Baker's asthma: a case report

Bakers are known to experience respiratory complaints ranging from allergic rhinitis to chronic bronchitis and asthma. We report here the first confirmed case of baker's asthma in Singapore. The patient is a 40 year-old Chinese male, working at a biscuit factory for the last 14 years as a mixer. He developed asthmatic attacks five years after joining the factory and had been on bronchodilators and oral steroids. He was confirmed to have occupational asthma due to wheat flour, following a bronchial challenge test. He was subsequently transferred to another section and there was marked improvement in the frequency of attacks and the peak expiratory flow rate. This case illustrates the need to consider workplace factors in the diagnosis and management of asthma among the working population. Medical treatment alone is insufficient in the management of occupational and work-related asthma.

Electrothermal atomic absorption spectrometric determination of cadmium and nickel in urine

This paper describes two relatively simple methods for the microdetermination of urinary cadmium (U-Cd) and urinary nickel (U-Ni) using electrothermal atomic absorption spectrometry. Reduction of nonspecific absorption interferences was achieved by temperature programming and background correction using a deuterium arc lamp. Within-run CVs were less than 5% for both U-Cd and U-Ni. Day-to-day variation was less than 8.1% for U-Cd and less than 8.0% for U-Ni. The typical limit for detection was 0.08 micrograms/L for U-Cd and 0.1 micrograms/L for U-Ni. The methods described are useful for mass screening of low level exposure to Cd or Ni.

Incidence of primary liver cancer in Singapore, 1968-1982

Based on data collected by the population-based Singapore Cancer Registry over the period 1968 to 1982, baseline epidemiological characteristics and incidence trends of primary liver cancer were described. This will facilitate the interpretation of future trends, especially in the light of new interventions such as hepatitis B immunisation. The primary liver cancer incidence is four times higher in males than in females, with the incidence peaked in the seventh decade. The incidence rate was higher in the Chinese than in Malays and Indians and marginally higher among foreign born than Singapore born Chinese. A general declining trend in liver cancer incidence was especially notable in the local born Chinese. Misclassification of metastatic carcinomas in the earlier years of cancer registration may have contributed to the initial higher incidence. Definitive decrease in incidence as a result of hepatitis immunisation will only be seen in another two to three decades.

Renal tubular function of workers exposed to low levels of cadmium

Cadmium induced renal tubular effects were examined in 65 female workers in a factory manufacturing nickel cadmium batteries. Urinary beta 2-microglobulin (beta 2m), urinary N-acetyl-D-glucosaminidase activity (NAG), and serum creatinine and serum urea concentrations were used to assess the renal effects. Of the four measures, only urinary NAG and urinary beta 2m showed a strong positive correlation with blood cadmium concentrations (r = 0.49 and 0.43 respectively); NAG showed a weaker correlation with urinary cadmium concentrations (r = 0.35). Urinary beta 2m has weak correlation with urinary cadmium (r = 0.04). Only urinary NAG showed a significant deterioration in renal function among the exposed group. NAG detects the largest proportion of abnormalities among the exposed group. Abnormal urinary beta 2m is detected in only 15.4% of the workers, half of whom have blood cadmium above 10 micrograms/l. The proportion of abnormalities detected by urinary NAG differs significantly from the proportion of abnormalities detected by urinary beta 2m (p less than 0.01). The age adjusted mean urinary NAG excretion showed a significant rise with urinary cadmium of above 3 micrograms/g creatinine. Urinary beta 2m failed to show any significant rise. With blood cadmium concentrations, the age adjusted mean urinary NAG excretion showed a rise from 1 microgram/l of blood cadmium followed by a plateau between blood cadmium concentrations of 3-10 micrograms/l. No significant rise in mean urinary excretion in beta 2m was seen until blood cadmium concentrations exceeded 10 micrograms/l.

Neurochemical effect of lead exposure: a study on catecholamine metabolism

In an attempt to examine the neurochemical changes of lead exposure, a study was conducted on 106 lead workers and a control group of 25 nonexposed workers. The urinary excretion of major catecholamine metabolites, homovanillic acid (HVA), and vanillylmandellic acid (VMA) were measured. Workers exposed to lead had a mean blood lead concentration of 43.2 micrograms/100 ml, whereas the concentration for workers not exposed to lead was 12.7 micrograms/100 ml. Urinary HVA was significantly elevated in the exposed group when compared with controls (p less than 0.01). HVA was also found to be associated with an increase of lead in blood. Although not statistically significant, the VMA excretion was also noted to be moderately elevated; however, it is recognized that the present study was unable to establish a highly significant dose-response relationship between lead exposure and HVA excretion, as has been reported earlier in lead-poisoned children.

