Dose-response relationships between occupational aerosol exposures and cross-shift declines of lung function in poultry workers: recommendations for exposure limits

Numerous articles have been published regarding the adverse respiratory health consequences of working in intensive livestock and poultry housing. Threshold limit exposure guidelines are not currently applied to this environment, but they are essential to implement and monitor effective environmental controls. Previous dose-response research work with swine workers has resulted in exposure limit recommendations of 2.5 mg/m3 total dust, 0.23 mg/m3 respirable dust, 100 EU/m3 endotoxin, and 7 ppm ammonia. No similar recommendations have been reported previously for poultry workers. Therefore, an industry-wide study was conducted to examine dose-response relationships of bioaerosol exposures and worker respiratory health. A total of 257 poultry workers were studied for respiratory symptoms, pulmonary function, and exposure to dust (total and respirable), endotoxin (respirable and total), and ammonia. Details of the sampling plan and environmental assessment are described elsewhere. Relationships between exposures and response were studied by correlation and multiple regressions. Significant dose-response relationships were observed between exposures and pulmonary function decrements over a work shift. Exposure concentrations associated with significant pulmonary function decrements were as follows: 2.4 mg/m3 total dust, 0.16 mg/m3 respirable dust, 614 EU/m3 endotoxin, and 12 ppm ammonia.     

Microbial dustiness and particle release of different biofuels

Exposure to organic dust originating from biofuels can cause adverse health effects. In the present study we have assessed the dustiness in terms of microbial components and particles of various biofuels by using a rotating drum as a dust generator. Microbial components from straw, wood chips, wood pellets and wood briquettes were quantified by several methods. Excellent correlations (r >/= 0.85, P < 0.0001) were found: between lipopolysaccharide (LPS) (as determined by 3-hydroxy fatty acid analysis) and endotoxin (as determined by a Limulus test), cultivable bacteria, total number of bacteria and muramic acid; between endotoxin and cultivable bacteria, total number of bacteria and muramic acid; between total number of bacteria and muramic acid; between cultivable fungi and total number of fungi. Straw was dustier than the other biofuels in terms of actinomycetes, bacteria, muramic acid, endotoxin, LPS, particle mass and number of particles. One of the wood chips studied and the straws had comparatively high dustiness in terms of fungi, while both wood pellets and wood briquettes had comparatively low dustiness in terms of all microbial components. An initially high particle generation rate of straw and wood chips decreased over time whereas the particle generation rate of wood briquettes and wood pellets increased during a 5 min rotation period. Particles of non-microbial origin may be the determining factor for the health risk in handling briquettes and pellets. Straw dust contained significantly more microorganisms per particle than did wood chip dust, probably because bacteria were most abundant in straw dust. The concentrations of endotoxin and fungi were high in wood and straw dust; dust from one of the straws contained 3610 EU/mg and dust from one of the chips contained 7.3 x 10(6) fungal spores/mg. An exposure to 3 mg of straw or wood chips dust/m(3) (the Swedish and Danish OEL of unspecific inhalable dust) could cause exposures to endotoxin and fungi higher than levels were health symptoms are seen to develop. The very different levels of dustiness in terms of particles and microbial components of different biofuels shows that dustiness is an important health-relevant factor to consider when choosing among biofuels and when designing worksites for handling of biofuels.     

Assessment of exposure to organic dust in a hemp processing plant

The aim of this preliminary study was to assess exposure to various constituents of the organic dust generated during the processing of hemp in a small group of exposed workers. Airborne levels of inhalable dust, endotoxin and soluble protein, and the respirable, thoracic and inhalable fractions of fungal, bacterial and actinomycete contamination were measured in the personal breathing zone of exposed workers. Inhalable dust, endotoxin, fungal and bacterial contamination all exceeded levels found in similar vegetable fibre processing factories, since inhalable dust levels ranged from 10.4 to 79.8 mg/m(3) and inhalable bacterial levels between 4.7 and 190 x 10(6) cfu/m(3). Soluble protein and endotoxin (r=0.99, P<0.0001), endotoxin and inhalable dust (r=0.94, P<0.005) and inhalable dust and protein (r=0.98, P<0.0001) were significantly correlated, suggesting that there was little variation in the composition of the dust from different sites or activities around the workplace. Andersen sampling gave an indication of background microbe levels, although no attempt was made to identify the specific microorganisms as all plates were significantly overgrown. Airborne assessments demonstrated that exposures were highly task specific. For example, sweeping the floor generated the highest exposure levels of total dust, protein, endotoxin, bacteria and fungi. Therefore, we have shown that a modern-day hemp fibre processing plant produces significant quantities of respirable dust which is highly contaminated with endotoxin and microorganisms. This organic dust has the potential to cause a range of ill health problems.     

