Debunking the Myth of Wool Allergy: Reviewing the Evidence for Immune and Non-immune Cutaneous Reactions

Although wool is commonly believed to cause irritant (non-immune) and hypersensitivity (immune) cutaneous reactions, the evidence basis for this belief and its validity for modern garments have not been critically examined. Publications from the last 100 years, using MEDLINE and Google Scholar, were analysed for evidence that wool causes cutaneous reactions, both immune-mediated (atopic dermatitis exacerbation, contact urticaria, allergic contact dermatitis) and non-immune-mediated (irritant contact dermatitis, itch). Secondary aims of this paper were to examine evidence that lanolin and textile-processing additives (formaldehyde, chromium) cause cutaneous reactions in the context of modern wool-processing techniques. Current evidence does not suggest that wool-fibre is a cutaneous allergen. Furthermore, contact allergy from lanolin, chromium and formaldehyde is highly unlikely with modern wool garments. Cutaneous irritation from wool relates to high fibre diameters (≥ 30-32 µm). Superfine and ultrafine Merino wool do not activate sufficient c-fibres to cause itch, are well tolerated and may benefit eczema management.

Pulmonary function parameters in workers of woolen industry

There is an increase in proportion of workers suffering from occupational diseases. In occupational respiratory diseases, pulmonary function tests are the most important and widely used diagnostic tool. Limited studies have been conducted to evaluate the effect of wool dust on pulmonary function parameters. Hence, the present study was undertaken to evaluate the pulmonary function parameters in workers of woolen industry. This study was done on 150 subjects of either gender who were divided into two groups of 75 each. Group I comprised of healthy subjects who served as controls and group II included workers of woolen industry. The values of lung function parameters i.e. volumes and flow rates in these workers were found to be lower than the healthy controls. The significant reduction in percentage predicted values of FEV1 (82 vs 59), FVC (79 vs 63) and MVV (77 vs 64) in workers as compared to healthy controls indicates obstructive pattern of respiratory abnormality. In male workers, percentage predicted FEV1% was significantly lower. The values of all other parameters were lower in female workers. There was a significant decrease in FEV and FVC with increase in age in group I and this negative correlation was statistically significant. The decrease in respiratory volumes and flow rates was more with increase in duration of exposure to wool dust. It can be concluded that wool dust present in environment of woolen industry affected the pulmonary function parameters of the workers leading to obstructive pattern of respiratory changes.

Toxicological responses in SW mice exposed to inhaled pyrolysates of polymer/tobacco mixtures and blended tobacco

Modern cigarette manufacturing is highly automated and produces millions of cigarettes per day. The potential for small inclusions of non-cigarette materials such as wood, cardboard packaging, plastic, and other materials exists as a result of bulk handling and high-speed processing of tobacco. Many non-tobacco inclusions such as wood, paper, and cardboard would be expected to yield similar pyrolysis products as a burning cigarette. The aircraft industry has developed an extensive literature on the pyrolysis products of plastics, however, that have been reported to yield toxic by-products upon burning, by-products that have been lethal in animals and humans upon acute exposure under some exposure conditions. Some of these smoke constituents have also been reported in cigarette smoke. Five synthetic polymers, nylon 6, acrylonitrile-butadiene-styrene (ABS), nylon 12, nylon 6,6, and acrylonitrile-butadiene (AB), and the natural polymer wool were evaluated by adding them to tobacco at a 3, 10, and 30% inclusion level and then pyrolyzing the mixture. The validated smoke generation and exposure system have been described previously. We used the DIN 53-436 tube furnace and nose-only exposure chamber in combination to conduct exposures in Swiss-Webster mice. Potentially useful biological endpoints for predicting hazards in humans included sensory irritation and pulmonary irritation, respiratory function, clinical signs, body weights, bronchoalveolar lavage (BAL) fluid analysis, carboxyhemoglogin, blood cyanide concentrations, and histopathology of the respiratory tract. Chemical analysis of selected smoke constituents in the test atmosphere was also performed in order to compare the toxicological responses with exposure to the test atmospheres. Under the conditions of these studies, biological responses considered relevant and useful for prediction of effects in humans were found for sensory irritation, body weights, BAL fluid analysis, and histopathology of the nose. There was a marked sensory irritation response that recovered slowly for some polymers. Sustained body weight depression, lesions of the respiratory epithelium of the nose, and morphological changes in pulmonary alveolar macrophages (PAM) were observed after exposure to some polymer/tobacco pyrolysates. These responses were increased compared to exposure to tobacco pyrolysate alone. No moribundity or mortality occurred during the study. The data suggest that polymeric inclusions pose a minimal additional toxicologic hazard in humans.

