Contact Eczema Caused by True Teak (Tectona grandis): A Follow-up study of a Previous Epidemiological Investigation, and a Study into the Sensitizing Effect of Various Teak Extracts

A follow-up study of a previous epidemiological investigation in a furniture factory concerning allergic contact eczema caused by true teak (Tectona grandis) clearly shows that a good educational campaign associated with specific and general prophylactic measures are able to control occupational dermatoses. At the first investigation 20·5% of the workers had allergic contact eczema and/or severe itching whereas only 8·3% suffered from the same complaints on re-examination. The different prophylactic measures previously recommended had been taken.

Patch tests with various teak extracts were made on 13 workers sensitized to teak; these showed that lapachol (a derivative of naphthoquinone) is one of the sensitizing agents in teak wood. Furthermore, allergic reactions were obtained in seven of these workers when Jacaranda wood dust containing lapachol was used as the test substance.

     

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.

     

A Study of 104 Cases of Migraine

An inquiry about present or past history of migraine has been made in a factory of 4,700 employees.

The incidence of migraine among the 1,607 who replied to a questionnaire was found to be 4·9% for men and 13·2% for women.

A family history of migraine was found in migraine sufferers six times more frequently than in non-sufferers, and a personal history of travel sickness was found three times more often in sufferers than non-sufferers. It is believed that an association between migraine and travel sickness has not been reported previously.

Migraine was shown to be by no means exclusive to the “intellectual” or “brain-worker” but such people were more often compelled to stop work during an attack than were manual workers.

Treatment taken consisted of analgesics of the aspirin type in 60% of cases and of ergot preparations in 12·5%. The remainder were content to allow the passage of time to terminate their attacks.

     

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.

     

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.

     

A comparative study of respiratory function in female non-smoking cotton and jute workers

Valić, F., and Žuškin, E. (1971).Brit. J. industr. Med.,28, 364-368. A comparative study of respiratory function in female non-smoking cotton and jute workers. To compare the effect of cotton and jute dust, respiratory symptoms were studied and respiratory function measured in 60 cotton and 91 jute non-smoking female workers of similar age distribution, similar length of exposure to dust, and exposed to similar respirable airborne dust concentrations. Cotton workers had a significantly higher prevalence of byssinosis, of persistent cough, and of dyspnoea (P < 0·01) than jute workers. Among cotton workers 28·3% were found to have characteristic symptoms of byssinosis, whereas none was found among jute workers.

Exposure to cotton but also to jute dust caused significant reductions of FEV_1·0, FVC, and PEF (P < 0·01) over the first working shift in the week. Functional grading of jute and cotton dust effects has shown that about 30% of cotton workers had functional grades F1 and F2, while only 13% of jute workers were found in the same grades (F1). It is concluded that cotton dust may be considered more active than jute though the latter cannot be considered inactive.

     

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.

     

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 FEV_1·0 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 FEV_1·0 were found during the work shift. The extent of the fall in FEV_1·0 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 FEV_1·0 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 FEV_1·0. Some workers had slight or severe chronic ventilatory impairment from dust (FEV_1·0 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 FEV_1·0 occurs in the brushing departments of sisal factories, and that this is related to lengthy exposure, high dust level and smoking.     

A Prognostic Study of Occupational Dermatitis Cases in a Chemical Works

An examination has been made of the medical records of a group of white-skinned men, new starters in a works manufacturing dyestuffs and related chemicals. One thousand, four hundred and fifty-two such men started employment in the works in the five years 1955-59; 745 were employed as chemical process workers, 266 as chemical plant maintenance engineering workers, 335 as non-plant engineering workers, and 106 in various miscellaneous jobs. The process and plant engineering workers have considerable contact with chemicals; the non-plant engineering and miscellaneous workers have little or no chemical contact.

The numbers of men having one or more attacks of occupational dermatitis were 92 (12·35%) process workers, 20 (7·52%) plant engineering workers, 16 (4·77%) non-plant engineering workers, and two (1·88%) miscellaneous workers. The first attack of occupational dermatitis usually occurred within 12 months of starting in the works. Of the 130 first attacks of occupational dermatitis, 17 (13·1%) were caused by the mis-use of sodium hypochlorite (which is used as a means of cleaning the skin), 98 (75·2%) by other primary irritants, and 15 (11·6%) by cutaneous sensitizers.

