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1.  Role of family susceptibility, occupational and family histories and individuals' blood groups in the development of silicosis. 
A previous investigation has shown that family susceptibility and occupational and family histories have a decisive role in the development of byssinosis among workers exposed to flax dust. Results of investigation of silicosis in 814 male workers exposed to silica-bearing dust showed that family susceptibility has an important role in the development of silicosis among examined workers, and workers whose fathers had an occupational history of exposure to silica-bearing dust were more resistant to the development of the disease than those with non-exposed fathers. The degree of consanguinity of parents and individuals' blood groups, also, have a role. Workers with cousin parents were relatively highly susceptible to the development of silicosis as well as workers with blood groups "O" or "AB". It has been concluded that the investigated factors might have a role in the development of other occupational diseases and further investigations are indicated.
PMCID: PMC1008760  PMID: 6255981
2.  Endemic Byssinosis in an Egyptian Village 
Previous epidemiological surveys of flax byssinosis may have underestimated the incidence of permanent pulmonary disability by failing to reach those who have had to leave work. In the present study a representative sample of the inhabitants of a village where flax is processed both in the homes and in small plants was examined for byssinosis. The one in five random sample included a total of 190 male family heads living in the village. Dust exposure was evaluated. The study showed that 48·4% of the sample had byssinosis, and this included 92·5% of those working with flax in their homes and 75% of those working in plants. Permanent disability from byssinosis was present in 2·6% of the total sample and 12·1% of those exposed to dust for more than 20 years, whereas 75·8% of the latter group had symptoms of the earlier grades of byssinosis. It is concluded that prolonged exposure to flax dust did not result in a high incidence of permanent disability, and that is disability is not necessarily an eventual outcome in flax byssinosis. The absence of air pollution in the village may play a role in lowering the probability of workers becoming disabled by byssinosis in spite of the high prevalence of symptoms.
PMCID: PMC1038360  PMID: 14180483
3.  Respiratory response in simultaneous exposure to flax and hemp dust 
Žuškin, E., and Valíc, F. (1973).British Journal of Industrial Medicine,30, 375-380. Respiratory response in simultaneous exposure to flax and hemp dust. The effect of exposure to high concentrations of mixtures of hemp and flax dust was studied in 124 workers in two textile mills (mill A: 65-70% hemp and the rest flax, mean dust concentration 13·9 mg/m3; and mill B: about 35% hemp and the rest flax, mean dust concentration 15·8 mg/m3). A high prevalence of byssinosis was found in both mills (80% in mill B; 46·8% in mill A) after a mean exposure of no more than 13 years. In both mills, byssinotics had a higher prevalence of all chronic respiratory symptoms than non-byssinotics. This difference was more pronounced in mill A. Forty-eight percent of byssinotic women and 43% of byssinotic men had byssinosis of grade 2 or 3. Significant mean acute reductions in FEV1·0 and ˙Vmax 50% VC on Monday were recorded in subjects with and without byssinosis with a significantly larger mean reduction in byssinotics (FEV1·0, P < 0·01; ˙Vmax 50% VC, P < 0·05). ˙Vmax 50% VC proved to be a more sensitive test for detecting acute effects of vegetable dust than FEV1·0. The acute respiratory response of the subjects exposed to similar concentrations of flax and mixtures of two different proportions of flax and hemp dust was found to be equal.
PMCID: PMC1069478  PMID: 4753721
A study of byssinosis and other respiratory symptoms in 2,528 flax workers aged 35 years and over in Northern Ireland is reported. This represented 82·5% of the total available population. Only 3% of workers were not seen because of absence or a refusal to co-operate. Workers were interviewed using a questionnaire based on the Questionnaire on Respiratory Symptoms (Medical Research Council, 1960a) with additional questions relating to respiratory symptoms at work.
Byssinosis was found in workers in all stages of the industry, though its prevalence was highest in flax preparers; wet spinners and wet polishers did not appear to be at serious risk of developing the condition. When the effects of other relevant factors had been allowed for, e.g., age, duration of employment, and smoking habits, differences between the prevalence in the two sexes were found to be very small. The associations between byssinosis and the age of workers and their durations of employment in flax-preparing occupations were complex, and it was thought that a selective discharge of affected workers before the study might, in part at least, explain the absence of marked associations between these variables.
Marked associations were found between both chronic bronchitis and exertional dyspnoea and the type of occupation in the mill. Workers in the early preparing occupations had a considerably higher prevalence of these conditions than expected on a null hypothesis. There were also marked associations between byssinosis and bronchitis, and between byssinosis and dyspnoea. The possible importance of these associations with regard to the aetiology of byssinosis is discussed, and it is suggested that byssinosis represents an acute, specific effect of certain textile dusts on the respiratory system, superimposed on a non-specific chronic bronchitic process.
PMCID: PMC1008212  PMID: 14261704
5.  Dust Diseases in Dundee Textile Workers 
A survey of respiratory symptoms and function was carried out in Dundee among 123 men and women in the jute industry and 242 in the flax industry. The selection of workers was biassed in favour of those working in the dustier departments as judged by eye and those in the older age groups. A group of 72 men in a heavy engineering firm were also selected as controls for comparison.