Calibration Study on Subchronic Inhalation Toxicity of Man-Made Vitreous Fibers in Rats

This 3-mo inhalation study investigated the biological effects of a special-purpose glass microfiber (E-glass microfiber), the stone wool fiber MMVF21, and a new high-temperature application fiber (calcium-magnesium-silicate fiber, CMS) in Wistar rats. Rats were exposed 6 h/day, 5 days/wk for 3 mo to fiber aerosol concentrations of approximately 15, 50, and 150 fibers/ml (fiber length >20 microm) for E-glass microfiber and MMVF21. For the CMS fiber only the highest exposure concentration was used. During a 3-mo postexposure period, recovery effects were studied. In the highest exposure concentration groups, gravimetric concentrations were 17.2 mg/m3 for E-glass microfiber, 37 mg/m3 for MMVF21, and 49.5 mg/m3 for the CMS fiber. After 3 mo of exposure, lung retention of fibers longer than 20 micro m per lung was 17 x 10(6) for E-glass microfiber, 5.7 x 10(6) for MMVF21, and 0.88 x 10(6) for CMS. After 3 mo of recovery the concentration of the long fiber fraction was decreased to 38.4%, 63.9%, and 3.0% compared to original lung burden for the E-glass microfiber, MMVF21, and CMS, respectively. Biological effects measured included inflammatory and proliferative potential, histopathology lesions, and the persistence of these effects over a recovery period of 3 mo. Generally, observed effects were higher for E-glass microfiber when compared to MMVF21. The following clear dose-dependent effects on E-glass microfiber and MMVF21 exposure were observed as main findings of the study: increase in lung weight, in measured biochemical parameters and polymorphonuclear leukocytes (PMN) in the bronchoalveolar lavage fluid (BALF), in cell proliferation (BrdU-response) of terminal bronchiolar epithelium, and in interstitial fibrosis. The values observed in the proliferation assay on the carcinogenic E-glass microfiber indicate that this assay has an important predictive value with regards to potential carcinogenicity. Surprisingly, for the biosoluble CMS fiber, fibrogenic potential was detected in this study. The results of the CMS exposure group indicate that effects may be dominated by the presence of nonfibrous particles and that fibrosis may not be a predictor of carcinogenic activity of fiber samples, if the fiber preparation contains a significant fraction of nonfibrous particles. In summary, this study demonstrates the importance of fiber dust contamination by granular components. For future subchronic studies a longer posttreatment observation period would be advisable.

Lanolin allergy: history, epidemiology, responsible allergens, and management

Allergy to lanolin has been recognized by dermatologists for decades. This review summarizes the history, epidemiology, and allergenicity of lanolin and its derivatives. "The lanolin paradox" and the safety of pharmaceutical-grade lanolin products are also discussed.

Occupational rhinoconjunctivitis and asthma in a wool worker caused by Dermestidae spp

BACKGROUND

The family Dermestidae belongs to the order Coleoptera. Occupational allergy has been described in museum personnel. A 31-year-old male wool worker presenting rhinoconjunctivitis and asthma episodes probably linked to exposure to Dermestidae-infected wool was investigated.

METHODS

Extracts prepared either from insect bodies or from dust from parasitized wool were used for skin prick testing (SPT), conjunctival and bronchial provocation tests and in vitro determinations.

RESULTS

SPT and provocation tests were positive to both extracts. PEFR measurement demonstrated the association between the patient's symptoms and occupational exposure to Dermestidae. Specific IgE to both extracts was detected and immunoblotting revealed several protein bands from 5 to 200 kDa that were reactive to IgE from the patient's serum.

CONCLUSIONS

Dermestidae exposure in wool workers when handling parasitized wool can be a cause of IgE-mediated rhinoconjunctivitis and asthma.