Exposure to dust,endotoxin and micro-organisms in the potato processing industry

Exposure to organic dust components was studied in four potato processing plants because preliminary results showed high exposures accompanied by work-related health complaints. Ambient air concentrations of inhalable dust ranged from below 0.4 up to 44 mg m⁻³ [geometric mean (GM) 0.64 mg m⁻³]. Respirable dust concentrations were considerably lower. Personal concentrations of inhalable dust were somewhat higher, and strongly related to a few working tasks dealing with dried starch or protein. Ambient air concentrations of endotoxin ranged from 0.5 to more than 60 000 endotoxin units (EU) per m³ for the inhalable size fraction (GM = 280 EU m⁻³). For the respirable size fraction, endotoxin concentrations were lower (about the same factor as for dust). Personal endotoxin concentrations were lower than ambient air concentrations, probably because workers did not work the whole period of the shift near endotoxin sources. Endotoxin exposure was evaluated as very high; 23% of the workers had a mean exposure above 1000 EU m⁻³ (100 ng m⁻³). Differences between plants had a large influence on both dust and endotoxin exposure. A fairly good correlation was found between counts of airborne gram-negative bacteria and airborne endotoxin of the respirable size fraction. Ambient air levels of bacteria and endotoxin were strongly related to process water temperature, suggesting that exposure reduction can be achieved by lowering this temperature or by other measures that inhibit bacterial growth. We conclude that recycling of process water probably constitutes an exposure source of bacteria and endotoxin in many facilities.     

Occupational exposure to particulate matter and endotoxin for California dairy workers

Occupational exposure of dairy workers to particulate matter (PM) and endotoxin has been considered by some to be of potential concern. This paper reports personal exposure concentrations of PM (μg/m³) and endotoxin (EU/m³) for 226 workers from 13 California dairies. Arithmetic mean personal concentrations for PM_2.5, inhalable PM and endotoxin were 48 μg/m³ (N = 222), 987 μg/m³ (N = 225) and 453 EU/m³ (N = 225), respectively. Using mixed effects models, time spent re-bedding of freestall barns versus any other job conducted on a dairy led to the highest exposure for PM_2.5, inhalable PM, and endotoxin. Personal exposure concentrations were found to be greater than those reported for ambient area based concentrations at the same dairies. A pseudo R-square approach revealed that one area based measure combined with time spent performing tasks explained a significant portion of variation in personal exposure concentrations.     

Effects of personal exposures on pulmonary function and work-related symptoms among sawmill workers

Three green mills and two dry mills were studied for personal exposure to wood dust and biohazards associated with wood dust and their correlation to lung function and work-related symptoms among sawmill workers. The levels of exposure to endotoxin, (1-->3)-beta-D-glucan, bacteria and fungi were high in green mills compared with dry mills. Compared with dry mill workers, green mill workers had significantly high prevalence of regular cough, chronic bronchitis, regular blocked nose, regular sneezing, sinus problems, flu-like symptoms, and eye and throat irritation. Significant positive correlations were found among endotoxin and Gram (-)ve bacteria, (1-->3)-beta-D-glucan and fungi, and endotoxin and (1-->3)-beta-D-glucan exposure levels. Significant dose-response relationships were found for personal exposures and lung function, and lung function and work-related respiratory symptoms. The significant correlations found for respirable fractions show that not only inhalable but also respirable fractions are important in determining potential health effects of exposure to wood dust. The management and employees of the sawmilling industry should be educated on the potential health effects of wood dust. Wood dust should be controlled at the source.     

