Corn Dust Research Articles

Characteristics of dust explosion venting pressure and flame under high activation pressure

A 20 L spherical explosive device with a venting diameter of 110 mm was used to study the vented pressure and flame propagation characteristics of corn dust explosion with an activation pressure of 0.78–2.1 bar and a dust concentration of 400∼900 g/m3. And the formation and prevention of secondary vented flame are analyzed and discussed. The results show that the maximum reduced explosion overpressure increases with the activation pressure, and the vented flame length and propagation speed increase first and then decrease with time. The pressure and flame venting process models are established, and the region where the secondary flame occurs is predicted. Whether there is pressure accompanying or not in the venting process, the flame venting process is divided into two stages: overpressure venting and normal pressure venting. In the overpressure venting stage, the flame shape gradually changes from under-expanded jet flame to turbulent jet flame. In the normal pressure venting stage, the flame form is a turbulent combustion flame, and a secondary flame occurs under certain conditions. The bleed flames within the test range are divided into three regions and four types according to the shape of the flame and whether there is a secondary flame. The analysis found that when the activation pressure is 0.78 bar and the dust concentration is less than 500 g/m3, there will be no secondary flame. Therefore, to prevent secondary flames, it is necessary to reduce the activation pressure and dust concentration. When the dust concentration is greater than 600 g/m3, the critical dust concentration of the secondary flame gradually increases with the increase of the activation pressure. Therefore, when the dust concentration is not controllable, a higher activation pressure can be selected based on comprehensive consideration of the activation pressure and destruction pressure of the device to prevent the occurrence of the secondary flame.

53 Evaluating the Efficacy of Boot Baths with Wet and Dry Disinfectants for Porcine Epidemic Diarrhea Virus and Porcine Reproductive and Respiratory Syndrome Virus

Abstract Maintaining biosecurity between barns is challenging. Boot baths, either wet or dry, can be implemented to limit pathogen spread. The objective was to evaluate the efficacy of boot baths using wet or dry disinfectants for porcine epidemic diarrhea virus (PEDV) and porcine reproductive and respiratory syndrome virus (PRRSV). Treatments included 1) control, 2) wet disinfectant (Synergize, Neogen, Lexington, KY), and 3) dry disinfectant (Traffic C.O.P., PSP, LLC, Rainsville, AL). Prior to disinfection, 0.5 mL of both PRRSV (~1×105 TCID50/mL) and PEDV (~1×105 TCID50/mL) was placed onto a new boot with a layer of autoclaved corn dust and allowed to dry for 15 minutes. After the mixture dried, the boot was put on and stepped into its respective boot bath. After 3 seconds, the boot was lifted out of the bath and stepped onto a stainless-steel coupon to simulate walking through a facility. Both boot and coupon were allowed to dry for 1 minute before swabs were taken from both surfaces. Samples were analyzed in a duplex PCR at the Kansas State Veterinary Diagnostic Laboratory. Cycle threshold values were analyzed using SAS GLIMMIX v 9.4 (SAS, Inc., Cary, NC). There was no evidence of a treatment×surface×virus interaction (P > 0.10). The interaction between treatment×surface impacted (P < 0.05) the quantity of detectable RNA. The control had greater concentration of virus on the coupon than the boot. The reverse was true for boots treated with wet disinfectant, where the boot had a greater concentration of virus than the coupon. Treatment×virus also impacted detectable RNA (P < 0.05), where wet and control boots had greater quantities of PEDV RNA than PRRSV. There was no detectable virus when dry disinfectant was used. For this trial, dry disinfectant was the most efficacious in reducing the viral RNA on both boots and subsequent surfaces; however, further research in commercial settings is warranted.