Respiratory symptoms and pulmonary function in a group of women weavers in South Africa

Respiratory symptoms and ventilatory capacity were studied in 97 women carpet weavers in a hand-made carpet weaving industry in Umtata, Transkei, South Africa. The controls were from a bottling plant in the same city. Both groups were Black Africans from the Xhosa-speaking population. The population we studied were non-smokers and there was no significant difference in age, race or height between the groups. The exposed weavers had significantly lower forced expiratory indices than the control group. Mean forced expiratory volume in 1 second (FEV1), forced mid-expiratory flow (FEF 25-75%), forced expiratory flow between 200 ml and 1200 ml of forced vital capacity (FEF 200-1200), and peak expiratory flow (PEF) were: 26.0%, 39.0%, 36.4% and 28.5% lower respectively in the exposed group compared with the controls. Mean forced vital capacity (FVC) and forced expiratory ratio (FEV1/FVC x 100) were 22.0% and 6.6% lower respectively in the exposed group compared with the controls. The percentage predicted (%pred) values of FVC, FEV1, FEV1/FVC ratio, FEF 25-75%, FEF 200-1200, and PEF in the exposed group were 82.9%, 77.1%, 95.6%, 64.6%, 72.2% and 82.8%, respectively. The prevalence of FEV1/FVC ratio less than 70% in the exposed group was 37.2%, while in the controls it was 12%. The exposed group reported a significantly higher prevalence of respiratory symptoms compared to the control. The prevalence of nasal symptoms and cough was 62.8% and 58.1%, respectively in the weavers. Weavers who reported cough, breathlessness, and wheezing had significantly (p < 0.01) lower pulmonary function than those who did not report these symptoms. The present study demonstrates that the continual exposure to dust in weavers in this industry is associated with significantly lower pulmonary function, higher prevalence of respiratory symptoms, and weavers show signs of airway obstruction compared to workers not exposed to this type of dust. Women in the weaving industry have a significant occupationally related respiratory impairment.

Immunological reactions and respiratory function in wool textile workers

Immunological status and respiratory function were studied in a group of 64 wool textile workers (52 women and 12 men). A group of 46 workers not exposed to wool dust served as a control for the respiratory symptoms and immunologic testing. Skin testing was performed with different wool allergens (domestic and Australian) as well as with common allergens. Ventilatory capacity was measured in wool workers on Mondays before and after the work shift. The prevalence of positive skin tests to all allergens was higher in wool than in control workers, although the difference was statistically significant only for washed domestic wool (wool workers: 42.2%; control workers: 19.6%; p < 0.05). Increased serum IgE levels were more frequent in wool (26.6%) than in control workers (3.1%) (p < 0.01). In wool textile workers there was a high prevalence of acute and chronic respiratory symptoms. Significant across-shift reductions in ventilatory capacity tests, as well as abnormal baseline lung function, were recorded in wool textile workers. Individual data demonstrated that many of the wool workers had FEF25 lower than 70% of predicted. In general, the prevalence of symptoms and the lung function abnormalities did not correlate with the results of specific (wool) skin tests. Our data indicate that exposure to wool dust in some workers may be associated with the development of acute and chronic respiratory symptoms and impairment of lung function. Immunologic abnormalities, although frequent in this group, do not appear to be associated with the severity of these changes.

Textile dermatitis: an update. (I). Resins, additives and fibers

Cases of textile-related dermatitis reported in the medical literature after the mid-1980s are reviewed. Part I focuses on cases in which textile resins, fiber additives, or fibers were the causal agent. Studies which provide insight into understanding fabric-induced prickle and itch are included.

Pharmacologic characterization of wool dust extract in isolated guinea pig trachea

Wool mill workers develop respiratory symptoms and lung function abnormalities associated with their work in the textile industry. As in other workplaces, which process organic materials, the dust generated in the manufacture of wool has been implicated as a cause of these respiratory problems. Pharmacologic studies of wool dust extract were performed in vitro on guinea pig tracheal (GPT) segments. A wool dust extract (WDE) was prepared from material collected from a mill previously surveyed. When the standardized WDE solution was added to an organ bath in increments of 10, 30, 100, 300, and 1000 microliters it caused a consistent, dose-dependent constriction of GPT. Pretreatment of guinea pig tracheas, prior to WDE challenge, with atropine (10(-6) M), pyrilamine (10(-6) M), indomethacin (10(-6) M), verapamil (10(-6) M), TMBS (10(-6) M), BW755C (10(-6) M) and LY171883 (10(-6) M) was studied in order to evaluate receptor-dependent and -independent characteristics of WDE-induced constriction. WDE-induced bronchoconstriction was partially inhibited by the antihistamine pyrilamine. Atropine and leukotriene inhibitors (LY171883 and BW755C) were not found to have a significant protective effect on WDE-induced constriction. Both TMBS and verapamil (intra- and extracellular calcium blocking agent) suppressed the effect of wool dust extract in the range tested. These findings suggest that in this model, WDE-induced airway constriction is only partly attributable to common mediators of bronchoconstriction (e.g., histamine). The airway effects of WDE may be modulated by calcium channel blocking agents.