Chronic bronchitis, as defined by Ogilvie and Newell (1957) was recorded in 27% of those interviewed, whose average age was 49. Byssinosis of various grades was recorded in 30% of all working in flax; of these 35 had cough alone worse on Monday, 34 had other respiratory symptoms worse on Monday and in only four persons did the exacerbation persist longer in the week.
In spite of the occurrence of byssinosis, chronic bronchitis was no more prevalent among flax workers than among the others, the average ventilatory function was no worse, and radiographs of the chest revealed no differences. The characteristic fall in expiratory flow rate during the course of exposure to flax dust on Mondays is similar to that found in cotton workers, and is absent in jute workers and in flax workers not admitting to symptoms of byssinosis.
PMCID: PMC1038081  PMID: 13765497
6.  A Clinical and Environmental Study of Byssinosis in the Lancashire Cotton Industry 
The prevalence of byssinosis was measured in a population of 189 male and 780 female workers employed in three coarse and two fine cotton mills. Ninety-eight per cent. of the male and 96% of the female population were seen.
The workers were graded by their histories as follows:
Grade 0—No symptoms of chest tightness or breathlessness on Mondays
Grade ½—Occasional chest tightness on Mondays, or mild symptoms such as irritation of the respiratory tract on Mondays
Grade 1—Chest tightness and/or breathlessness on Mondays only
Grade 2—Chest tightness and/or breathlessness on Mondays and other days
The dust concentrations to which the workers were exposed were measured with a dust-sampling instrument based on the hexhlet. Altogether 505 working places were sampled. In the card-rooms of the coarse mills 63% of the men and 48% of the women had symptoms of byssinosis. In the card-rooms of the fine mills the corresponding prevalences were 7% for the men, and 6% for the women. Prevalences were low in the spinning-rooms in the coarse mills. The mean dust concentrations in the different rooms ranged from 90 mg./100 m.3 in one section of the card-room in a fine mill, to 440 mg./100 m.3 in one of the card-rooms of the coarse spinning mills. The prevalence of byssinosis in the different rooms was closely related to the overall dustiness (r = 0·93). For the three main constituents of the dust, namely, cellulose, protein, and ash, the prevalence of byssinosis correlated most highly with protein, particularly with the protein in the medium-sized dust particles, i.e., approximately 7 microns to 2 mm.
The symptoms of byssinosis may be caused by something in the plant débris which affects the respiratory tract above the level of the terminal bronchioles. This is the site where the medium-sized dust deposits. The possible importance of the fine dust is discussed.
For routine measurements in industry, it is necessary to have a method of assessing dustiness in which the sampling equipment is simple and assessment rapid. As total dust concentration is relatively easy to measure, and correlates closely with the prevalence of byssinosis, permissible levels of dustiness have been expressed in terms of total dust. On comparing the prevalence of byssinosis among workers with short and long exposures and low and high concentrations (Table 11), it appears that a mill with a concentration of 100 mg./100 m.3 or less would be reasonably safe, but in dusty card-rooms it seems that such levels are not possible to achieve at present. As it is necessary to adopt a realistic target that can be achieved, it is suggested that dust concentrations in cotton mills should be less than 250 mg./100 m.3 and that periodic medical examinations should be adopted to protect susceptible workers who can be advised to leave their dusty environment before they are permanently disabled.
PMCID: PMC1039177  PMID: 14437722
7.  Relationships between dust level and byssinosis and bronchitis in Lancashire cotton mills 
Berry, G., Molyneux, M. K. B., and Tombleson, J. B. L. (1974). British Journal of Industrial Medicine,31, 18-27. Relationships between dust level and byssinosis and bronchitis in Lancashire cotton mills. A prospective survey of workers in 14 cotton and two man-made fibre spinning mills was carried out. A questionnaire on respiratory symptoms was completed at the start of the survey by 1 359 cotton workers and 227 workers in man-made fibre mills and again two years later by about half of these workers. Dust measurements were available for 772 women and 234 men cotton workers.
The prevalence of bronchitis was found to be unrelated to dust level but for women was related to years of exposure. The change in symptoms of bronchitis was unrelated to dust level or to length of exposure. There was, however, an increased prevalence of bronchitis in the cotton mills when compared with the man-made fibre mills, and also over the two-year period a greater proportion of symptom-free workers developed symptoms and a lower proportion of those with symptoms lost their symptoms in the cotton mills than in the man-made fibre mills.
The prevalence of byssinosis was related to smoking habits, the smokers having about 1·4 times as much byssinosis as the non- and ex-smokers after allowing for exposure. Byssinosis was associated with the dust level and years of exposure, more so for the women, and an association between the incidence of new cases over the two years and dust level was also found. After allowing for dust level, years of exposure, and smoking there were still differences between the occupational groups in byssinosis prevalence. Strippers and grinders had the highest prevalence followed by drawframe tenters. Speedframe tenters, card tenters, and comber tenters had similar prevalences and ring spinners the lowest.