Modelling of the minimum ignition temperature (MIT) of corn dust using statistical analysis and artificial neural networks based on the synergistic effect of concentration and dispersion pressure

Corn dust is a highly energetic substance and frequently found in the food manufacturing industries. It not only poses occupational safety hazards such as suffocation or lung disorders for exposed persons but is often extremely explosible in ignition sensitive environment. This probability of explosion can be assessed and minimised with in-depth knowledge of controlling parameters/physical properties that trigger the ignition. This research takes into account the minimum ignition temperature (MIT), which is the control parameter for explosion risk assessment. MIT relies on multiple factors, such as moisture content, particle size, dust concentration, dispersion pressure, humidity and environmental temperature. In this study, the ignition of corn dust clouds was analysed using a Godbert Greenwald furnace for different combinations of dispersion pressure and concentrations. Test findings revealed that the minimum ignition temperature rises with a decrease in particle size. However, the minimum ignition temperature decreases with increased dispersion pressure and concentration until a specific value known as optimal value for ignition. Moreover, this work focuses on a statistical approach of polynomial surface fitting to forecast the MIT based on the combined impact of concentration and dispersion pressure on MIT for corn dust in a real-time experiment. The minimum value of the Bayesian Information Criterion (BIC) was used to select the most appropriate polynomial model due to its authenticity and strong reputation. An artificial neural network (ANN) is also used as a predictive tool to develop a model that can forecast the MIT with a defined combination of dispersion pressures and corn dust concentrations. As soon as an appropriate estimation of this minimum ignition temperature of the combustible dust is confirmed, it is possible to ensure that the temperatures of the surrounding hot surfaces do not rise to that point to prevent the explosion. The predictive results obtained from ANN were found to be good when compared with the polynomial surface fit. Several models with different numbers of neurons have been trained with different transfer functions. For the training, validation, and test phases, R values are around 1.0, i.e., 0.9863, 0.9930, and 0.9893, respectively. The overall R value was 0.9875 for the proposed network. The findings were considered to be acceptable as the overall value of R was close to 1.0. The network obtained sufficiently comparable findings with the research conducted by Kasalova and Balog.

Combined Effect of Dispersion Pressure and Concentration on Minimum Ignition Temperature of Corn Dust using Response Surface Methodology – Preliminary Investigation

Corn dust is a significantly energetic dust and widely used substance in food processing industries. It not only poses dust hazards like suffocation or lungs related issues to the exposed workers but also is highly combustible under a conducive environment. In this study, the minimum ignition temperature (MIT) of corn dust clouds was evaluated at varying combinations of dispersion pressure and concentration using a Godbert–Greenwald (G–G) furnace. A response surface was generated using design expert as a tool for the application of response surface methodology (RSM). The predicted R2 and adjusted R2 are reasonably in close agreement as the difference is less than 0.2. The predicted surface is found to be in good agreement with the experimental results. However, as this is a preliminary study, the model will be improved in future research.

Turbulent flame propagation in corn dust clouds formed in confined and open spaces

Flame propagation stages in a corn dust cloud in a large room size confinement investigated. The clouds ignited by a weak heat source. The mass of the dust identified to be influenced the flame acceleration. Dust in the clouds burnt rapidly through several fluid dynamic mechanisms. Four types of instabilities contributed to fast flame development. Landau–Darrieus and Kelvin–Helmholtz instabilities increased the flame speed in the initial stages of the fireball. In the intermediate and final stages, corrugated and the wrinkled flame structure originated through Rayleigh–Taylor instabilities. In addition to flow aspects and instabilities, the shock waves also enhanced the flame speed. The shock overpressure measured with a dynamic pressure sensor. These shock waves induced Richtmyer–Meshkov instability in the fireball and developed turbulent flames. Density gradients across the fireball (due to higher temperature gradients) caused perturbations. Further, this gradient increased by the shock waves. The crosswind speed through the confinement windows was slower, therefore it has not enhanced the flame speed. Corn dust dispersed quickly to a wider area by the shock waves, established large dust clouds, and lead to explosions. The maximum surface temperature of the fireball predicted as 1384 K. The preheat zone around the fireball identified by an image processing tool. The turbulence parameters at the fireball obtained from qualitative and quantitative methods and analyzed. The clouds of a small quantity of corn dust lead to the formation of larger fireballs due to higher kinematic viscosity than the energy dissipation rate.