Exposure to wood dust, resin acids, and volatile organic compounds during production of wood pellets

The main aim of this study was to investigate exposure to airborne substances that are potentially harmful to health during the production of wood pellets, including wood dust, monoterpenes, and resin acids, and as an indicator of diesel exhaust nitrogen dioxide. In addition, area measurements were taken to assess background exposure levels of these substances, volatile organic compounds (VOCs), and carbon monoxide. Measurements were taken at four wood pellet production plants from May 2004 to April 2005. Forty-four workers participated in the study, and a total of 68 personal measurements were taken to determine personal exposure to wood dust (inhalable and total dust), resin acids, monoterpenes, and nitrogen dioxide. In addition, 42 measurements of nitrogen dioxide and 71 measurements of total dust, resin acids, monoterpenes, VOCs, and carbon monoxide were taken to quantify their indoor area concentrations. Personal exposure levels to wood dust were high, and a third of the measured levels of inhalable dust exceeded the Swedish occupational exposure limit (OEL) of 2 mg/m3. Parallel measurements of inhalable and total dust indicated that the former were, on average, 3.2 times higher than the latter. The data indicate that workers at the plants are exposed to significant amounts of the resin acid 7-oxodehydroabietic acid in the air, an observation that has not been recorded previously at wood processing and handling plants. The study also found evidence of exposure to dehydroabietic acid, and exposure levels for resin acids approached 74% of the British OEL for colophony, set at 50 microg/m3. Personal exposure levels to monoterpenes and nitrogen dioxide were low. Area sampling measurements indicated that aldehydes and terpenes were the most abundant VOCs, suggesting that measuring personal exposure to aldehydes might be of interest. Carbon monoxide levels were under the detection limit in all area measurements. High wood dust exposure levels are likely to have implications for worker health; therefore, it is important to reduce exposure to wood dust in this industry.     

Personal exposure to dust, endotoxin and crystalline silica in California agriculture

AIMS: The aim of this study was to measure personal exposure to dust, endotoxin and crystalline silica during various agricultural operations in California over a period of one year. METHODS: Ten farms were randomly selected in Yolo and Solano counties and workers were invited to wear personal sampling equipment to measure inhalable and respirable dust levels during various operations. The samples were analysed for endotoxin using the Limulus Amebocyte Lysate assay and crystalline silica content using X-ray diffraction. In total 142 inhalable samples and 144 respirable samples were collected. RESULTS: The measurements showed considerable difference in exposure levels between various operations, in particular for the inhalable fraction of the dust and the endotoxin. Machine harvesting of tree crops (Geometric mean (GM) = 45.1 mg/m3) and vegetables (GM = 7.9 mg/m3), and cleaning of poultry houses (GM = 6.7 mg/m3) showed the highest inhalable dust levels. Cleaning of poultry houses also showed the highest inhalable endotoxin levels (GM = 1861 EU/m3). Respirable dust levels were generally low, except for machine harvesting of tree crops (GM = 2.8 mg/m3) and vegetables (GM = 0.9 mg/m3). Respirable endotoxin levels were also low. For the inhalable dust fraction, levels were reduced considerably when an enclosed cabin was present. The percentage of crystalline silica was overall higher in the respirable dust samples than the inhalable dust samples. CONCLUSIONS: Considerable differences exist in personal exposure levels to dust, endotoxin and crystalline silica during various agricultural operations in California agriculture with some operations showing very high levels.     

Personal exposures to inorganic and organic dust in manual harvest of California citrus and table grapes

The aim of this study was to determine characteristics of personal exposure to inorganic and organic dust during manual harvest operations of California citrus and table grapes. Personal exposures to inhalable dust and respirable dust were measured five times over a 4-month period of harvesting season. We analyzed components of the dust samples for mineralogy, respirable quartz, endotoxin, and total and culturable microorganisms. Workers manually harvesting were exposed to a complex mixture of inorganic and organic dust. Exposures for citrus harvest had geometric means of 39.7 mg/m(3) for inhalable dust and 1.14 mg/m(3) for respirable dust. These exposures were significantly higher than those for table grape operations and exceeded the threshold limit value for inhalable dust and respirable quartz. Exposures for table grape operations were lower than the threshold limit value, except inhalable dust exposure during leaf pulling. Considered independently, exposures to inhalable dust and respirable quartz in citrus harvest may be high enough to cause respiratory health effects. The degree of vigorous contact with foliage appeared to be a significant determining factor of exposures in manual harvesting.     