PMCID: PMC1009538  PMID: 4821407
8.  Lung function in Lancashire cotton and man made fibre spinning mill operatives. 
OBJECTIVES--This survey was conducted to investigate current lung function levels in operatives working with cotton and man made fibres. Dust concentrations, smoking history, and occupational details were recorded so that factors influencing lung function could be identified. METHODS--A cross sectional study of respiratory symptoms and lung function was made in 1057 textile spinning operatives of white caucasian extraction. This represented 96.9% of the total available working population to be studied. Most (713) worked currently with cotton. The remainder worked with man made fibre. Lung function was assessed by measuring forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Exposure to cotton dust was measured in the work area and personal breathing zones, and retrospective exposure to cotton dust over a working life was estimated with accurate work history and best available hygiene data. RESULTS--3.5% of all operatives had byssinosis, 55 (5.3%) chronic bronchitis, 36 (3.5%) work related persistent cough, 55 (5.3%) non-byssinotic work related chest tightness, and 56 (5.3%) work related wheeze. A total of 212 static work area dust samples (range 0.04-3.23 mg/m3) and 213 personal breathing zone samples (range 0.14-24.95 mg/m3) were collected. Percentage of predicted FEV1 was reduced in current smokers (mean 89.5, 95% confidence interval (95% CI) 88-91) in comparison with non-smokers (93.1, 90.5-94.1) and FVC was reduced in operatives currently working with man made fibre (95.3, 93.8-96.9) in comparison with cotton (97.8, 96.6-99.0). Regression analysis identified smoking (P < 0.01), increasing age (P < 0.01), increasing time worked in the waste room (P < 0.01), and male sex (P < 0.05) as being associated with a lower FEV1 and FVC. Current and retrospective cotton dust exposures did not appear as predictor variables in the regression analysis although in a univariate analysis, FEV1 was reduced in those operatives exposed to high dust concentrations assessed by personal and work area sampling. DISCUSSION--This study has documented loss of lung function in association with exposure to cotton dust. Those operatives with work related symptoms had significantly lower FEV1 and FVC than asymptomatic workers. Although lung function seemed to be affected by high dust exposures when operatives were stratified into high and low exposure groups, regression analysis did not identify current dust concentrations as an independent factor influencing loss. Smoking habit was found to explain most of the measured change in FEV1 and FVC. It is likely that smoking and dust exposure interact to cause loss of lung function in cotton textile workers.
PMCID: PMC1128403  PMID: 8563857
9.  Byssinosis, respiratory symptoms and spirometric lung function tests in Tanzanian sisal workers 
ABSTRACT Byssinosis and other respiratory symptoms and acute and chronic changes in FVC and FEV1·0 were investigated in 77 workers in sisal spinning and 83 workers in sisal brushing departments in six Tanzanian sisal factories. Although the prevalence of byssinosis in spinning departments was found to be low (5·2%), it was very high in brushing departments (48·2%). Workers in brushing were exposed to sisal dust for a significantly longer period (11·77 ± 7·3 years) compared to workers exposed to sisal in spinning (2·85 ± 2·56 years). Although the number of smokers in brushing (42%) was similar to that in spinning (37%), smokers were more prone to byssinosis than were non- or ex-smokers after standardisation for duration of exposure. We were unable to measure dust levels in this study, but dust levels in spinning and brushing are cited from previous studies. These confirm our impression that the dust level in spinning is higher than that in an average cotton carding department and far higher in brushing than in spinning. Acute falls in FVC and FEV1·0 were found during the work shift. The extent of the fall in FEV1·0 correlated well with the severity of byssinosis; 75% of the workers with grade II byssinosis and 33% of those with grade ½ + I were found to have acute falls in FEV1·0 greater than 0·2 litres. However some workers, 10% in spinning and 33% in brushing, who denied symptoms of byssinosis, were also found to have acute falls in FEV1·0. Some workers had slight or severe chronic ventilatory impairment from dust (FEV1·0 less than 80%, or less than 60% of the respective predicted values), and these workers were mostly from the brushing department. The prevalence of chronic cough and chronic bronchitis was found to be negligible in workers in the spinning and in the brushing departments: 9·6% had a chronic cough and 12% had chronic bronchitis. It is concluded that a high prevalence of byssinosis associated with chronic and acute changes in FVC and FEV1·0 occurs in the brushing departments of sisal factories, and that this is related to lengthy exposure, high dust level and smoking.
PMCID: PMC1008365  PMID: 656336
10.  Byssinosis, Chronic Bronchitis, and Ventilatory Capacities in Workers Exposed to Soft Hemp Dust 
A study was made of 93 women and 13 men employed in the spinning department of a factory in Yugoslavia processing soft hemp (Cannabis sativa). There were seven occupational groups, with average concentrations of total airborne hemp dust ranging from 2·9 mg./m.3 to more than 19·5 mg./m.3. Thirtyeight women and 11 men, employed in other departments of the factory with average total dust concentrations below 1·0 mg./m.3, were studied as controls.
In the spinning department 40·6% of the workers had byssinosis and 15·1% had chronic bronchitis (defined as persistent cough and phlegm on most days for as much as three months each year during the last two years). None of the controls suffered from either disease.