A real-time method for sensing suspended dust concentration from the light extinction coefficient

In powder handling and processing industry, location of dust emission can vary, with the suspended dust concentration assessment requiring installation of an immovable or wired equipment. For increased dust sensing, not limited by location within the facility, a portable suspended dust concentration measuring system is needed. In this study, a new method of sensing suspended dust concentration under daylight environment using the change in light extinction coefficient was developed. The method involves capturing images of the suspended dust cloud and then analyzing the light extinction coefficient. This method mitigated the environmental light scattering and absorption and eliminated the noise from the images obtained through a camera by calibration between two targets. Cornstarch, corn dust, and sawdust were used as test materials in this study. The light extinction coefficient (ε) was found to correlate with the suspended dust concentration, and the ε values depended on the dust properties. Mass extinction coefficient (K) was obtained for cornstarch, saw dust and corn dust, from known suspended dust concentrations using image analysis. The mass extinction coefficient of the three sample materials tested in this study were in the range of 0.03–0.04. This method of using light extinction coefficient can be used for real-time sensing of suspended dust concentration in both open and confined spaces.

Effect of Obstacles on Flame Propagation Characteristics of Corn Starch Dust

ABSTRACT The combustible and explosive characteristics of corn starch dust pose a significant safety risk in its production and processing. To reveal the influence of obstacle opening sizes on the flame propagation characteristics, a self-designed vertical experimental platform of a dust combustion pipeline was implemented. Specifically, the flame temperature and pressure changes in the pipeline were collected by micro-thermocouples and pressure sensors, and dust flame images under different conditions were recorded by a high-speed photography system. The results demonstrate that, after being set in the pipeline, the obstacle destroys the flame structure and causes the flame to exist in a strong turbulent and irregular state. Meanwhile, owing to the blocking of the obstacle, the flame may disappear under certain conditions and brightness is reduced. The obstacles have an incentive effect on the flame temperature, and the obstacle opening size is inversely proportional to the peak temperature of the corn dust flame. With an increasing obstacle opening size, the combustion pressure first increases and then decreases. At an opening size of 50 × 50 mm2, the combustion pressure reaches its highest value. Although the obstacles exert an incentive increase on the combustion pressure wave at large opening sizes, obstacles with a sufficiently small opening size significantly inhibit the pressure wave propagation.

CSB raises alert over combustible dust

The U.S. Chemical Safety & Hazard Investigation Board has begun an informational program directed to industries that potentially have conditions that could lead to a combustible dust explosion. Such conditions could occur in chemical and pharmaceutical manufacturing facilities. The board announced the effort on April 30 in Wisconsin near the scene of a dust accident that killed five workers and injured 14 at a corn-processing facility last year. The explosion destroyed most of the plant. The likely source of combustible dust at the Didion Milling facility in Cambria was corn dust produced during milling, according to information CSB released in Wisconsin. Combustible dust comes from many sources, CSB Chairperson Vanessa Sutherland notes, citing chemical and pharmaceutical manufacturing, metal and plastics fabrication, food production, and more. Dust from organic or inorganic materials can burn given an ignition source, she says. Dust can cause an explosion when it is dispersed in oxygen

Transmission and Suppression of Avian Influenza Virus

The growth of AIV is possible with supply of minerals from aeolian desert dust, as cofactors of enzymes, and thus the blockage of the aeolian desert dusts to the poultry farmhouse is important to suppress the enzymatic activity of AIV. South Georgia of Subantarctic Islands may be the source of Continental AIV, so that Continental AIV can become endemic within the local bird population when surrounding environments are close to Subantarctica of South Georgia. There are food webs in sequence of aquatic virus, bacteria, phytoplankton, zooplankton, krill, fish and squid while penguins feed on the fish or squid infected by mutant virus to generate LPAI after an incubation period. When migratory birds move to the Continents, HPAI can spread in the Continents due to low UV-B radiation, enough feed of rice, wheat, corn, wetland, and mineral-enriched desert dust. The clean room is equipped with air washers to remove aeolian dusts and migratory birds feces from working personnel and equipments, heaters to keep the pasteurisation of ultra-high temperature at 135°C for 1 - 2 seconds to inactivate AIV, humidifier to keep wet state above 65% relative humidity for weak virus activity, and the UV-C lamps (254 nm) to finally inactivate AIV. Since AIV doesn’t like the high salinity and high relative humidity, seawater is blanketed as sprayer to maintain high salinity (>20 ppt) and high relative humidity (>65%) from the top to the bottom of the poultry farmhouses for suppression of AIV transmission from infected aeolian dust coming from outside.