Some reflections on the global and Asia-Pacific situations in occupational health education and training

In the last two decades, there have been dramatic developments in the field of occupational health. With it, the importance of occupational health training and education is greatly appreciated.

In a worldwide questionnaire survey on occupational health teaching in schools of medicine, 69.9% of the schools have some form of occupational health teaching for medical undergraduates. The total number of hours varies considerably but on average is 32.7 hours. Some occupational health teaching might however have been classified under other subject headings.

In the Asia-Pacific region, several postgraduate degree courses were recently established. Continuing educational courses and short courses are on the rise. To take advantage of the existing primary health care systems, special courses for public health workers and primary health care personnel have been conducted. In the past, interest in occupational health education and training tended to be overshadowed by advances in epidemiology and pathogenesis of occupational diseases. Based on our experience over the past few years, occupational health training and education will gather greater momentum worldwide and in the Asia-Pacific region in particular.

Transit time analysis of the forced expiratory spirogram of fire-fighters

Analysis of the forced expiratory spirogram using time as the primary variable had been shown to be a promising method for detecting small airway dysfunction. This paper describes its application on 277 fire-fighters. Spirometry was performed when the fire-fighters were at rest and had not been fighting fires for the previous 24 hours. The best of three spirograms were used to compute the mean transit time (MTT). Through multiple linear regression analysis, age was the only factor that was significantly associated with MTT. The regression coefficients for age of smoking and non-smoking fire-fighters were nearly equal (0.011 and 0.010 seconds per year respectively). When 28 pairs of smoking and non-smoking fire-fighters were matched for age, duration of service, ethnicity and job groups, their average MTT were not significantly different. An increasing age-adjusted mean MTT was seen among the non-smoking fire-fighters with job groups requiring greater exposure to fire-fighting. Normal smokers had been shown to have a much greater regression coefficient for age on MTT when compared to normal nonsmokers. When compared with this study, the regression equation for MTT of non-smoking fire-fighters differed markedly from that of normal non-smokers and approached that of normal smokers. Coupled with the 'dose-response' relationship shown in the non-smoking fire-fighters, this study provides evidence of pulmonary dysfunction in fire-fighters. This pulmonary dysfunction may be localised in the small airways.

Shiftwork and work injuries in an iron and steel mill

A study on work injuries that occurred over a five-year period was conducted in an iron and steel mill employing over 1000 workers. Of all the 921 injuries which required more than one day's sick leave, over 40% (383 cases) happened during the morning shift (0700-1500 hours), 210 cases occurred in the afternoon shift (1500-2300 hours) and only 150 cases were reported during the night shift. There were two injury peaks throughout the day, one at mid-morning (between 0900 and 1000 hours) and the other towards the mid-afternoon (1400-1500 hours). It was observed that hand injuries were more common during the morning and afternoon shifts and foot injuries normally occurred at night. 'Fall' was one of the main causes of accidents at night, whereas 'struck by' heavy objects and 'burn' were more common during the day. Although there were more accidents during the morning and afternoon shifts, work injuries which occurred at night generally required a longer duration of sick leave. This suggests that accidents which happened at night were more serious. It is believed that the work habits, shift systems and work environment have a substantial influence on these accidents.

Health risk appraisal by ventilatory capacity

Ventilatory evaluation has been widely used to investigate occupational effects on the respiratory system. This paper reports on a cross-sectional epidemiological study in Singapore carried out on four different occupational groups. A total of 999 male workers were evaluated by a spirometer interphased with a microcomputer. Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) of each worker were measured. The results suggested that ventilatory capacities are significantly correlated to age and height. Smokers, however, did not differ significantly from non-smokers in their FEV1 and FVC values. This was probably due to the fact that they were relatively light smokers. After adjustment for age and height, the Chinese were found to have slightly higher ventilatory capacities than the Malays in both the FEV1 and FVC. One important observation from the present study was that occupation was found to have a significant influence on lung capacity. Aircraft mechanics and firemen were found to have a higher mean FEV1 than other occupational groups-probably due to the stringent recruiting criteria of these two groups of workers. However, firemen also tended to have a greater reduction in lung volumes with increasing age. The rates of decrease in FEV1 for firemen, blue collar telecommunications workers, aircraft mechanics and sedentary workers were 0.031, 0.029, 0.026 and 0.016 litres/year, respectively. The rate of decrease in FVC showed a similar pattern of 0.022, 0.019, 0.011 and 0.006 litres/year, respectively. This finding indicates that sedentary workers appear to have a lower respiratory health risk compared with their counterparts in other sectors. In contrast, firemen are constantly facing possible respiratory hazards. As demonstrated here, measurement of ventilatory function could be a useful predictor for surveillance of respiratory hazards. However, certain factors like age, height, ethnic origin and smoking habits must be considered in the analysis and interpretation of results.