After adjustment for age, sitting height, and sex, the F.E.V.0·75 and F.V.C. measured at the beginning of the shift were used to assess the long-term effects of hemp dust on the ventilatory function of the lung. The age-adjusted ratio F.E.V.0·75/F.V.C. was also used. A comparison between the control group and the seven exposed groups showed no meaningful association between ventilatory function and present levels of dust exposure, but byssinotics with chronic bronchitis had a mean age-adjusted F.E.V.0·75/F.V.C. ratio significantly lower than that of workers with neither disease (P<0·05).
Acute effects of hemp dust, measured by the change in F.E.V.0·75 and F.V.C. during the shift, were considerable. There were marked reductions in the mean F.E.V.0·75 and F.V.C. during the shift in all the occupational groups exposed to high concentrations of dust. Byssinotics with chronic bronchitis had a significantly greater mean decrease in F.E.V.0·75 during the shift than the byssinotics without chronic bronchitis, and the workers with neither disease (P<0·02).
There is no doubt that the dust of Cannabis sativa hemp can cause byssinosis and at least temporary impairment of ventilatory function, varying in severity according to the level of dust exposure and the presence of respiratory disease.
PMCID: PMC1008770  PMID: 5663421
11.  A study of rope workers exposed to hemp and flax 
Smith, G. F., Coles, G. V., Schilling, R. S. F., and Walford, Joan (1969).Brit. J. industr. Med.,26, 109-114. A study of rope workers exposed to hemp and flax. Respiratory symptoms and ventilatory capacities were studied in 54 men and 22 women exposed to the mixed dusts of hemp and flax in an English rope factory. The preparers and most of the spinners were exposed on average to concentrations of 1·7 mg./m.3 total dust and 0·5 mg./m.3 fine dust. Those employed on subsequent processes had lower exposures at concentrations of 0·5 mg./m.3 total dust and 0·1 mg./m.3 fine dust.
Six men, all in the high exposure group, had symptoms of byssinosis. After adjustment for age and standing height there was no statistically significant difference in the forced expiratory volume (F.E.V.1·0) between those in high dust concentrations and those in low concentrations; neither was there a significant difference between the ventilatory capacities of men with and without byssinosis.
This study shows that byssinosis is an occupational hazard confined to male workers in this factory. It does not appear to be a very serious problem and will diminish with the increasing use of synthetic materials instead of natural fibres.
PMCID: PMC1008903  PMID: 5780101
The same plan of investigation as was used in a previous study of jute workers (Gandevia and Milne, 1965) has been applied to a survey of 50 workers in the blowroom and carding and spinning area of a Sydney cotton mill. Significant decreases in ventilatory capacity were recorded on Friday, Monday, and the following Thursday, with, on the average, complete `overnight' recovery, as indicated by similar morning values. Slightly, but not significantly, greater differences were observed in seven subjects with mild byssinotic symptoms and in five subjects with an observed productive cough on request. No effect of sex, shift, or history of cough and sputum was demonstrable. By contrast with the jute workers, no influence of smoking habit was apparent. The larger decreases in ventilatory capacity were observed in those with the higher F.E.V.1·0:F.V.C. ratios, whereas the reverse trend was noted in the jute workers. The occurrence of significant large decreases in those employed in the industry for less than a month, in conjunction with other evidence, suggests that a factor of `self-selection' may be operative among cotton employees in this country and may be related to the apparently low prevalence of clinically important byssinosis. Attention is drawn to two different patterns of change of ventilatory capacity over a week in subjects exposed to dusts sometimes associated with symptoms of byssinosis; the relationship of these changes and of chronic bronchitis to the development of clinical byssinosis is discussed.
PMCID: PMC1069382  PMID: 5836570
13.  Respiratory disability in ex-flax workers. 
Acute respiratory effects occur in a high proportion of subjects exposed to textile dusts. The extent to which these lead to permanent respiratory symptoms and loss of lung function is unknown. A survey of random population samples was therefore conducted in ten towns in Northern Ireland in which flax processing had been a major source of employment. The MRC questionnaire on respiratory symptoms was administered and Vitalograph tracings recorded on subjects aged 40 to 74 inclusive. An occupational history was taken at the end of each interview. Lung function in ex-flax workers was slightly lower than in control subjects never exposed to flax dust, but the presence of a positive interaction with age meant that differences were apparent only in the younger subjects. Over about the age of 65 the lung function in the ex-flax workers was comparable with that of the controls and overall the loss was at most about half that due to light smoking (1-14 cigarettes a day). The association between a "dust exposure score" and lung function was inconsistent in the two sexes. In men there was a small decrement with increasing dust exposure. In women there was also a small decrement, but a positive interaction with age meant that the women with the highest dust exposure scores had a lower loss with increasing age than the women with the least dust exposure. There was an excess in symptoms in the ex-flax workers but the size of the excess was greater than would be expected from the lung function results. It is possible that, although the survey was conducted without explicit reference to the flax industry, knowledge throughout Northern Ireland that many flax workers have been awarded compensation on the grounds of respiratory disablement may have led to an increased reporting of symptoms in the ex-flax workers.
