size fractions with the majority, both before and after the intervention, in the fraction of airborne particles with an aerodynamic diameter between 1.2 and 3.0 µm. The measured occupational exposure to Bti is discussed in relation to risk evaluation.

Assessment of workers' exposure to bioaerosols in a French cheese factory

Hundreds of different cheeses are produced in France, where 23.9kg of cheese were consumed per inhabitant in 2009, when it was ranked the second cheese-consuming nation. To meet this considerable demand, a large number of cheese factories exist where many workers, especially cheese washers, may be exposed to fungal bioaerosols that can lead to adverse toxinic and allergic effects. Airborne bacteria, fragments, or microbial by-products (endotoxins) are also found and contribute to total worker exposure. However, there is almost no published data concerning worker exposure or characteristics of bioaerosols emitted during these activities. Here, we measured the parameters (concentrations, species present, and size distribution) of the culturable fungal bioaerosol emitted in a French natural-rind cheese-maturing cellar. Concentrations of airborne bacteria and endotoxins were also measured. The main tasks were investigated using stationary or personal sampling over three consecutive days. Depending on the work area, high concentrations of culturable mesophilic microorganisms were measured (using closed-face cassettes): from 10(4) to 2×10(8) CFU m(-3) for fungi and from 10(3) to 10(6) CFU m(-3) for bacteria. These concentrations are 10- to 100000-fold higher than those measured at two reference points (indoor and outdoor) that are assumed not to be contaminated by the plant's activities. Endotoxin concentrations were between 10 and 300 EU m(-3) in the plant. Exposure was further assessed by identifying the predominant culturable fungi (allergenic Mucor fuscus and Penicillium sp.) and by measuring particle size distributions (cascade impactor). Airborne fungal entities (spores, mycelium strands and fragments, agglomerates, etc.) were found with aerodynamic diameters from 3 to over 20 µm. A metrological approach was used to fully characterize the culturable fungal aerosols generated during cheese maturing in this plant. The results show that workers are exposed to concentrations of airborne culturable fungi, sometimes very high, throughout the manufacturing process. In addition to fungi, culturable bacteria and endotoxins are also present in the work atmosphere. All these microbial organisms thus contribute in a complex manner to total worker exposure. Despite the lack of both occupational exposure limit values and standardized measuring methods, our results suggest that an immunological risk may occur among workers, especially for cheese brushers, cheese washers, and packagers who are the most exposed workers in the factory.

Environmental exposures and airway inflammation in young thoroughbred horses

Background

Inflammatory airway disease (IAD) in horses is a widespread, performance‐limiting syndrome believed to develop in response to inhaled irritants in the barn environment.

Objectives

To evaluate changes in bronchoalveolar lavage fluid (BALF) cytology and exposure to particulates, endotoxin, and ammonia during horses' first month in training.

Animals

Forty‐nine client‐owned 12‐ to 36‐month‐old Thoroughbred horses entering race training.

Methods

In this prospective cohort study, a convenience sample of horses was assigned to be fed hay from a net (n = 16), whereas the remaining horses were fed hay from the ground (n = 33). BALF was collected at enrollment and after 14 and 28 days in training. Respirable particulate, inhalable particulate, respirable endotoxin, and ammonia concentrations were measured at the breathing zone of each horse weekly.

Results

Median respirable particulates were significantly higher when horses were fed from hay nets than when fed hay from the ground (hay net 0.28 mg/m³, no hay net 0.055 mg/m³, P < .001). Likewise, inhalable particulate (hay net 8.3 mg/m³, no hay net 3.3 mg/m³, P = .0064) and respirable endotoxin (hay net 173.4 EU/m³, no hay net 59.2 EU/m³, P = .018) exposures were significantly higher when horses were fed from hay nets. Feeding hay from a net resulted in significantly higher BALF eosinophil proportions over time (P < .001). BALF eosinophils were significantly related to respirable particulate exposure (14 days in training r_s = 0.37, P = .012, 28 days in training, r_s = 0.38, P = .017).

Conclusions and Clinical Importance

Pulmonary eosinophilic inflammation develops in response to respirable particulate exposure in young Thoroughbreds, indicating a potential hypersensitivity to inhaled particulate allergens.

Exposure to airborne endotoxins among sewer workers: an exploratory study

Exploratory bioaerosol sampling was performed in order to assess exposure to airborne endotoxins during sewer work. Personal samples were collected in underground sewer pipes using 37-mm closed-face cassettes containing fibreglass filters (CFC-FG method) or polycarbonate filters (CFC-PC method). Endotoxins were quantified using the limulus amoebocyte lysate assay. Concentrations of airborne endotoxins at sewer workplaces (16-420 EU m(-3)) were higher than those measured outside the sewer network (0.6-122 EU m(-3)). Sewer worker exposure to airborne endotoxins depended on the workplace and on the tasks. Exposure levels were the highest for tasks involving agitation of water and matter, especially for 'chamber cleanup' and 'pipes cleanup' with a high-pressure water jet. Airborne endotoxin levels at the workplace tended to be higher when CFC-FG was used as the sampling method rather than CFC-PC. The adjusted mean of the measured concentrations for CFC-PC represents 57% of the mean observed with CFC-FG. The number of samples collected in the descriptive study was too low for drawing definitive conclusions and further exposure investigations are needed. Therefore, our exploratory study provides new exposure data for the insufficiently documented sewer working environment and it would be useful for designing larger exposures studies.