A case-control study of carcinomas of the nose and paranasal sinuses in the woolen textile manufacturing industry

A population-based case-control study was conducted in Biella, which is located in northwestern Italy, to investigate the reported association between sinonasal carcinomas and woolen fabrics production. The study included 33 cases diagnosed during 1976-1988 (14 adenocarcinomas, 11 epidermoid carcinomas, 3 other specified carcinomas, 1 unspecified carcinoma, and 4 cases without histologic confirmation) and 131 controls. No association was found with smoking. As reported previously, excess risks were observed in wood and furniture workers (odds ratio [OR] = 4.4, 95% confidence interval [95% CI] = 1.41-13.4) and in the leather industry (OR = 3.5, 95% CI = 0.6-20.3). Odds ratios in the wood and furniture industry were 22.0 (95% CI = 4.4-124.0) for adenocarcinomas and 0.9 (95% CI = 0.4-8.3) for epidermoid carcinomas. No association was found with the woolen textile or garment industries (OR = 0.8, 95% CI = 0.2-2.8), nor with farming, construction, metal works, and transport. Odds ratios for the textile industry did not vary with length of exposure or histologic type. Power for detecting an odds ratio of 3.0 at the 95% level of significance was 40%.

Respiratory disorders and atopy in cotton, wool, and other textile mill workers in Denmark

A cross-sectional study of respiratory disorders and atopy in Danish textile industry workers was conducted to survey respiratory symptoms throughout the textile industry, to estimate the association of these disorders with atopy, and to study dose-response relationships within the cotton industry. Workers at cotton mills, a wool mill, and a man-made fiber (MMF) mill were examined. Four hundred nine (90%) of the 445 workers participated in this survey, i.e., 253, 62, and 94 workers at the cotton mills, the wool mill, and the MMF mill, respectively. An interview designed to assess the prevalence of common respiratory and allergic symptoms was given to all workers willing to participate, and blood samples were drawn. Lung function measurements determined a baseline FEV1, FVC and the change in FEV1 and FVC during work hours on a Monday. The working environment was examined for dust, bacteria, endotoxins, and molds, and the exposure was estimated for each participant. The mean personal samples of airborne respirable dust and respirable endotoxin were highest in the cotton industry, i.e., 0.17-0.50 mg/m3 and 9.0-126 ng/m3 respectively, whereas mold spores were found in the highest concentrations in the wool mill: 280-791 colony-forming units (cfu)/m3. Only small concentrations of microorganisms were found in the MMF mill. The mean change in FEV1% and FVC% was greatest among atopic individuals in both cotton and wool industry and other textile industries although the differences were not significant. FEV1% and FVC% in the cotton workers were significantly associated with the cumulative exposure to respirable endotoxin. Byssinosis was diagnosed only in the cotton industry. We found a dose-response relationship between endotoxin exposure and byssinosis, and a significant association between A-1-A serum concentrations less than or equal to 35 mumol/liter and byssinosis, a finding we are further evaluating in subsequent studies.

Pulmonary function studies in 15 to 18 years age workers exposed to dust in industry

Pulmonary function tests (VC, FEV1% and FEF25-75%) were evaluated in 15 to 18 years age workers employed in slate pencil industry exposed to silica dust, in wool carpet industry exposed to wool dust and in diamond cutting and polishing exposed to carbon dust. These values were compared with the values obtained in clinically healthy non-smokers of the same age group. The results revealed significant impairment of VC in diamond workers, and FEF25-75% in slate pencil workers. When the values were observed according to smoking habits in diamond workers, VC, FEV1 and FEF25-75% were all significantly reduced in smokers whereas in non-smokers only VC was lowered significantly. Among slate pencil workers FEF25-75% was significantly reduced in both smokers and non-smokers. Wool dust exposed workers showed reduced values than normal subjects. The detailed results including the prevalence of various pulmonary impairments were presented.