One hundred and thirty men had their first attacks of occupational dermatitis and of these 85 (64·5%) had no recurrence, 32 (24·6%) had one recurrence, seven (5·4%) had two recurrences, three (2·3%) had three recurrences, two (1·5%) had four recurrences, and one (0·8%) had five recurrences. There was no evidence to suggest that the number of recurrences was related to the length of service. The data may be expressed as the number of recurrences per hundred average population of persons who have had an attack of dermatitis for each year after the first attack. In process workers the number of recurrent attacks for the year following the first episode was 37·8/100 average population, falling in the second to sixth years to 13·0 to 16·7/100. The number of men having a recurrence was 31·9/100 average population in the first year, and 5·3 to 7·7/100 in the second to sixth years. No recurrences occurred after the sixth year. In plant engineering workers the number of recurrences was 61·0/100 average population in the first year, and 7·7 and 7·8/100 in the second and third years. The number of men having a recurrence was 40·1/100 in the first year, and 7·7 and 7·8/100 in the second and third years. There were no recurrences after the third year. In non-plant engineers no man had more than one recurrence, so that the number of recurrences and the number of men having a recurrence are the same in each yearly period. The two rates are in the range 10·7 to 14·2/100 average population in the three years following the first episode of dermatitis, and 7·2 and 8·3/100 in the fourth and fifth years. There were no recurrences after the fifth year.

There were no differences in age at the time of the first attack of occupational dermatitis between those who developed a recurrence and those who did not.

In 17 men the first attack of occupational dermatitis was due to hypochlorite and of these three had one or more recurrences. Thirty-six of the 98 men whose first attack was due to other primary irritants had a recurrence, and six of the 15 men whose first attack was due to sensitizers had a recurrence.

A permanent change of work was necessary in 16 cases; all these men were found jobs within the works and none was obliged to accept work at a lower rate of pay. Four men are known to have left because of occupational dermatitis. The case of occupational dermatitis in this works have a generally favourable prognosis.

     

Diurnal Variation in Ventilatory Capacity: An Epidemiological Study of Cotton and other Factory Workers employed on Shift Work

The change in F.E.V._0·75 during a working shift was studied in a random sample of 473 men employed in three cotton mills in The Netherlands working a three-shift system. Results were also obtained for 198 men, not exposed to industrial dust, who were working in a biscuit factory and two textile factories in the same area. The men were seen only during the shift on which they were working at the time of the study.

Men with byssinosis gave a typical picture of the effects of cotton dust on susceptible workers: a generally low F.E.V. with a marked reduction during the shift; –0·16 l. on the early morning shift, and –0·25 l. and –0·33 l. respectively on the afternoon and night shifts.

Men without byssinosis in the card and blow rooms showed mean changes in F.E.V. during the shift similar to those of men working in the spinning room: a slight rise in the early morning shift of +0·02 l. followed by a fall in both afternoon and night shifts in the region of –0·10 litres. This pattern of change was also found among the workers in the non-dusty factories. The rise in the early shift cannot be explained by the clearing of mucus from the air passages; cotton workers without respiratory symptoms and men in the non-dusty factories who did not produce sputum still showed an increase in F.E.V. during the early shift, though less marked than that of men with respiratory symptoms or who produced phlegm.

The evidence suggests that a diurnal variation in lung function exists and should be taken into consideration both in epidemiological studies and when ventilatory capacity tests are used in periodic medical examinations.