Characterization and cost savings of pellets fabricated from Zea mays waste from corn mills combined with Pinus radiata

In Chile, the demand for pellets has increased considerably in the last years. However, woodchips and sawdust from Pinus radiata which are the traditional materials used for its confection are not always available, making it necessary to investigate other biomass sources complementary.In this study, the residue from corn milling (corn dust) in a maximum distance of 49 km from the pellet production company was analyzed and evaluated as a biomass source. The physical-mechanical and energetic properties of this material were analyzed, then the quality of the pellets created with different percentages of this and P. radiata sawdust was determined.The company requires 10,000 tons of material for its production at a cost of US$80,000 annually. Its distance from the sources of P. radiata sawdust causes it to make them pay US$ 8 t−1 for the material compared to US$ 3 t−1 that companies close to the sources pay, affecting its competitiveness.It was determined that the test tube 50M/50PR meets all the quantitative, qualitative and economic requirements. The acquisition of the 5000 tons required would generate a cost of US$5800 in transporting this material to the plant, this way the company would save US$34,200 in its operational costs annually.

Aflatoxin B1 Contamination of Dairy Feeds after Storage in Farm Practice in Tropical Environmen.

The objective of this study was to determine the contamination of aflatoxin B1 (AF-B1) when keeping various dairy feeds in a farm environment. The study was carried out from March to May 2011 and involved 63 small holder dairy farms belonging to a single dairy cooperative in Chiang Mai province, Thailand. All feed samples used for milking cows including 4 commercial concentrates (CC1 to CC4), by-products from local corn processing factories fermented in plastic bags (SIL), and corn and cob meal or corn dust (CCD). Feed samples were collected 2 times at before and after storage. Farmers were requested to store CC1 to CC4 and CCD for a month and SIL for a week using their routine on-farm storage arrangements. All samples were measured for their AF-B1 concentrations by ELISA. Results showed that AF-B1 concentrations of CC1 to CC4, SIL and CCD before storage were 5.1, 4.1, 4.0, 4.2, 5.5 and 5.5 μg/kg, respectively, and after storage the concentration of AF-B1 were 9.7, 6.5, 9.8, 12.3, 11.4 and 20.0 μg/kg, respectively. CCD at after storage was the only feed that had mean level more than 20 μg/kg. Concentrations of AF- B1 at before storage in all feeds were significantly lower than after storage (P<0.01), and the increased ratio of AF-B1 levels was approximately 2 to 3 times. The study concluded that increased AF-B1 levels are related to feed types and farm conditions.