Inflammation in the lungs of rats after deposition of dust collected from the air of wool mills: the role of epithelial injury and complement activation

In a previous study assessing respiratory symptoms in individuals employed in wool textile mills in the north of England relations between symptoms of chronic bronchitis, breathlessness and wheeze, and rhinitis and current exposure to airborne mass concentration of dust were shown. As preliminary steps in defining the potential hazard associated with dust from the air of wool mills the ability of inspirable dust, collected from the air of wool textile mills, to cause inflammation when injected into the lungs of rats was determined. Dusts were collected from the beginning of wool processing (opening) in one factory and from the middle (combing) and late (backwinding) stages of the process in two other factories. Ability of the dusts to cause inflammation was assessed by instillation into the lungs of rats followed by bronchoalveolar lavage. All the dusts caused some inflammation which peaked on day 1 and did not persist beyond one week. A distinctive aggregation response of mononuclear cells in the lavage, however, had a different time course, peaking at day 7. An attempt was made to determine how the wool mill dusts caused inflammation and experiments showed that the dusts themselves had no inherent chemotactic activity but that they did have a pronounced ability to generate chemotaxins in serum and so could activate complement in lung fluid. In addition, dust collected from ledges in the mills had the ability to injure epithelial cells in vitro which could also contribute to inflammation. A role for endotoxin in the inflammatory activity of the dusts was not discounted and a leachate of the dust had the ability to cause inflammation when injected into the lungs of rats. Wool mill dust is likely to be a complex mixture of materials and these experiments represent a preliminary approach to understanding the biological activity of the whole unfractionated dust and further studies are in progress to define more accurately the toxic material(s) in the dust.

Respiratory and allergic symptoms in wool textile workers

An epidemiological study of 2153 workers in 15 West Yorkshire wool textile mills was conducted to determine relations between respiratory symptoms and exposure to inspirable wool mill dust. A questionnaire designed to elicit all the common respiratory symptoms was developed and tested, and administered to all workers willing to participate (85%). It was translated and administered in Urdu for the 385 workers from Pakistan whose English was not fluent. Symptoms investigated included cough and phlegm, wheezing and chest tightness, breathlessness and its variability, rhinitis, conjunctivitis, chills, nosebleeds, and chest illnesses. Additional questions were asked, where appropriate, about the times of day, days of the week, seasons, and places that the symptoms were worse or better than normal. An environmental survey was carried out at each mill, which included 629 measurements of inspirable dust, enabling estimates to be made of the airborne concentrations of inspirable dust usually experienced by each member of the workforce under current conditions. Overall symptom prevalences were: persistent cough and phlegm, 9%; wheeze, 31%; breathlessness on walking with others on level ground, 10%; persistent rhinitis, 18%; persistent conjunctivitis, 10%; persistent chills, 2%; ten or more nosebleeds a year, 2%; and three or more chest illnesses in past three years, 5%. After allowing for the effects of age, sex, smoking habit, and ethnic group, cough and phlegm, wheeze, breathlessness, rhinitis, conjunctivitis, and nosebleeds were found to be more frequent in those exposed to higher than to lower concentrations of dust. In some experiencing high concentrations (blenders and carpet yarn backwinders) cough and phlegm, wheeze, rhinitis, and conjunctivitis were related to the years worked in such jobs. Relative risks of each symptom in relation to inspirable dust concentrations were calculated by means of a logistic regression analysis. At concentrations of 10 mg/m3, the current United Kingdom standard for nuisance dusts, the risk of cough and phlegm relative to that of an unexposed worker was 1.37, that of wheeze 1.40, breathlessness 1.48, rhinitis 1.24, and conjunctivitis 1.70. Since some of these symptoms may be associated with functional impairment of the lungs, further studies of selected workers are being carried out to estimate the functional effects of exposure to dust in wool textile mills.

Itching from wool fibres in atopic dermatitis

In 24 girls with atopic dermatitis and a history of irritation to wool, more intense itching was provoked on normal skin on the abdomen by a material with coarse wool fibres (36 microns) than with thinner fibres (20 microns). The probability of the materials causing itching could be predicted by the girls by handling the materials.

Textile fiber dermatitis

The review discusses acute and cumulative irritant, allergic contact dermatitis, contact urticaria, and exacerbation of atopic dermatitis due to the physical and chemical nature of textile fibers.