     

Lead in human blood and in the environment near a battery factory

Samples of blood, air, dust, soil, vegetation, and tap water were examined between 1973 and 1975 to determine whether a large battery factory (with a smelter) was contributing to lead in the environment and to lead absorption by the local population. Mean blood lead levels in the children of lead workers were about 6 μg/100 ml higher (P<0·001) than in otherwise comparable children. Capillary blood samples in wives of lead workers were 1·7 μg/100 ml higher (P<0·05) than those of otherwise comparable wives, but venous blood samples from the same subjects showed no significant difference. Lead in dust, soil and vegetation, although variable, decreased in concentration with distance from the factory. This relationship with distance from the factory was not however found in blood lead levels. No consistent effect of distance was found with lead in air, but significantly higher concentrations were recorded at downwind than upwind sites. The blood lead results have been analysed to assess the influence of domestic factors of possible relevance—such as, lead pipes, car ownership, age of house, etc. The presence of a lead-worker in the household appears to outweigh these other factors. The findings are consistent with the work of Burrows (1976) who showed that lead workers take lead home. An interlaboratory comparison on lead in blood was carried out. The two laboratories concerned were found to be equally consistent, but there were differences between them and the design of this comparison did not make it possible to say that the results of either were `absolute' values.     

BYSSINOSIS IN CARDROOM WORKERS IN SWEDISH COTTON MILLS

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.

     

Byssinosis among Winders in the Cotton Industry

In a mill spinning coarse cotton the prevalence of byssinosis and other respiratory symptoms, and the F.E.V._1·0, were measured in a group of 29 men and 117 women employed in the winding room. All the men and 95% of the women at risk were included.

Dust concentrations, measured with a modified Hexhlet at various work points in the winding room, ranged from 1·65 to 6·05 mg./m.³ total dust. These concentrations are higher than 1·0 mg./m.³, which is the threshold limit value for cotton dust recommended by the American Conference of Governmental Industrial Hygienists. The mean dust concentration was 3·48 mg./m.³ compared with 2·85 mg./m.³ in the card room of the same mill.

The prevalence of byssinosis was 18·8% among the women and 13·8% among the men. A comparison among the women showed that those with symptoms of byssinosis had, on the average, significantly lower F.E.V.s than women of similar age without such symptoms. Four women and one man with moderately severe symptoms of byssinosis showed evidence of permanent respiratory disability with effort intolerance and a substantial diminution in F.E.V._1·0. Further studies should be carried out in other winding rooms because, if these findings are repeated elsewhere, they would indicate the necessity for medical surveillance, dust control, and extending the compensation scheme to include winding room workers.

     

Millworkers'' Asthma: Allergic Responses to the Grain Weevil (Sitophilus granarius)

Two laboratory workers, who spent a considerable time each day handling grain infested by the grain weevil (Sitophilus granarius), developed allergic responses to this insect varying from rhinitis and pruritus to marked asthma. These findings suggested that weevil protein present in mill dust could result in sensitization in those exposed continuously. A pilot study was therefore undertaken on 75 volunteer millworkers to determine whether such sensitivity existed. A millworker was defined as anyone who worked in a flour mill or mill producing animal feed from mixed cereals, or who worked in grain-storing silos.

Skin testing with weevil, mixed flour extracts, and a control was carried out on all 75 volunteers; 57% had a positive response to the weevil extract and 68% a positive response to the mixed flour extract. In a control group of 100 workers from two engineering firms matched for age and sex, 34% were positive to the weevil extract and 17% to mixed flour.

From the initial 75 millworkers, 15 were selected for further study based on a positive skin response to the weevil and a history of a productive cough and chest tightness and wheezing when exposed to mill dust. The forced expiratory volume in one second (F.E.V._1·0) was measured after control inhalations and after weevil and mixed flour inhalations. Significant reductions of 20% and 15·4% were found in two subjects after inhalation of weevil extract. In one case wheezing and cough developed. The changes in F.E.V._1·0 were reversed after inhalation of a bronchodilator aerosol.

Twenty-five of the control subjects with positive skin responses to the grain weevil were given similar provocation inhalations but none showed any significant change in F.E.V._1·0.

This pilot study suggests that grain weevil sensitivity is an additional factor in millworkers' asthma.

     

Occupational allergic and irritant contact dermatitis in workers exposed to polyurethane foam

Objectives

To evaluate sensitization to chemicals present in work environment after an outbreak of contact dermatitis in workers of vehicle equipment factory, exposed to polyurethane foam, based on 4,4′-diphenylmethane diisocyanate (MDI).

Material and Methods

From among 300 employees, 21 individuals reporting work-related skin and/or respiratory tract symptoms underwent clinical examination, patch testing, skin prick tests, spirometry and MDI sIgE measurement in serum. Patch tests included isocyanates series, selected rubber additives, metals, fragrances, preservatives, and an antiadhesive agent.