PMCID: PMC1007653  PMID: 3707867
14.  HLA antigen frequencies in flax byssinosis patients. 
Not all workers exposed to flax dust contract byssinosis. It is not known what determines susceptibility or insusceptibility. This study is an attempt to establish whether the incidence of histocompatibility antigens is involved in susceptibility to the disease. Forty patients suffering from flax byssinosis were tissue-typed for HLA-A and -B antigens. HLA-B27 was significantly more common in the patients (22.5%) than in the controls (5.5%); P = 0.029 after correction for the number of antigens compared. HLA-A11 was present in twelve patients (30%) compared with 14% in the controls; after correction for the number of comparisons, this is not a statistically significant increase. Because HLA-B27, though significantly more common in flax byssinosis, is not necessary for its occurrence (77.5% of our patients did not have it), it is possible that the increase in the frequency of HLA-B27 is attributable to an association with other genes, perhaps those regulating the immune response or coding for antigens at other HLA loci.
PMCID: PMC1008527  PMID: 465375
Of 2,528 persons aged 35 years and over who were interviewed during a survey of Northern Ireland flax mills, 2,003 (79%) carried out tests of one-second forced expiratory volume (F.E.V.1·0) and forced vital capacity (F.V.C.) which were suitable for analysis. The omission of the remaining 525 workers is discussed in the text.
The object of this paper is to compare each of these two measurements of ventilatory capacity between preparers and non-preparers of flax in this industry.
Many factors, other than job, may influence ventilatory capacity; these include sex, smoking habits, the area of the mill, the type of fibre handled, byssinotic grade, age, and stem height. Within each sex and job, workers were divided into eight basic groups according to whether they did or did not smoke, whether the mill was in a town or rural area, and whether the mill processed only flax or flax plus synthetic fibres. Within each of these basic groups of non-byssinotic non-preparers, regression equations of the typeY = a + b1X1 + b2X2where Y = predicted F.E.V.1·0 or F.V.C. (litres), X1 = age (years), X2 = stem height (cm.), and a, b1 and b2 are constants derived from the data, were calculated for non-byssinotic non-preparers. These equations were used to predict the F.E.V.1·0 and F.V.C. of byssinotic and non-byssinotic preparers in each basic group, for each sex separately. The average predicted ventilatory capacity of preparers was then compared with the corresponding averaged observed ventilatory capacity.
It was found that (1) byssinotic flax preparers had a lower mean F.E.V.1·0 and F.V.C. than did comparable groups of non-byssinotic non-preparers, (2) non-byssinotic preparers had a lower average F.E.V.1·0 than did non-byssinotic non-preparers, (3) there is some evidence that preparers with symptoms of grade I or II byssinosis had a lower F.E.V.1·0 than did preparers with no, or only slight, symptoms of byssinosis (grades 0 and ½ respectively).
PMCID: PMC1008257  PMID: 14278798
16.  Dust exposure in manual flax processing in Egypt. 
Manual flax processing originated in Egypt in 2 000 BC. In the present study a representative sample of the workers involved in this trade, where flax is processed in small workshops or homes, was examined, and their dust exposure was evaluated. The study showed that workers handling and processing flax are exposed to high concentrations of dust; the levels of dust at hackling and combing are considerably higher than at batting and spinning. Byssinosis prevailed in 22-9% of the examined workers, and 18-4% of them had their forced expiratory volume in one second reduced by more than 10% at the end of the first morning work period (4 hours) of the week. Both the rates and the grades of these syndromes increased with duration of exposure. Smoking appeared to be one of the important contributory factors in the production of byssinosis. The relationship between dust concentration and prevalence of byssinosis seems to be curvilinear.
PMCID: PMC1008040  PMID: 1131341
17.  Respiratory symptoms and ventilatory function changes in relation to length of exposure to cotton dust 
Thorax  1972;27(4):454-458.
The prevalence of byssinosis, respiratory symptoms, acute changes of ventilatory capacity over the shift, and chronic changes of ventilatory capacity were studied in two groups of non-smoking female workers exposed to practically identical concentrations of the same type of cotton dust but for very different periods of time (16 and 4 years respectively). The prevalence of non-specific respiratory symptoms increased with the duration of exposure to cotton dust only in the subjects with byssinosis. Exposure to cotton dust caused significant reductions over the shift of the mean FEV1.0, FVC and PEF in all the groups of cotton workers examined. In byssinotics the reduction in ventilatory capacity was considerably greater in subjects with longer than in those with shorter exposure to cotton dust, while in non-byssinotics the response was approximately equal in the two groups. Inhalation of a bronchodilator at the end of the shift restored ventilatory function to its pre-shift values except in byssinotics with a longer duration of exposure to cotton dust. Chronic changes of ventilatory capacity developed only in subjects with a longer exposure to cotton dust and were common in the byssinotics.
PMCID: PMC469950  PMID: 5075615
18.  A population study in cotton ginnery workers in the Sudan 
Khogali, M. (1969).Brit. J. industr. Med.,26, 308-313. A population study in cotton ginnery workers in the Sudan. An epidemiological study in cotton ginneries in the Sudan covered 323 permanently employed ginnery workers, a random sample of 35 seasonal farfara workers, and a control group of 24 members of a fire brigade. All the workers studied were men.
The study showed a prevalence of byssinosis (defined as chest tightness starting on return from the annual holiday and continuing for at least three consecutive days) in 20% of the ginnery workers and in 48·6% of the farfara workers. Workers exposed to dust showed a mean fall in F.E.V.1·0 of -0·10 litre during the shift, while workers not so exposed showed a mean rise of +0·23 litre; this difference was statistically significant. The F.E.V.1·0 was adjusted for age and standing height. The adjusted means of F.E.V.1·0 were significantly lower for workers exposed to dust compared with those in the control group.