Chronic vascular reactions to steel coil occlusion devices

Original Gianturco steel coil vascular embolization devices and two modifications were compared for their occlusive effects and for the degree of adverse reaction in the surrounding vessel wall. Modifications consisted of silk or Ivalon replacing the wool strands of the original device. Single coils were placed into the left renal artery of nine mixed breed swine and restudied 3 months later. The bare coils did not occlude the vessels nor lead to significant foreign body reaction. Wool, silk, and Ivalon coils produced prompt and sustained renal artery occlusion. Upon histologic examination of the vessel wall, foreign body and chronic inflammatory reaction was found to be strongest against wool. This reaction was less with silk and markedly diminished with Ivalon. The results indicate that silk and Ivalon coils, while having the same occlusive effect, are preferable to wool coils if less local reaction is desired.

Detection, pathogenesis, and prevention of damage to human granulocytes caused by interaction with nylon wool fiber. Implications for filtration leukapheresis

Granulocytes collected by reversible adhesion to nylon wool fiber (NWF) function relatively well in standard in vitro tests; however, they have an abnormally shortened survival time in the circulation. Assuming that this rapid disappearance represents clearance and that recognition by phagocytes is important for such clearance, we used an autologous in vitro cell:cell recognition assay to determine whether phagocytes can detect cellular changes induced by exposure of normal granulocytes to NWF. Human granulocytes incubated with NWF 1 h at 37 degrees C, eluted with 20% acid citrate dextrose plasma, and washed stimulated the hexose monophosphate shunt activity of normal granulocytes an average of twofold (193+/-40% of controls), indicating a recognition response. NWF-induced granulocyte recognition was not dependent on plasma factors or activated complement components but was dependent on the time that the granulocyte was on the NWF and was maximal by 60 min of exposure. After elution from NWF, granulocytes demonstrated resting glucose oxidation rates only slightly higher than normal; however, during the first 20 min of exposure to NWF, granulocytes increased their rate of (14)CO(2) production from [1-(14)C]glucose three- to five-fold. Therefore, experiments were performed to determine whether toxic oxygen metabolites produced by NWF-adherent cells might contribute to recognition. The results showed that (a) normal granulocytes exposed to NWF in the presence of scavengers of superoxide anion (superoxide dismutase) or free radicals (ascorbate, mannitol, or benzoate) and washed before assay did not stimulate glucose oxidation of indicator granulocytes; and (b) NWF granulocytes prepared from cells unable to generate high levels of toxic oxygen metabolites, i.e. cells prepared anaerobically or from a patient with chronic granulomatous disease, also failed to stimulate indicator granulocytes. Human granulocytes placed in contact with NWF show an oxidative burst and become recognizable to other phagocytes. Free radical scavengers are effective in minimizing this recognition conferred on NWF-procured granulocytes.

Atopic dermatitis: the concept of flare factors

A flare factor is a biologic or environmental factor which induces exacerbation of atopic dermatis. Serosis, sweating, scratchy clothes, allergy, infection, scratching, allergic contact dermatitis, anxiety, and coexisting disease are potential flare factors. Different patients have different flare factors, and individual patients may have different flare factors at each patient visit maximizes chances of eliminating or reducing dermatitis.

Effect of wool dust on respiratory function

A group of 252 workers (176 women and 76 men) employed in two wool mills was studied. The mean age of 36 years; mean exposure, 11 years. All women were nonsmokers, and 47 per cent of the men were regular smokers. Ventilatory function was measured by recording maximal expiratory flow-volume curves and forced expiratory volume in 1 sec on the first working day of the week (Monday) before and after the work shift. On maximal expiratory flow-volume curves the flow rates at 50 per cent of the control vital capacity were read. Workers exposed to wool dust for more than 10 years had a higher prevalence of chronic respiratory symptoms than did those with less than 10 years' exposure, but the difference was not significant. Significant reductions during the work shift were found in maximal expiratory flow rates at 50 per cent of the control vital capapity and 1-sec forced expiratory volume, the first test being considerably more sensitive. Workers exposed to wool dust for more than 10 years had signficantly lower than predicted pre-shift values for maximal expiratory flow rates at 50 per cent of the control vital capapcity. Inhalation of wool dust extract caused a significant decrease of maximal expiratory flow rates at 40 per cent of the control vital capacity on partial expiratory flow-volume curves during the 100 min after exposure. Comparison with the same concentration of cotton dust extract revealed a similar effect during the first 40 min after exposure but a significantly larger effect of the cotton dust extract after 40 min. The data suggest that preventive measures, especially medical supervision, are necessary in wool-processing mills to protect workers sensitive to dust.