Factors associated with massive fibrosis in silicosis

Data on 1432 patients with silicosis on a register in Hong Kong were analysed to examine the association of massive fibrosis with possible predisposing factors. Detailed occupational and clinical histories, clinical records, radiographic readings according to the International Standard Classification of Radiographs of Pneumoconioses, and environmental dust measurements from hygiene surveys were used to obtain information for several variables--namely, age at first exposure, relative dust exposure level, duration of exposure, smoking, previous recorded history of tuberculosis, and background profusion of small opacities. The most significant risk factors associated with massive fibrosis were high relative dust exposure level, a history of tuberculosis, and increased background profusion of small opacities.

Pulmonary effects of polyvinyl chloride dust exposure on compounding workers

Spirometry, chest radiography, environmental measurements, and a questionnaire on respiratory symptoms were used to evaluate the effects of exposure to polyvinyl chloride (PVC) dust on 171 Chinese and Malay PVC compounding workers in comparison with an unexposed reference group. Workers with high cumulative PVC dust exposure had a lower forced expiratory volume in 1 s and forced vital capacity, and a higher prevalence of radiological profusion of small opacities. Wheezing or chest tightness was also significantly more frequent in this group. Unlike previous studies, the PVC compounding workers in this study were exposed to only negligible amounts, if any, of vinyl chloride monomer or thermal degradation products of PVC such as hydrogen chloride, phosgene, or chlorine. The conclusion was drawn that a low grade of pneumoconiosis and a small degree of lung function impairment is associated with PVC dust exposure. Reversible airways obstruction is also likely and warrants further investigation.

Neurobehavioural effects of industrial mixed solvent exposure in Chinese printing and paint workers

Neurobehavioural symptoms and performance tests were evaluated in a group of 78 workers exposed to mixed organic solvents (printers, paint sprayers and paint production workers) and a referent group of 145 unexposed subjects (nonproduction factory workers and volunteer postal workers). Both groups were administered a structured symptoms questionnaire and eight neurobehavioural tests for psycho-motor function, visual and auditory memory. An excess of symptoms of fatigue, irritability, depression, poor memory, sleep disturbances and symptoms suggestive of autonomic dysfunction was found in the exposed group. Neurobehavioural test performance was generally worse, and performance on tests of psycho-motor function (choice reaction test and digit symbol) and auditory memory (digit span and associate learning) was significantly poorer in the exposed group. The findings support the view that apparently healthy and actively employed workers exposed to mixed solvents show neurobehavioural deficits.

Derivation of flow-volume and time domain spirometric indices by digitisation of volume-time spirograms

All the information regarding the forced expiratory manoeuvre are contained in the simple volume-time spirogram. Flow-volume and time-domain indices could be derived by digitising the volume-time spirogram. This paper describes an electronic means of digitising the spirogram and demonstrates its capability in deriving flow-volume and time-domain spirometric indices. The spirograms of 118 granite quarry workers were digitised using an electronic digitising pen. The volume and time data are stored in a micro-computer and a programme written in dBASEIII Plus is used to smoothen and derive the standard volume-time, flow-volume and time domain indices. There was good agreement between digitised and hand-read values (intraclass correlation coefficients, rI, greater than 0.9) for the forced expiratory flow in one second (FEV1) and forced vital capacity (FVC) irrespective of the pulmonary status. There was a small but statistically significant difference between digitised and hand-read FEV1 for those with normal and restrictive pulmonary function groups (-115 ml/sec and 19 ml/sec respectively). There was however, no evidence of systematic bias between the two methods. The technique described herein provides a rapid and accurate means for deriving flow-volume and time domain indices from a volume-time spirogram. It also provides the opportunity to reanalyse previously collected volume-time spirograms and allow for the assessment of small airways function of these subjects using newer flow-volume and time domain indices.

Mortality of a cohort of men in a silicosis register: further evidence of an association with lung cancer