The workers with byssinosis showed a statistically significant fall in F.E.V.1·0 when compared with all ginnery workers; and a highly significant fall when compared with cotton workers without chest symptoms. An attempt was made to grade the byssinotics according to the extent of fall in F.E.V.1·0 during the shift.
The concentration of fine dust (< 7 μ) was measured in each work place. There was a statistically significant association between the prevalence of byssinosis and the concentration of fine dust when comparing the ginnery and farfara workers. Also, there was a significant relationship between the mean adjusted F.E.V.1·0, the mean fall in F.E.V.1·0, and the fine dust concentration.
PMCID: PMC1008989  PMID: 5346829
19.  Role of histamine in the aetiology of byssinosis. I Blood histamine concentrations in workers exposed to cotton and flax dusts. 
The formation or the accumulation, or both, of histamine in the lungs may be potentiated by agent(s) present in cotton dust at higher level(s) than in flax dust and negligible in cottonseed dust. It has been suggested that such potentiation may be due to the activation of the ability of the lung to produce histamine and/or produce or recruit mast cells; this may present an acceptable explanation of the mechanism by which the propagation of the chronic effect of the dust proceeds in cotton and flax workers. Histamine accumulated in the lung over the weekend is released on exposure to dust causing the symptoms of byssinosis. The difference in the rate of histamine metabolism relative to the rate of histamine formation in byssinotic subjects leads to a more prolonged histamine accumulation than in symptom free subjects, with the consequent appearance of the symptoms of byssinosis. Continuous exposure to dust, without weekend interruption, leads to equivalent rates of histamine formation and metabolism with non-considerable histamine accumulation in the lungs and consequent absence of the symptoms of byssinosis.
PMCID: PMC1009284  PMID: 6202313
20.  Low prevalence of byssinotic symptoms in 12 flax scutching mills in Normandy, France. 
The concentrations of airborne dust and bacteria were determined in 12 flax scutching mills and in two milk processing plants in Normandy, France. A total of 308 of 340 flax workers and 111 of 113 milk processors volunteered to answer a respiratory questionnaire. Personal exposure to airborne dust in the scutching mills varied from 22.2 mg/m3 to 144 mg/m3 and areal concentrations from 8.92 mg/m3 to 47.1 mg/m3. The concentration of Gram negative bacteria ranged from 3970 (colony forming units) cfu/m3 to 67,900 cfu/m3 and that of total bacteria from 12,900 cfu/m3 to more than 600,000 cfu/m3. In all, 20% of the flax scutchers were found, on the basis of the questionnaire, to suffer from persistent cough and 25% from chronic phlegm production. The corresponding figures among milk processors were 3.6% and 4.5%. Unexpectedly, only 12.5% of the scutchers appeared to suffer from byssinotic symptoms even though they were heavily exposed to airborne dust and bacteria. The low prevalence of byssinosis might be due to self selection of the workforce or a relatively low concentration of the causative agent despite high airborne contamination.
PMCID: PMC1008003  PMID: 3378012
21.  Byssinosis Prevalence and Flax Processing* 
Previous evidence suggested that byssinosis in flax workers is caused by the inhalation of dust of biologically retted flax. In the present study no cases of byssinosis were found among workers in a flax plant which produces yarn by chemical degumming instead of biological retting. The absence of byssinosis in this plant could not be attributed to differences in the quantities of dust developed as compared with the conventional retting procedure.
These findings support the view that the agent in flax dust which causes symptoms of byssinosis originates during biological retting of flax and is absent from unretted flax. Chemical degumming of flax appears to be superior to biological retting procedures with respect to the health of the workers.
PMCID: PMC1038385  PMID: 14072625
22.  Byssinosis in Guangzhou, China. 
OBJECTIVES--To study the prevalence of byssinosis and other respiratory abnormalities in workers exposed to cotton dust in Guangzhou in two factories that processed purely cotton. METHODS--All the 1320 workers exposed were included. The controls were 1306 workers with no history of occupational dust exposure. Total dust and inhalable dust were measured by Chinese total dust sampler and American vertical elutriator respectively. A World Health Organisation questionnaire was used. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by a Vitalograph spirometer. RESULTS--The median inhalable dust concentrations ranged from 0.41 to 1.51 mg/m3 and median total dust concentrations from 3.04 to 12.32 mg/m3. The prevalence of respiratory abnormalities in the cotton workers were (a) typical Monday symptoms 9.0%; (b) FEV1 fall by > or = 5% after a shift 16.8%; (c) FEV1 fall by > or = 10% after a shift 4.2%; (d) FEV1 < 80% predicted 6.1%; (e) FEV1/FVC < 75% 4.0%; (f) cough or phlegm 18.2%; (g) chronic bronchitis 10.9%; and (h) byssinosis, defined by (a) plus (b) 1.7%. With the exception of (d), most of the prevalences increased with increasing age, duration of exposure, and cumulative inhalable dust exposure. No increasing trends of respiratory abnormalities were found for current total dust, inhalable dust, and cumulative total dust concentrations. Compared with controls, after adjustment for sex and smoking, with the exception of (d), all the pooled relative risks of respiratory abnormalities were raised for cotton exposure. CONCLUSION--It is concluded that cumulative inhalable cotton is likely to be the cause of byssinotic symptoms, acute lung function decrements, cough, or phlegm, and chronic bronchitis.