棉纺车间空气中可吸尘,内毒素浓度与工人呼吸道反应

本文对338名棉工进行了呼吸道反应调查.并测定了车间空气中粉尘浓度及内毒素浓度.发现前纺车间可吸尘浓度在O.18～1.62m g/m~3,内毒素浓度在94.91～2682.18ng/m~3,棉尘有关症状(包括棉尘病症状和不典型症状)和慢性支气管炎患病率均比对照组高,且与车间粉尘和内毒素浓度呈正相关.与5年前比较,可吸尘或内毒素累积接触量高的男、女工人FEV_1下降均较累积接触量低者明显。     

A triangulation approach to historical exposure assessment for the carbon black industry

The determination of cumulative exposures for individual workers is necessary for research and practice of occupational health and hygiene. Reconstruction of exposures for a study of respiratory morbidity was needed to study the effects of exposure to carbon black production. Approximately 15,800 exposure estimates were needed. There were 22 plants, a 40-year time span, six job categories, and three types of dust-exposure metrics (respirable, inhalable, and "total" dust). Three information sources were used: 1) Industrial hygiene air level measurements where available (several industry-wide surveys had been conducted). 2) A formal process survey identifying specific dates and types of process and control changes. 3) An Historical Relative Exposure Rating Scale; plant health and safety personnel used this spreadsheet-based rating scheme to quantify exposures before and between years of actual measurement relative to a reference year in which measurements were available. A job-exposure matrix was calculated by integrating these three methods. Linear scaling factors were identified to interconvert geometric to arithmetic means and to interconvert total and inhalable dust. Individual worker cumulative exposures were then calculated based upon job histories linked with the job-exposure matrix. The nine-step process for integrating all available relevant data was effective in estimating the exposures for each of the cells of the job-exposure matrix. Among the 1680 workers participating, the mean cumulative inhalable dust exposure was 48.4 mg-years/m3. Early years contribute disproportionately to the cumulative exposures of individuals since levels have declined significantly over time. The use of multiple sources of information, including a relative exposure rating instrument, significantly facilitates reconstruction of historical exposures. Inadequate adjustment for temporal trends can lead to underestimation of cumulative exposures and significantly affect estimation of dose-effect relationships. These methods are applicable to other situations requiring estimation of cumulative exposure with sparse industrial hygiene data in early years.     

Exposure to wood dust and endotoxin in small-scale wood industries in Tanzania

Workers in small-scale wood industries (SSWI) have increased risks of developing asthma and other respiratory diseases. Wood dust and microbial agents have both been suggested to play a role, but few studies have measured endotoxin exposure in SSWI in Africa. We assessed inhalable dust levels in 281 samples from 115 workers and bacterial endotoxins levels in 157 samples from 136 workers from SSWI in Dar es Salaam, Tanzania. The overall geometric mean of personal exposure was 3.3 mg/m(3); geometric standard deviation (GSD) 2.5; range 0.45-67.0 mg/m(3)) and 91 EU/m(3) (GSD 3.7; range 9-4914.8 EU/m(3)) for wood dust and endotoxins, respectively. Dust and endotoxin levels were weakly correlated (r = 0.44, n = 157, P < 0.0001). Between- and within-worker variances and percentages explained by the differences among job titles and seasons were 0.31 (9%) and 0.35 (30%), respectively, for wood dust exposure, and 0.35 (0%) and 0.35 (38%) for endotoxin exposure. Higher dust and endotoxin exposure levels were observed in the dry compared to the wet season, after correcting for differences in exposure between jobs. Carving and manual cleaning were associated with the highest dust exposures. Sewing seat covers and manual cleaning were associated with the highest endotoxin exposures. Dust and endotoxin exposure levels in SSWI are high and appropriate control measures are necessary.     