Results

Clinical examination revealed current eczema in the area of hands and/or forearms in 10 workers. Positive patch test reactions were found in 10 individuals, the most frequent to diaminodiphenylmethane and 4-phenylenediamine (7 persons). Reactions to an antiadhesive agent were assessed as irritant (5 workers). Except for sensitization to common aeroallergens, no significant abnormalities were found in the remaining tests. Occupational allergic contact dermatitis was diagnosed in 7 workers, irritant contact dermatitis in 10 and coexisiting allergic and irritant contact dermatitis in 3 workers.

Conclusions

In workers manufacturing products from polyurethane foam, attention should be paid to the risk of developing contact dermatitis. Skin problems in our study group were attributable probably to insufficient protection of the skin.     

Nature, structure, and properties of asbestos cement dust

ABSTRACT Total dust samples produced by machining three commercial asbestos-cement products (autoclaved sheet, non-autoclaved sheet, pipe) were examined for their dimensional, surface, and physicochemical characteristics. Microscopic inspection of dust fractions with different settling characteristics in air allowed determination of the simple dimensional features that apply to respirable fibres—that is, the true diameter, length, and aspect ratio and the coil diameter, coil length, and coil aspect ratio. The respirable fraction as a percentage of the total dust varied with the type of machined product: 8·5% for non-autoclaved sheet, 10·5% for autoclaved sheet, and 35% for pipe.

Quantitative x-ray diffraction of different granulometric fractions showed that the asbestos content decreases with fraction size (thus the asbestos content will change with distance from the dust source). Electron microscopic examination of fine dust (aerodynamic diameter < 7 μm) showed that only about 10% of the inspected particles were optically virgin. From these observations it has been calculated that the threshold limit value of 2 fibres per cm³ of air corresponds to a total dust concentration of 1·2, 0·6, and 0·1 mg/m³ and to a maximum admissible respirable dust content of 0·1, 0·06, and 0·04 mg/m³ for non-autoclaved sheet, autoclaved sheet, and pipe respectively. The surface of optically virgin fibres may still be contaminated by calcium containing particles, as shown by analytical transmission and scanning electron microscope. Dust from the autoclaved product contains fewer calcium coated fibres. The physicochemical behaviour of dust, as shown by dissolution kinetics and absorption of carcinogens from tobacco smoke, is comparable to the behaviour of cement rather than of pure asbestos. In general, asbestos cement dust differs consistently from pure asbestos. Conclusions, drawn from studies on pure asbestos, cannot be applied as such to asbestos cement dust.

     

Reactions to tetanus toxoid

In a factory population the occurrence of reactions to tetanus toxoid was recorded after 6740 injections. The incidence of general reactions was 0·3% and of local reactions 2·6%. The local reaction rate to the first injection of the basic immunization course was 0·9%, to the second injection 2·7%, and to the third injection 7·4%. To booster injections the rate was 1·6%. The local reaction rate was appreciably higher in women than in men — 14·4% and 5·7% respectively in the case of the third injection — and the incidence among women increased with age.     

A neurological and biochemical study of early lead poisoning

ABSTRACT Changes in nerve conduction velocity were found in 94 workers exposed to lead in a battery factory compared with 94 age-matched controls. There was no clinical evidence of nerve damage in the lead workers. The mean blood lead concentration in the 94 lead workers was 2·9 μmol/l (60 μg/100 ml) and their length of exposure to lead ranged from 6 months to 33 years.

All mean maximum motor nerve conduction velocities (MMCV) measured were highly statistically significantly lower in the lead-exposed group when compared with their age-matched controls. Thus mean ulnar MMCV was 53·4 m/s in lead workers and 55·6 m/s in control subjects (p < 0·0005); mean median MMCV was 55·9 m/s in lead workers and 57·3 m/s in control subjects (p < 0·01); mean radial MMCV was 63·9 m/s in lead workers and 71·1 m/s in control subjects (p < 0·0005); mean peroneal MMCV was 46·1 m/s in lead workers and 47·6 m/s in control subjects (p < 0·005).