PMCID: PMC1128206  PMID: 7795743
23.  Long-Term Exposure to Silica Dust and Risk of Total and Cause-Specific Mortality in Chinese Workers: A Cohort Study 
PLoS Medicine  2012;9(4):e1001206.
A retro-prospective cohort study by Weihong Chen and colleagues provides new estimates for the risk of total and cause-specific mortality due to long-term silica dust exposure among Chinese workers.
Human exposure to silica dust is very common in both working and living environments. However, the potential long-term health effects have not been well established across different exposure situations.
Methods and Findings
We studied 74,040 workers who worked at 29 metal mines and pottery factories in China for 1 y or more between January 1, 1960, and December 31, 1974, with follow-up until December 31, 2003 (median follow-up of 33 y). We estimated the cumulative silica dust exposure (CDE) for each worker by linking work history to a job–exposure matrix. We calculated standardized mortality ratios for underlying causes of death based on Chinese national mortality rates. Hazard ratios (HRs) for selected causes of death associated with CDE were estimated using the Cox proportional hazards model. The population attributable risks were estimated based on the prevalence of workers with silica dust exposure and HRs. The number of deaths attributable to silica dust exposure among Chinese workers was then calculated using the population attributable risk and the national mortality rate. We observed 19,516 deaths during 2,306,428 person-years of follow-up. Mortality from all causes was higher among workers exposed to silica dust than among non-exposed workers (993 versus 551 per 100,000 person-years). We observed significant positive exposure–response relationships between CDE (measured in milligrams/cubic meter–years, i.e., the sum of silica dust concentrations multiplied by the years of silica exposure) and mortality from all causes (HR 1.026, 95% confidence interval 1.023–1.029), respiratory diseases (1.069, 1.064–1.074), respiratory tuberculosis (1.065, 1.059–1.071), and cardiovascular disease (1.031, 1.025–1.036). Significantly elevated standardized mortality ratios were observed for all causes (1.06, 95% confidence interval 1.01–1.11), ischemic heart disease (1.65, 1.35–1.99), and pneumoconiosis (11.01, 7.67–14.95) among workers exposed to respirable silica concentrations equal to or lower than 0.1 mg/m3. After adjustment for potential confounders, including smoking, silica dust exposure accounted for 15.2% of all deaths in this study. We estimated that 4.2% of deaths (231,104 cases) among Chinese workers were attributable to silica dust exposure. The limitations of this study included a lack of data on dietary patterns and leisure time physical activity, possible underestimation of silica dust exposure for individuals who worked at the mines/factories before 1950, and a small number of deaths (4.3%) where the cause of death was based on oral reports from relatives.
Long-term silica dust exposure was associated with substantially increased mortality among Chinese workers. The increased risk was observed not only for deaths due to respiratory diseases and lung cancer, but also for deaths due to cardiovascular disease.
Please see later in the article for the Editors' Summary
Editors' Summary
Walk along most sandy beaches and you will be walking on millions of grains of crystalline silica, one of the commonest minerals on earth and a major ingredient in glass and in ceramic glazes. Silica is also used in the manufacture of building materials, in foundry castings, and for sandblasting, and respirable (breathable) crystalline silica particles are produced during quarrying and mining. Unfortunately, silica dust is not innocuous. Several serious diseases are associated with exposure to this dust, including silicosis (a chronic lung disease characterized by scarring and destruction of lung tissue), lung cancer, and pulmonary tuberculosis (a serious lung infection). Moreover, exposure to silica dust increases the risk of death (mortality). Worryingly, recent reports indicate that in the US and Europe, about 1.7 and 3.0 million people, respectively, are occupationally exposed to silica dust, figures that are dwarfed by the more than 23 million workers who are exposed in China. Occupational silica exposure, therefore, represents an important global public health concern.
Why Was This Study Done?
Although the lung-related adverse health effects of exposure to silica dust have been extensively studied, silica-related health effects may not be limited to these diseases. For example, could silica dust particles increase the risk of cardiovascular disease (diseases that affect the heart and circulation)? Other environmental particulates, such as the products of internal combustion engines, are associated with an increased risk of cardiovascular disease, but no one knows if the same is true for silica dust particles. Moreover, although it is clear that high levels of exposure to silica dust are dangerous, little is known about the adverse health effects of lower exposure levels. In this cohort study, the researchers examined the effect of long-term exposure to silica dust on the risk of all cause and cause-specific mortality in a large group (cohort) of Chinese workers.
What Did the Researchers Do and Find?
