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Biomedical subjects

K T Tan

Publications and source records attributed to K T Tan.

At least 37 records · Page 2Linked to original sources
PubMed1996

Blood cyst of the tricuspid valve.

Blood-filled cysts of the heart valves are commonly reported at postmortem examination of infants but are rarely seen in older children and adults. These cysts appear to be benign lesions and should be removed only if they cause problems. We present the case of a patient with a tricuspid valve blood cyst that was surgically removed and then discuss the differential diagnosis and management of these cysts. When a cardiac mass has features suggestive of a blood cyst, radical resection should not be performed unless histologic confirmation of tumor is obtained.

Child, Preschool↗
PubMed1996

Biomarkers of exposure to low concentrations of benzene: a field assessment.

OBJECTIVE: To carry out a comprehensive field investigation to evaluate various conventional and recently developed biomarkers for exposure to low concentrations of benzene. METHODS: Analyses were carried out on environmental air, unmetabolised benzene in blood and urine, urinary trans, transmuconic acid, and three major phenolic metabolites of benzene: phenol, catechol, and hydroquinone. Validations of these biomarkers were performed on 131 never smokers occupationally exposed to the time weighed average benzene concentration of 0.25 ppm (range, 0.01 to 3.5 ppm). RESULTS: Among the six biomarkers studied, unmetabolised benzene in urine correlated best with environmental benzene concentration (correlation coefficient, r = 0.76), followed by benzene in blood (r = 0.64). When urinary metabolites were compared with environmental benzene, trans, trans-muconic acid showed a close correlation (r = 0.53) followed by hydroquinone (r = 0.44), and to a lesser extent with urinary phenol (r = 0.38). No correlation was found between catechol and environmental benzene concentrations. Although unmetabolised benzene in urine correlates best with benzene exposure, owing to serious technical drawbacks, its use is limited. Among the metabolites, trans, trans-muconic acid seems to be more reliable than other phenolic compounds. Nevertheless, detailed analyses failed to show that it is specific for monitoring benzene exposures below 0.25 ppm. CONCLUSION: The overall results suggest that most of the currently available biomarkers are unable to provide sufficient specificity for monitoring of low concentrations of benzene exposure. If a lower occupational exposure limit for benzene is to be considered, the reliability of the biomarker and the technical limitations of measurements have to be carefully validated.

Air↗
PubMed1995

Environmental and biological monitoring of occupational exposure to 1,1,1-trichloroethane.

Fifty workers involved in various degreasing and cleaning processes using 1,1,1-trichloroethane (1,1,1-TCE) were studied with respect to personal and static exposures. In addition, end-of-shift expired air and venous blood samples were taken for analysis of the parent compound. Urinary samples were also obtained at the same time for analysis of its metabolites-trichloroethanol (TCOH) and trichloracetic acid (TCA). The results show that open/manual degreasing processes generate the highest environmental solvent levels (mean = 819.9 mg/m3; SD = 781.9 mg/m3) followed by jet-spray cleaning (mean = 460.5 mg/m3; SD = 292.4 mg/m3), vapour degreasing (mean = 365.3 mg/m3; SD = 279.9 mg/m3) and ultrasonic degreasing (mean = 134.7 mg/m3; SD = 121.0 mg/m3). Personal exposure levels were well correlated with concentrations of 1,1,1-TCE in end-of-shift expired air (r = 0.81) and venous blood samples (r = 0.88) but only moderately correlated with concentrations of its metabolites in urine (r = 0.49 for TCOH; r = 0.58 for TCA). Static (area) samples were poorly correlated with the biological exposure indices studied.

Air↗
PubMed1995

Cadmium hazard in silver brazing.

This study evaluates the usage of cadmium-containing silver brazing alloys in Singapore and the potential cadmium hazard from its use. Of the 137 factories which responded to the survey questionnaire, only 28 (20.4%) carried out brazing. Of these, only 7 factories used cadmium-containing filler alloys. One hundred and six out of 123 workers from one of these factories had cadmium-in-blood concentrations exceeding 10 mcg/l. Thirty-one (29.2%) of the workers with excessive cadmium absorption had urinary beta-2 microglobulin levels exceeding 28 mcg/g creat. Workers in the other factories who were intermittently exposed had cadmium-in-blood concentrations of 10 mcg/l and below.

Alloys↗
PubMed1995

Fatal gassing due to methylene chloride - a case report.