Lung cancer mortality from 1980 to 1986 was studied in a cohort of 1,419 men in a silicosis register who had no previous exposure to asbestos and polyaromatic hydrocarbons. The 28 deaths from lung cancer were statistically in excess of expected (SMR 2.03; 95% CI 1.35-2.93). Excess risks of lung cancer were found in both underground workers (SMR 3.41; 95% CI 1.10-7.97; based on 5 deaths) and surface workers (SMR 1.87, 95% CI 1.18-2.81; based on 23 deaths). All lung cancer deaths were smokers. There was an increase in SMRs with longer latency periods and years of exposure, with the greatest risk found in those who had worked for 30 or more years after more than 30 years since first exposed (SMR 3.07, based on 16 deaths). The risk for lung cancer was higher in those with tuberculosis (SMR 2.52; 95% CI 1.52-3.94) and showed an increasing trend with severity of silicosis, from category 1 to 3 and from category A to C, with highest risk in those with tuberculosis and category 3 (SMR 4.44 based on 3 deaths) or tuberculosis and category C (SMR 7.63 based on 7 deaths). Most of the excess lung cancer risk in silicotics is due to smoking, but a synergistic effect between smoking and silica/silicosis on the risk of lung cancer is also likely. In particular, a possible role of silicosis and tuberculosis as the fibrotic seedbed for malignant growth in the lung is strongly supported.

Urinary levels of proteins and metabolites in workers exposed to toluene. A cross-sectional study

We measured urinary excretion of albumin and retinol-binding proteins to investigate the occurrence of early renal dysfunction in 45 paint workers exposed principally to toluene, and in the same number of unexposed control subjects matched individually for sex and age. Two biological indicators of personal toluene absorption, namely urine hippuric acid and o-cresol, were also measured in the exposed subjects. A significantly higher level and increased prevalence of elevated retinol-binding protein in the urine of exposed workers was found, whereas no significant difference in urinary albumin concentration was seen between the two groups. Urinary concentrations of retinol-binding protein was correlated (r = 0.399, P less than 0.006) with that of o-cresol, but not with hippuric acid or employment duration. The results suggest a dose-dependent early tubular effect due to toluene exposure that might be useful for monitoring individuals exposed to toluene at work.

Fasting urinary hydroxyproline: creatinine ratios in silicosis

Fasting urinary hydroxyproline: creatinine (HOP:C) ratios were measured in 74 patients with suspected (borderline) silicosis (10), simple silicosis (46) and complicated silicosis (9 silicotuberculosis, 4 massive fibrosis, and 5 combined silicotuberculosis and massive fibrosis) and in 18 healthy subjects (controls). There was no statistically significant difference in urinary HOP:C ratios between control subjects (mean 13.8, SD 3.6) and suspected silicotics (mean 18.0, SD 7.6); however, urinary HOP:C ratios were significantly higher in both simple silicosis (mean 25.0, SD 9.9, p less than 0.001) and complicated silicosis (silicotuberculosis and progressive massive fibrosis) (mean 28.6, SD 11.3; p less than 0.001). Urinary HOP:C ratios appeared to show a graduated increase to their highest levels in category 2 silicosis and thereafter remained constant or declined slightly in category 3 silicosis and massive fibrosis. The results support the suggestion that urinary hydroxyproline might be useful as an indicator of disease progression in established silicosis. However, further longitudinal studies are needed to confirm its predictive value.

Occupational mortality in Hong Kong, 1979-1983

Occupational mortality among Hong Kong males aged 15 and above were examined for the period 1979-1983, using routine death registration and census data. Age-standardized mortality ratios (SMR) and relative SMR (RSMR) were calculated for each two-digit occupational group and elevated mortality from all and various causes were highlighted. Mortality from ischaemic heart disease was strikingly associated with professional and sales-managerial occupations whereas colorectal cancers were associated with predominantly clerical and sales workers. Mortality from cancer of the buccal cavity and pharynx was elevated in fishermen as well as in farmers, food, drink and tobacco workers, mechanical fitters, and others. Excesses of liver cancer were found in doctors, fishermen and construction workers. Lung cancer deaths were particularly excessive among fishermen, plumbers and welders, construction workers and transport equipment operators. Fishermen were at high risk of death from cancers of the buccal cavity and pharynx, stomach, liver and lung, cerebrovascular diseases and cirrhosis. Miners and quarrymen experienced high mortality from pulmonary tuberculosis and chronic obstructive airways disease whereas construction workers also experienced high mortality from pulmonary tuberculosis as well as cancers of the liver, lung and bladder and non-Hodgkin's lymphomas. Transport workers were at high risk of dying from cancers of the stomach and lung, cerebrovascular diseases and diabetes mellitus. These and other associations were generally in line with those found from other similar surveys or detailed studies. The limitations of such studies are many and discussed in the context of Hong Kong.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiological progression and lung function in silicosis: a ten year follow up study