The researchers estimated the cumulative silica dust exposure for 74,040 workers at 29 metal mines and pottery factories from 1960 to 2003 from individual work histories and more than four million measurements of workplace dust concentrations, and collected health and mortality data for all the workers. Death from all causes was higher among workers exposed to silica dust than among non-exposed workers (993 versus 551 deaths per 100,000 person-years), and there was a positive exposure–response relationship between silica dust exposure and death from all causes, respiratory diseases, respiratory tuberculosis, and cardiovascular disease. For example, the hazard ratio for all cause death was 1.026 for every increase in cumulative silica dust exposure of 1 mg/m3-year; a hazard ratio is the incidence of an event in an exposed group divided by its incidence in an unexposed group. Notably, there was significantly increased mortality from all causes, ischemic heart disease, and silicosis among workers exposed to respirable silica concentrations at or below 0.1 mg/m3, the workplace exposure limit for silica dust set by the US Occupational Safety and Health Administration. For example, the standardized mortality ratio (SMR) for silicosis among people exposed to low levels of silica dust was 11.01; an SMR is the ratio of observed deaths in a cohort to expected deaths calculated from recorded deaths in the general population. Finally, the researchers used their data to estimate that, in 2008, 4.2% of deaths among industrial workers in China (231,104 deaths) were attributable to silica dust exposure.
What Do These Findings Mean?
These findings indicate that long-term silica dust exposure is associated with substantially increased mortality among Chinese workers. They confirm that there is an exposure–response relationship between silica dust exposure and a heightened risk of death from respiratory diseases and lung cancer. That is, the risk of death from these diseases increases as exposure to silica dust increases. In addition, they show a significant relationship between silica dust exposure and death from cardiovascular diseases. Importantly, these findings suggest that even levels of silica dust that are considered safe increase the risk of death. The accuracy of these findings may be affected by the accuracy of the silica dust exposure estimates and/or by confounding (other factors shared by the people exposed to silica such as diet may have affected their risk of death). Nevertheless, these findings highlight the need to tighten regulations on workplace dust control in China and elsewhere.
Additional Information
Please access these websites via the online version of this summary at
The American Lung Association provides information on silicosis
The US Centers for Disease Control and Prevention provides information on silica in the workplace, including links to relevant US National Institute for Occupational Health and Safety publications, and information on silicosis and other pneumoconioses
The US Occupational Safety and Health Administration also has detailed information on occupational exposure to crystalline silica
What does silicosis mean to you is a video provided by the US Mine Safety and Health Administration that includes personal experiences of silicosis; Dont let silica dust you is a video produced by the Association of Occupational and Environmental Clinics that identifies ways to reduce silica dust exposure in the workplace
The MedlinePlus encyclopedia has a page on silicosis (in English and Spanish)
The International Labour Organization provides information on health surveillance for those exposed to respirable crystalline silica
The World Health Organization has published a report about the health effects of crystalline silica and quartz
PMCID: PMC3328438  PMID: 22529751
The prevalence of byssinosis and chronic respiratory symptoms was studied in 117 workers in four Swedish cotton mills. Changes of forced expiratory volume in 0·75 sec. (F.E.V.0·75) during a Monday and a Wednesday were assessed in 64 male workers in four cardrooms in these mills. Dust sampling was performed with weighed millipore filters.
Prevalences of byssinosis as judged from the workers' histories were 68%, 55%, 44%, and 25% in the four mills; the lowest prevalence of 25% was found in a mill spinning both high grade cotton yarn and rayon. Among 67 workers in the mills having a byssinosis prevalence of 68% and 55%, 60% were non-smokers, 70% had chronic cough, and 27% had chronic dyspnoea. The F.E.V.0·75 decreased on Monday in workers who gave a history of Monday dyspnoea, and to a lesser degree, but still significantly, in those who did not.
In spite of marked differences in fine dust (i.e., dust smaller than 2 mm. diameter) concentrations in the four cardrooms, no significant relations between dust content, byssinosis prevalence, and F.E.V.0·75 changes on Monday could be demonstrated.
The prevention and treatment of byssinosis is discussed. Workers at risk should receive a periodical medical examination including at least a spirographical pulmonary function test at intervals of one year or less.
PMCID: PMC1008256  PMID: 14278797
An attempt was made to assess the importance of selective discharge by death or retirement of workers with respiratory symptoms in a flax mill in Northern Ireland.
One hundred and two men who had worked in a flax mill during 1952-62 and who were aged 35 years or more at the time of leaving were followed up. Fourteen of the men had died and 75 were interviewed. The proportion who had dyspnoea on exertion at the time of interview was significantly higher (at P<0·05) in those who had had byssinosis than in those who had not had byssinosis while in the mill, although the proportions with dyspnoea in preparers and nonpreparers did not differ significantly. The proportion who stated that they had left the mill because of exertional dyspnoea of increasing severity was also significantly higher among those who had had byssinosis than among those who had not. Most of the men who had had byssinosis stated that their symptoms had improved after they left the mill, though some thought that work in the mill had permanently affected their chests, and two said that their symptoms had become gradually more severe since discharge. Of the 14 who had died, certificates of the cause of death were traced for 12, in none of which had respiratory disease been entered as a cause of death. In one man who had been a flax preparer, chronic bronchitis had been considered a `significant condition, contributing to the death'.
The study indicates that any estimate of the prevalence of byssinosis based solely on the examination of workers in the mills underestimates the true magnitude of the problem.
PMCID: PMC1008213  PMID: 14261705

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