The amplitude of the muscle action potential produced by proximal stimulation of a nerve was expressed as a percentage of the amplitude of the muscle action potential produced by distal stimulation and the percentage amplitude thus obtained used as an indicator of the conduction velocity of slower fibres (SFCV). Peroneal nerve percentage amplitude of lead workers was statistically significantly lower (p < 0·005) than in the control group (means 86·6% and 90·3% respectively). There were, however, no significant differences in the percentage amplitude in the ulnar and median nerves. It is suggested that percentage amplitude is an inappropriate indicator of SFCV in ulnar and median nerves.

There was no statistically significant correlation to indicate that progressive slowing of nerve conduction (MMCV and SFCV) was associated with increasing exposure to lead (as indicated by blood and urine lead concentrations) or with the commonly measured biochemical changes associated with disturbed haemopoiesis in lead exposure (δ-aminolaevulinic acid dehydrase; free erythrocytc protoporphyrin; haemoglobin and urinary δ-aminolaevulinic acid). MMCV of the ulnar nerve was the only conduction velocity statistically significantly correlated with length of exposure to lead. Increased length of exposure to lead was associated with a decrease in the ulnar MMCV.

Only 13 of the subjects had been exposed to lead for two years or less and in none of them had the blood lead ever risen above 3·9 μmol/l (80 μg/100 ml) in three-monthly tests (mean blood lead concentration at time of testing: 2·8 μmol/l). In these subjects the MMCV of ulnar, radial, and peroneal nerves and the peroneal percentage amplitude were statistically significantly reduced. The results from this group suggest that the onset of nerve conduction changes occurs within two years and at concentrations of lead in blood of less than 3·9 μmol/l (80 μg/100 ml).

     

Effects of different vegetable dust exposures

Valić, F., and Žuškin, E. (1972).Brit. J. industr. Med.,29, 293-297. Effects of different vegetable dust exposures. In order to establish the rank of biological activity of vegetable dusts, five groups of non-smoking female workers exposed to similar concentrations of hemp, flax, cotton, sisal, and jute airborne dust, respectively, were compared as to the prevalence of byssinosis, chronic respiratory symptoms, and one-second expiratory volume changes over the Monday shift. The groups were selected in such a way as to differ in the distribution of age and length of exposure to the respective dust as little as possible.

The prevalence of byssinosis in hemp and flax workers was approximately equal (44% and 43% respectively), in cotton workers it was considerably lower (27%), while no byssinosis was caused by either sisal or jute dust. The highest prevalence of other chronic respiratory symptoms was recorded in hemp workers (39%), followed by flax (36%) and cotton workers (27%), while in sisal (13%) and jute workers (13%) it was the lowest.

Significant mean FEV_1·0 reductions over the shift were recorded in all the groups of textile workers with the largest reductions in hemp workers (19%) followed by flax (11%), cotton (8%), sisal (7%), and jute workers (5%). The application of orciprenaline before the shift diminished the mean acute FEV_1·0 falls over the work shift in all the groups studied.

     

Pneumoconiosis in Makers of Artificial Grinding Wheels, Including a Case of Caplan''s Syndrome

Mass miniature radiography surveys in a factory producing artificial grinding wheels detected cases of pneumoconiosis, mostly of the silicotic type. All cases were traced to the department where the so-called “bond” is prepared and mixed with the abrasive grains of carborundum and artificial corundum. This ceramic-vitrified bond, similar in composition to English general earthenware, contained until recently a significant proportion of free silica.

The miniature film survey was followed up by an investigation on full-sized films, in which 92% of all workers in the bond department participated. The radiographs were subjected to dual independent viewing and it was found that 66% of the men who had worked in the bond department for more than 10 years showed radiological evidence of pneumoconiosis with a high proportion of progressive massive fibrosis (P.M.F.)

Recently the amount of free silica in the ceramic bond has been reduced by the introduction of “frits” in place of powdered flint and part of the factory has been rebuilt and new methods of dust suppression and dust extraction have been introduced. One of the cases presented with the rheumatoid-pneumoconiotic syndrome, first described by Caplan.

It is suggested that some of the cases of pneumoconiosis, attributed to carborundum, may be due to the binding materials of artificial grinding wheels.