Methylene chloride is a major component of paint and varnish strippers. Due to its high volatility, its use in unventilated or poorly ventilated confined spaces poses a serious health hazard as a result of accumulation of the solvent vapour. At high levels, methylene chloride can cause severe central nervous system depression and ultimately death, as illustrated in this case report. The importance of adequate forced ventilation, utilisation of proper personal protective equipment and enforcement of a permit-to-work system during work with solvents in confined spaces is emphasised.

Adult↗
PubMed1994

Pregnancy and delivery in primigravidae aged 35 and over.

A retrospective study was performed on 111 consecutive primigravidae aged 35 and above (study group) who delivered in the Gynaecological Oncology Department, Kandang Kerbau Hospital, Singapore during the two-year period (1990 and 1991). For comparison, all the 10,189 patients in the department who were delivered during the same time period were also analysed and served as the control group. The aim of the study was to examine the risks involved with advanced maternal age, the obstetric performance and neonatal outcome of both groups in the context of modern obstetric care in Singapore. In the study group, pre-eclampsia was the commonest antenatal complication (17.1%), followed by preterm labour (16.2%) and diabetes mellitus (including impaired glucose tolerance test) (16.2%). In the control group, the corresponding incidences were 10.8%, 6.3% and 2.8% respectively. The incidence of labour induction (28.8%) and instrumental deliveries (31.5%) were higher in the study group than in the control group (7.1% and 7.3% respectively). The Caesarean section rate was twice as common in the study group (32.4%) than in the control group (16%). Only 15 patients (13.5%) had amniocentesis performed. The majority of patients (41.5%) who did not have amniocentesis were 35 years of age at delivery. The perinatal mortality rate of the study group was similar to that of the control group. There were no maternal deaths.

Adult↗
PubMed1994

A case of occupational asthma due to barley grain dust.

We report a case of occupational asthma due to barley grain dust, species Hordeum Vulgare L, in a 32-year-old storeman of a trading company's department that dealt with packaging of flour, barley and peanuts. He developed immediate symptoms of sneezing, cough and dyspnoea on exposure to barley only. These symptoms showed work relationship. He became asymptomatic after his transfer to another department dealing with sales only. Bronchial provocation testing to the barley confirmed the diagnosis.

Adult↗
PubMed1993

Exposure to neurotoxic metals among workers in Singapore: an overview.

The extent of occupational exposure to inorganic lead, manganese, arsenic and inorganic mercury in Singapore was determined from the results of Statutory Medical Examinations and environmental monitoring carried out by the Department of Industrial Health in 1989. There were 786 workers exposed to lead. Of these, 7.8 per cent had blood levels greater than 40 micrograms/dl. There were 67 workers exposed to mercury, 11.9 per cent of whom had urinary mercury levels greater than 50 micrograms/l. There were 101 and 144 workers exposed to arsenic and manganese respectively. None of the biological samples exceeded the health-based limits. A review of local studies showed that some of the exposed workers had neurophysiological and neurobehavioural changes.

Arsenic↗
PubMed1993

Burnisher's asthma--a case due to ammonia from silverware polishing.

A 39-year-old man with no past or family history of asthma developed asthmatic symptoms five months after working as a burnisher in a hotel. He polished brass or silverware using "brasso" or "silvo" respectively. He noticed symptoms only when using "silvo". Specific bronchial provocation testing (BPT) to "brasso" was negative. Specific BPT to "silvo" produced a dual asthmatic reaction. Ammonia was present in both polishes. The ammonia-in-air levels during polishing was 8-15 ppm with "silvo" and less than 1 ppm with "brasso". A specific BPT to 12 ppm of ammonia produced an immediate asthmatic reaction. Our opinion is that he had occupational asthma from the ammonia liberated while polishing silverware with "silvo". Ammonia has been reported to cause asthma. However, there have been no previous reports of occupational asthma among burnishers doing silver polishing.

Adult↗
PubMed1993

Neurobehavioural effects on workers in a video tape manufacturing factory in Singapore.