Chest radiographs and spirometric tests were performed on 81 patients who had silicosis from two granite quarries in 1975, 73 of whom were followed up for two to 10 (mean 7.2) years. Each patient's initial and most recent chest radiographs were assessed independently by three experienced readers, and the yearly declines in forced expiratory volume in one second and forced vital capacity were estimated from two to four (mean 3.45) serial spirometric readings. Estimates of individual dust exposure were based on extensive historical data on hygiene. All but 11 patients were no longer exposed to dust by the start of follow up, but 24 (45%) of 53 patients who had simple silicosis and 11 (55%) of 20 who had the complicated disease showed radiological evidence of disease progression. In patients who had simple silicosis and showed no radiological progression the yearly declines in forced expiratory volume in one second and forced vital capacity were modest (64 ml/year and 59 ml/year, respectively), whereas significantly greater declines in lung function were seen in those who showed radiological evidence of progression (97 ml/year and 95 ml/year, respectively). In addition to radiological progression the previous average dust concentration to which patients had been exposed also influenced declines in both forced expiratory volume in one second and forced vital capacity after allowing for the effects of age, smoking, duration of exposure, history of tuberculosis, initial state of disease, and baseline lung function. The probability of radiological progression was most strongly influenced by the average dust concentration previously exposed to. The progression of simple silicosis is thus accompanied by appreciable declines in lung function and is strongly affected by previous levels of exposure to dust.

A survey of the respiratory health of silica-exposed gemstone workers in Hong Kong

Respiratory symptoms and radiographic and lung function alterations were studied in a cross-sectional survey of gemstone workers in Hong Kong. The study population included a group of grinders, polishers, and buffers who were heavily exposed to dust (principally free silica) and a less exposed group of cutters and carvers. Among all 218 male workers who answered the respiratory questionnaire, heavily exposed workers reported significantly higher prevalence of respiratory symptoms suggestive of mucus hypersecretion. Radiological pneumoconiosis defined as opacities with profusion of 1/0 and above was found in 27% of 157 workers who accepted radiographic and lung function examination. Radiological opacities were significantly related to increasing years of employment in both groups of workers after taking into account age and smoking habits. Decline in forced vital capacity (FVC) was significantly related to increasing years of employment in both groups after allowing for the effects of age, height, and smoking. A modest decline in forced expiratory volume in one second (FEV1) was related to dust exposure which was of borderline statistical significance in polishers and buffers who smoked. Radiological pneumoconiosis did not have an independent effect on lung function when allowance was made for dust exposure.

A case-referent study of cancer of the nasal cavity and sinuses in Hong Kong

A case-referent study of cancer of the nasal cavity and sinuses (NCS) was conducted in Hong Kong where textile and garment manufacturing are major industries. The study population included 225 nasal cavity and sinus cancer cases (NCS), 224 nasopharyngeal cancer (NPC) referents, and 226 all other malignancies (AOM) referents, diagnosed at the Institute of Radiology and Oncology from 1974 through 1981. A strikingly close similarity in occupational distribution between NPC referents and NCS cases was found. Compared to AOM referents, statistically significantly elevated odds ratios of association with nasal cavity and sinuses cancer were found among textile workers (OR, 2.93), fishermen (OR, 3.38), farmers (OR, 1.94) and construction workers (OR, 1.91) particularly for textile workers and fishermen with more than 15 years of employment (textile workers, OR 7.39), (fishermen, OR 3.72). Among textile workers, somewhat more elevated risks were found among weavers (OR, 4.72) after controlling for employment years. Slightly but not statistically significant elevated relative risks of NCS were also associated with those who smoked (OR 1.40) and those who were locally born in Hong Kong (OR 1.53). The known risk of nasopharyngeal cancer among fishermen and those originating from the southern Chinese province of Guangdong was also evident. These findings confirm an association of nasal cavity and sinuses cancer with textile work which has been previously suggested by other studies and provide new leads for further research on the environmental aetiology of cancer of the nasal cavity, sinuses and nasopharynx.

An outbreak of illness after occupational exposure to ozone and acid chlorides

New labelling processes installed without adequate ventilation control in an electric motor factory exposed production line workers to toxic gases. Symptoms of eye and respiratory tract irritation together with complaints of headache, fever, chills, dizziness, malaise, general weakness, nausea, and vomiting were widespread. Chest signs, radiographic abnormalities, reduction in ventilatory function, and blood gas abnormalities were found in some cases. Epidemiological analysis of the spatial and temporal distribution of cases supported an exposure effect relationship. Investigations suggested ozone and possibly phosgene and associated trichloroacetyl chlorides as the toxic agents that were generated by an ultraviolet print curing arrangement and perchloroethylene used as a cleaning solvent.