Occupational asthma to gel flux containing dodecanedioic acid

Most occupational asthma from electronic solder fluxes is due to colophony (1, 2). We report the first case of occupational asthma to electronic colophony-free gel flux predominantly containing dodecanedioic acid. The patient worked as an electronics instructor from 1999; he initially used solder wire and a separate flux (both colophony). In 2002, he changed to a colophony-free solder wire (predominantly palmitic acid) and a separate gel flux. In 2004, he developed work-related stuffy nose and dyspnoea. This became worse in 2005 when he woke up twice a night and had a blocked nose, wheeze and sputum for the first 2 h after waking. He was worse in the evening after soldering or the night following soldering. He had no asthma, hay fever or eczema in childhood. His father had occupational asthma from corn dust, but his sister had no asthma. He smoked seven to 10 cigarettes per day since age 17 and gave up 6 weeks before being seen in clinic. He had negative skin tests to all common environmental allergens. He completed serial peak expiratory flow (PEF) measurements every 2 h for a total of 4 weeks. When plotted in Oasys (3), the record showed large deteriorations in PEF (declining up to 120 l/min from mean rest PEF) when he visited the soldering bays and intermittent smaller deteriorations when working in the office. The record was scored by the Oasys work effect index (3) as 3.00 (probable occupational asthma; a score of >2.50 has a sensitivity of 75% and specificity of 94%; 3). The area between the curves (ABC) plot (4) in Oasys analysed the two exposures separately and gave an ABC from waking score of 56 l/min/h in the soldering bay and 5 l/min for the office work (an ABC score of ‡15 l/min/h has a sensitivity of 69% and specificity of 100% for occupational asthma diagnosis; 4). His mean work day diurnal variation was 21% and mean rest day diurnal variation was 12%. His exhaled nitric oxide (FENO) level while exposed was 14.3 ppb (Aerocrine Niox at 50 ml/s). He was admitted for specific inhalation challenge testing to both solder wires and fluxes. He melted approximately 5 m of solder wire (using an iron heated to 370 C) spread over three challenges totalling 70 min. For the fluxes, he dipped the soldering iron into the flux approximately every 10 s, letting it fume into the challenge chamber after each insertion. For the colophony flux, he did this over three challenges totalling 17 min and for only 8 min when using the colophony-free gel flux. Figure 1 shows the results of the colophony and dodecanedioic acid fluxes. His forced expiratory volume in 1 s (FEV1) fell by a maximum of 23% from baseline when he was exposed to the dodecanedioic acid flux. He was negative to the colophony wire and wire containing predominantly palmitic acid. His nonspecific reactivity was >4800 lg of methacholine (via the Yan method) prechallenge, becoming measurable postchallenge at 3490 lg. Two years after removal from exposure and while working as an apprenticeship manager without soldering exposure, his asthma continues, but is no longer work-related and his FENO remains normal at 10.7 ppb. Dodecanedioic acid has an asthma hazard index of 0.94 using the chemical asthma hazard assessment programme (5); a value >0.5 has a high probability of being an asthmagen. Other noncolophony based fluxes such as palmitic acid and adipic acid (previously described in a pharmaceutical worker; 6) also have high hazard indexes (0.92 and 0.75 respectively).

Size Distribution and Rate of Dust Generated during Grain Elevator Handling

Dust generated during grain handling can pose a safety and health hazard and is an air pollutant. This study was conducted to characterize the particle size distribution (PSD) of dust generated during handling of wheat and shelled corn in the research elevator of the USDA Grain Marketing and Production Research Center and determine the effects of grain lot, repeated transfer, and grain types on the PSD. Dust samples were collected on glass fiber filters with high volume samplers from the lower and upper ducts upstream of the cyclone dust collectors. A laser diffraction analyzer was used to measure the PSD of the collected dust. For wheat, the size distribution of dust from the upper and lower ducts showed similar trends among grain lots but differed between the two ducts. The percentages of particulate matter (PM)-2.5, PM-4, and PM-10 were 5.19%, 9.81%, and 34.1% of the total wheat dust, respectively. The total dust mass flow rate was 0.94 g/s (equivalent to 64.6 g/t of wheat handled). For shelled corn, the size distributions of the dust samples from the upper and lower ducts also showed similar trends among transfers but differed between the two ducts. The percentages of PM-2.5, PM-4, and PM-10 were 7.45%, 9.98%, and 28.8% of the total shelled corn dust, respectively. The total dust mass flow rate was 2.91 g/s (equivalent to 185.1 g/t of corn handled). Overall, the corn and wheat differed significantly in the size distribution and the rate of total dust generated.

Surfactant-Associated Protein A Provides Critical Immunoprotection in Neonatal Mice

The collectins surfactant-associated protein A (SP-A) and SP-D are components of innate immunity that are present before birth. Both proteins bind pathogens and assist in clearing infection. The significance of SP-A and SP-D as components of the neonatal immune system has not been investigated. To determine the role of SP-A and SP-D in neonatal immunity, wild-type, SP-A null, and SP-D null mice were bred in a bacterium-laden environment (corn dust bedding) or in a semisterile environment (cellulose fiber bedding). When reared in the corn dust bedding, SP-A null pups had significant mortality (P < 0.001) compared to both wild-type and SP-D null pups exposed to the same environment. The mortality of the SP-A null pups was associated with significant gastrointestinal tract pathology but little lung pathology. Moribund SP-A null newborn mice exhibited Bacillus sp. and Enterococcus sp. peritonitis. When the mother or newborn produced SP-A, newborn survival was significantly improved (P < 0.05) compared to the results when there was a complete absence of SP-A in both the mother and the pup. Significant sources of SP-A likely to protect a newborn include the neonatal lung and gastrointestinal tract but not the lactating mammary tissue of the mother. Furthermore, exogenous SP-A delivered by mouth to newborn SP-A null pups with SP-A null mothers improved newborn survival in the corn dust environment. Therefore, a lack of SP-D did not affect newborn survival, while SP-A produced by either the mother or the pup or oral exogenous SP-A significantly reduced newborn mortality associated with environmentally induced infection in SP-A null newborns.