Respiratory symptoms and occupational exposures in New Zealand plywood mill workers

OBJECTIVES: To study work exposure and respiratory symptoms in New Zealand plywood mill workers. METHODS: Personal inhalable dust (n = 57), bacterial endotoxin (n = 20), abietic acid (n = 20), terpene (n = 20) and formaldehyde (n = 22) measurements were taken and a respiratory health questionnaire was administered to 112 plywood mill workers. RESULTS: Twenty-six percent of the dust exposures exceeded 1 mg/m(3), however, none of the samples exceeded the legal limit of 5 mg/m(3) [geometric mean (GM) = 0.7 mg/m(3), geometric standard deviation (GSD) = 1.9]. Workers in the composer area (where broken sheets are joined together) were significantly (P < 0.01) more highly exposed. Endotoxin levels were low to moderate (GM = 23.0 EU/m(3), GSD = 2.8). Abietic acid levels ranged from 0.3 to 2.4 micro g/m(3) (GM = 0.7 micro g/m(3), GSD = 1.8) and were significantly (P < 0.05) higher for workers in the composer area of the process. Geometric mean levels of alpha-pinene, beta-pinene and Delta(3)-carene were 1.0 (GSD = 2.7), 1.5 (GSD = 2.8) and 0.1 (GSD = 1.4), respectively, and alpha-pinene and beta-pinene levels were significantly (P < 0.001) higher for workers in the 'green end' of the process, up to and including the veneer dryers. Formaldehyde levels ranged from 0.01 to 0.74 mg/m(3) [GM = 0.08 mg/m(3) (= 0.06 p.p.m.), GSD = 3.0]. Asthma symptoms were more common in plywood mill workers (20.5%, n = 112) than in the general population [12.8%, n = 415, adjusted OR (95% CI) = 1.5 (0.9-2.8)]. Asthma symptoms were associated with duration of employment and were reported to lessen or disappear during holidays. No clear association with any of the measured exposures was found, with the exception of formaldehyde, where workers with high exposure reported more asthma symptoms (36.4%) than low exposed workers [7.9%, adjusted OR (95% CI) = 4.3 (0.7-27.7)]. CONCLUSIONS: Plywood mill workers are exposed to inhalable dust, bacterial endotoxin, abietic acid, terpenes and formaldehyde, and they appear to have an increased risk of developing work-related respiratory symptoms. These symptoms may be due to formaldehyde exposure, although a potential causal role for other exposures cannot be excluded.     

Characterization of endotoxin collected on california dairies using personal and area-based sampling methods

Endotoxin, found in the cell wall of gram negative bacteria, is an important contributor to the biological activity of agriculture particulate matter (PM). We analyzed endotoxin in PM collected on 13 California dairies and from the breathing zone of 226 workers during the summer months of 2008. Two particle size fractions were measured: PM(2.5) and inhalable PM. Recombinant factor C assays were used to analyze biologically active endotoxin, while gas chromatography coupled with mass spectrometry in tandem was used to quantify total lipopolysaccharide. Biologically active endotoxin concentrations in the inhalable PM size fraction from area-based samples ranged from 11-2095 EU/m(3) and from 45-2061 EU/m(3) for personal samples. Total endotoxin in the inhalable PM size fraction ranged from 75-10,166 pmol/m(3) for area-based samples and 34-11,689 pmol/m(3) for personal samples. Area-based geometric mean concentrations for biologically active endotoxin and total endotoxin in PM(2.5) and inhalable PM size fractions were 3 EU/m(3), 149 EU/m(3), 60 pmol/m(3), and 515 pmol/m(3), respectively. Personal geometric mean concentrations in the inhalable PM size fraction were 334 EU/m(3), and 1178 pmol/m(3). Biologically active and total endotoxin concentration variation was best explained by meteorological data, wind speed, relative humidity, and dairy waste management practices. Differences in endotoxin concentration and composition were found across locations on the dairy.     

Agricultural seed dust as a potential cause of organic dust toxic syndrome

Aims

Episodes of serious work related health problems resembling organic dust toxic syndrome (ODTS) in workers of a grass seed quality inspection laboratory prompted the authors to study personal endotoxin exposure levels in this facility and in the agricultural seed processing industry. In addition, microbial and inflammatory characteristics of agricultural seeds were studied.

Methods

The authors assessed inhalable dust and endotoxin levels in 101 samples from 57 workers in grass, cereal, and vegetable seed plants who were handling mainly grass seeds as bulk product, and horticulture seeds in smaller quantities. Additionally, real‐time dust exposure was measured using a DataRAM monitor in 12 grass seed workers to obtain more information on exposure patterns during specific tasks. Endotoxin concentrations in seed extracts were determined by LAL assay and seed samples were analysed by scanning electron microscopy. Release of inflammatory cytokines was measured in supernatants of whole blood samples stimulated with lipopolysaccharide (LPS) or agricultural seed extracts in a human whole blood assay (WBA).