Aspergillus Section Flavi and aflatoxins in dusts generated by agricultural processing facilities in the Philippines

AbstractRelatively few data exist regarding concentrations of aflatoxins and their causative organisms in dusts within occupational environments. Here, we examined Aspergillus Section Flavi populations and aflatoxin levels in 54 samples of dusts generated by agricultural processing facilities as possible indicators of aflatoxin exposure in the Philippines. The average incidence of Aspergillus Section Flavi expressed as a percentage of total mould populations in rice dust, corn dust, feed dust and copra dust were 8, 4, 31 and 10%, respectively. Predominant aflatoxigenic fungi isolated were Aspergillus flavus and A. parasiticus with ratios of 31:1, 40:5, 16:4 and 1:1 in rice dust, corn dust, feed dust and copra dust, respectively. Aflatoxins produced by selected isolates in in vitro rice culture ranged from 100 µg kg−1 to 100.5 mg kg−1. Toxigenicity of isolates based on the average aflatoxin concentrations produced by positive isolates were in the order of copra dust &gt; corn dust &gt; rice dust &gt; feed dust. Average natural concentrations of aflatoxins in rice dust, corn dust, feed dust, and copra dust were 25, 6, 15 and 10 µg kg−1, respectively. Estimates of the amount of inhaled aflatoxins by workers in an 8‐h work shift ranged from 0.06 to 114 ng, the average of which is higher than the amount of aflatoxins ingested by Filipinos due to the consumption of polished rice. The presence of highly toxigenic Aspergillus Section Flavi and aflatoxins in agricultural dust is a critical health risk for workers, considering the frequency of exposure and the possibility of inhalation and subsequent absorption of aflatoxins in the respiratory tract. Copyright © 2006 Society of Chemical Industry

Early exposure to a nonhygienic environment alters pulmonary immunity and allergic responses

The hygiene hypothesis suggests that early life exposure to a nonhygienic environment that contains endotoxin reduces the risk of developing allergic diseases. The mechanisms underlying the hygiene hypothesis are unclear and may involve subtle immune system interactions that occur during maturation. Experimental objectives of this study were to use a novel animal model to test the hygiene hypothesis and to characterize early life immune system responses to a nonhygienic environment. Mice were reared in corn dust, a grain-processing byproduct with a high-endotoxin content and microbial products or in a low-endotoxin environment. The influence of early or later life exposure to corn dust on a subsequent allergen stimulus (ovalbumin) was assessed by bronchoalveolar lavage (BAL) cell analysis, lung histology, serum IgE, and BAL cytokine measurements. The influence of the corn dust environment on the developing pulmonary immune system was assessed by BAL cell analysis and immunostaining of lung tissue. The corn dust environment contained significantly more endotoxin (P < 0.001), and the dust exposures attenuated the cellular inflammatory response to ovalbumin in the adult mouse (P < 0.01) but did not reduce serum IgE levels or alter baseline BAL fluid proinflammatory cytokine levels. The corn dust environment did not induce significant neutrophilia in lavage fluid but significantly increased the number of antigen-presenting cells in alveolar walls early in life by approximately 37%. In conclusion, exposure to a nonhygienic environment did not induce significant airway neutrophilia, yet altered the population of immunologically active cells in the lung and reduced subsequent allergic inflammation.