Results

Endotoxin concentrations in personal samples were high (geometric mean 1800 EU/m³), particularly in the grass seed quality inspection lab where endotoxin levels up to 274 000 EU/m³ were measured. The recommended health based endotoxin exposure limit of 50 EU/m³ was amply exceeded in almost all personal samples. Job tasks dumping and mixing were associated with highest dust and endotoxin exposures, which was confirmed by real‐time measurements. Microbial infestation was found in almost all seed samples. WBA results showed that most seed extracts were capable of inducing a pronounced dose dependent cytokine release.

Conclusions

Workers handling grass, cereal, or vegetable seeds are at risk of exposure to high levels of endotoxin containing seed dust. Occupational exposure to inhalable agricultural seed dust can induce inflammatory responses, and is a potential cause of ODTS.     

Exposure to grain dust in Great Britain

Airborne grain dust is a complex mixture of fragments of organic material from grain, plus mineral matter from soil, and possible insect, fungal, or bacterial contamination or their toxic products, such as endotoxin. In the 1990s, grain workers in Britain were frequently exposed to inhalable dust >10 mg.m(-3) (8 h), with particularly high exposures being found at terminals where grain was imported or exported and in drying operations (personal exposure typically approximately 20 mg.m(-3)). Since then, the industry has made substantial progress in improving the control of airborne dust through better-designed processes, increased automation, and an improved focus on product quality. We have used information from the published scientific literature and a small survey of industry representatives to estimate current exposure levels. These data suggest that current long-term exposure to inhalable dust for most workers is on average less than approximately 3 mg.m(-3), with perhaps 15-20% of individual personal exposures being >10 mg.m(-3). There are no published data from Britain on short-term exposure during cleaning and other tasks. We have estimated average levels for a range of tasks and judge that the highest levels, for example during some cleaning activities and certain process tasks such as loading and packing, are probably approximately10 mg.m(-3). Endotoxin levels were judged likely to be <10? EU m(-3) throughout the industry provided inhalable dust levels are <10 mg.m(-3). There are no published exposure data on mycotoxin, respirable crystalline silica, and mite contamination but these are not considered to present widespread problems in the British industry. Further research should be carried out to confirm these findings.     

Personal inhalable dust and endotoxin exposure among workers in an integrated textile factory

Abstract

The aim of this study was to determine personal exposure to inhalable dust and endotoxin levels among workers in an integrated cotton-processing textile factory and exposure variability across the different work sections. Full shift measurements were carried out using inhalable conical samplers with 37?mm glass-fiber filters. Personal inhalable dust was determined gravimetrically, and endotoxin levels were analyzed by kinetic chromogenic Limulus Amebocytes Lysate assay. The geometric means of personal dust and endotoxin concentrations were 0.75?mg·m^?3 and 831 EU·m^?3, respectively. The highest dust and endotoxin concentrations were observed in carding section (1.34?mg·m^?3 and 6,381 EU·m^?3, respectively). Altogether, 11% of dust and 89% of endotoxin samples exceeded workplace exposure limits. This study showed a moderate correlation between inhalable dust and endotoxin (r?=?0.450, p?<?0.001). Our findings indicate that low dust exposure does not guarantee a low exposure to endotoxin.     

Inhalation exposure in secondary aluminium smelting

Inhalation exposure at seven UK secondary aluminium smelters was investigated to quantify the main exposures and identify their sources. The substances monitored were gases (carbon monoxide, hydrogen sulphide and nitrogen dioxide), total inhalable dust, metals, ammonia, polycyclic aromatic hydrocarbons (PAHs), particulate fluoride salts and acids. The results showed that people were exposed to a range of workplace air pollutants. Personal exposure results for total inhalable dust were between 700 and 5600 microg x m(-3) and the maximum personal exposure result for particulate fluoride salts was 690 microg x m(-3) (as F). The maximum aluminium, total PAH and lead personal exposure results were 900, 19 and 18 microg x m(-3) respectively. The average proportion of aluminium in total inhalable dust samples was 13% and rotary furnace processes generated the most dust. Particulate fluoride salt exposure was more widespread than hydrofluoric acid exposure. The source of the salt exposure was fluoride containing fluxes. The lead exposure source was lead solder contamination in the furnace charge.