A Systematic Analysis of the Effect of Corn, Wheat, and Poultry Dusts on Interleukin-8 Production by Human Respiratory Epithelial Cells

The objective of this study was to determine the inflammatory response initiated by various organic dusts by measuring in vitro interleukin-8 (I-8) production from transformed respiratory epithelial cells after dust exposure. To accomplish this objective, the following specific tasks were performed: 1) dust samples were collected from grain farms, grain storage facilities, and poultry houses and their endotoxin levels were determined; 2) A549 transformed respiratory epithelial cells were exposed to 0, 10, 100, or 1,000 μg/ml of organic dust or lipopolysaccharide (LPS); and, 3) production was measured using enzyme-linked immunosorbant assays (ELISAs). The results indicate that LPS induced at all concentrations. All dust types (corn, wheat, and poultry) induced at significantly higher levels than control and at significantly different levels between dust types. Overall there was an increasing trend of elevated production as the concentration of dust exposure was increased except at the highest concentration where IL-8 levels decreased and more cell death was observed. Corn dust exposure induced IL-8 that increased with increasing dust concentration and correlated with increasing amounts of LPS in the corn dust samples. However, IL-8 production in response to wheat dust was inversely related to LPS concentration suggesting that other factors besides LPS are present in the dust that are responsible for induction of IL-8 production. This study indicates that IL-8 induction varies between agricultural dust types and does not always correlate with endotoxin levels present in the dust. Therefore, other factors may be present in the dust that also elicit the immune response after exposure.

Photometer response determination based on aerosol physical characteristics.

Aerosol photometers often are calibrated against field measurements of total or respirable aerosol concentrations. However, the response of these instruments to a particular aerosol concentration level will change if there is a change in aerosol size distribution. To determine a predictable correction factor that relates photometer to gravimetric measurements of an aerosol, the authors performed an analysis of photometer response relative to particle size distribution, density, and refractive index. A series of trials was performed at different concentration levels using both Arizona road dust and ground corn dust. The correction factor was calculated from a knowledge of the instrument response pattern relative to particle size, as well as the ratios of actual dust density and refractive index relative to that of the dust used to calibrate the instruments. Results demonstrated that the calculated correction factors were within 10% of a correction factor predicted from the slope of a linear regression relating gravimetric measurements to the average of photometer readings taken during the sample period.

Total dust, respirable dust, and microflora toxin concentrations in Colorado corn storage facilities.

To aid in the process of characterizing corn dust exposures on farms and in elevators in northeastern Colorado, several parameters were examined. Total dust and respirable dust samples were collected and evaluated. Potentially dangerous dust components evaluated were respirable silica, endotoxin, and mycotoxin levels. Many of the total dust samples (58%) would have exceeded 8-hour time-weighted average (TWA) had sampling been conducted for 8 hours; on farms the operation takes between two and four hours. The same statement may be made for respirable dust samples collected for this project. Nearly 33 percent of the respirable dust samples collected would have exceeded the Occupational Safety and Health Administration (OSHA) TWA had sampling been conducted over an 8-hour period. Respirable silica standards were exceeded at 25 percent of the sampling locations. Presence of mycotoxins at all sites was confirmed by the use of ELISA kits. The most significant finding of this study was high levels of endotoxin at several of the sampling sites. Eighty-five percent of the sampling locations had endotoxin levels above 500 EU/m3. One location, Farm 4, had endotoxin levels of above 1.7 million EU/m3.

IL-10 reduces grain dust-induced airway inflammation and airway hyperreactivity.

To determine whether interleukin-10 (IL-10) could alter the development of grain dust-induced airway disease, we pretreated mice with either saline or IL-10 intravenously, exposed the mice to an inhalation challenge with corn dust extract (CDE), and measured inflammation and the development of airway hyperreactivity. Pretreatment with IL-10, in comparison to saline, reduced the concentration and percentage of polymorphonuclear cells in the lavage fluid 30 min after the inhalation challenge with CDE (P < 0. 05). In comparison to saline-treated mice, IL-10 did not significantly alter the degree of airway hyperreactivity 30 min after the exposure to CDE. IL-10-treated mice lavaged 18 h after challenge with CDE also exhibited a lower percentage of polymorphonuclear cells in the lavage fluid (P < 0.05) and had significantly less airway hyperreactivity than did mice pretreated with the saline placebo (P < 0.05). These findings indicate that exogenous IL-10 is effective in reducing airway inflammation and airway hyperreactivity due to the inhalation of CDE.