This study was carried out in a video tape manufacturing factory in Singapore where workers were exposed to mixed solvents consisting of methyl ethyl ketone (MEK), cyclohexanone (CHE), tetrahydrofuran (THF), and toluene (TOL). The objectives were to quantify workers' exposure to the various solvents and to evaluate if there were any neurobehavioural changes among the workers compared to controls. Nineteen exposed workers out of the workforce of forty-five were studied. Twenty-six workers (with no exposure) matched for ethnic group, age, and years of education served as controls. Eight-hour personal environmental samples were analyzed for the 19 workers along with symptom questionnaires, clinical examinations, and neurobehavioural tests including the Santa Ana Dexterity, Finger Tapping, Digit Span, and Visual Reproduction tests. The mean TWA concentrations for MEK, THF, CHE, and TOL were all below the current American Conference of Governmental Industrial Hygienists Threshold Limit Values (TLV). However, the total solvents concentration index exceed unity in one of the work areas. Significant differences were observed for prevalence of headache, and eyes and nose irritation among the exposed workers. There were also significant differences for the Santa Ana test for both-hands, Digit Span test and Visual Reproduction test. However, no dose-effect relation between behavioral scores and airborne solvent exposure was noted. The study suggests that solvent-exposed workers in video tape manufacturing plants may have poorer visual motor control and recent memory impairment (visual and verbal) than unexposed workers. Dermal absorption of solvents may have played a role in these results by increasing workers exposure.

Adult↗
PubMed1992

An epidemiological survey of respiratory morbidity among granite quarry workers in Singapore: radiological abnormalities.

This report presents baseline findings from the first of a series of epidemiological studies to evaluate inter alia the effects of control measures introduced in 1972-79 to reduce dust exposure in all quarries in Singapore. The prevalence of radiological abnormalities among 219 currently employed quarry workers were estimated according to a number of parameters of dust exposure. Large-sized chest x-ray films were read, independently and in random order, by a panel of three experienced readers, who were "blinded" to the personal particulars and exposure of the subjects, using standard chest x-ray films to record opacities according to the International Standard Classification of Radiographs of Pneumoconioses. Silicosis as defined by radiological small opacities (both rounded and irregular) of profusion 1/1 or greater as read by at least two readers were noted in 11 subjects. The prevalence of silicosis was 12.5% in highly exposed drilling and crushing workers, and 0.8% in maintenance and transportation workers with low level exposure to granite dust. Among those who were first exposed to granite dust after 1979, no cases of silicosis were noted in any quarry worker. It is concluded that reduction in dust exposure since 1979 has so far been successful in producing nil or negligible risks of silicosis among active quarry workers over ten years, but further follow-up studies are needed.

Adult↗
PubMed1992

An epidemiological survey of respiratory morbidity among granite quarry workers in Singapore: chronic bronchitis and lung function impairment.

Respiratory symptoms of chronic bronchitis and measurements of lung function were studied in an epidemiological survey of the total population of workers currently employed in granite quarries in Singapore. There were 85 rock drilling and crushing workers with current exposure in high levels of silica dust. Their respiratory parameters were studied with reference to an internal comparison group of 154 quarry maintenance and transport workers with low dust exposure, and an external comparison group of 148 Telecoms postal delivery workers with no granite dust exposure. The highly exposed workers showed greater prevalences of chronic cough and phlegm, a mean reduction of 5% in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The increased respiratory morbidity were independent of other factors such as age and smoking. Similar results were also noted after excluding those with silicosis (defined radiologically as profusion greater than 1/1 as read by at least two of three readers). This study strongly indicates a demonstrable risk of "occupational" bronchitis (mucus hypersecretion) and obstructive and restrictive lung function impairment, apart from the "classical" risk of silicosis. Measures taken to protect the health of workers exposed to silica dust should also be based on considerations taken to protect against the risk of these respiratory disorders as well.

Adult↗
PubMed1992

Retinal artery occlusion in a diver.

The clinical manifestation of decompression disorders is highly variable, ranging from mild rashes or joint pains to central nervous system symptoms like scotomata, paralysis and death. The diagnosis is easily overlooked, especially if an occupational history is not obtained. Recompression treatment with hyperbaric oxygen is the specific treatment for decompression sickness and air embolism. Prompt recognition and treatment are vital to recovery. However, there is a place for treatment of decompression disorders and embolism even when significant delay of up to 14 days has occurred. This case report discusses decompression disorders in relation to an unskilled fisherman diver who present with retinal artery occlusion. Decompression disorder leading to retinal artery occlusion is a very rare presentation. The difficulty of diagnosis is discussed as well as the result of delayed hyperbaric treatment.

Adult↗
PubMed1991

Biological monitoring of occupational exposure to methyl ethyl ketone.

This study was conducted to evaluate the usefulness of three commonly used methods of biological monitoring for worker exposed to methyl ethyl ketone (MEK) under field conditions using blood, breath and urine. Environmental MEK exposures were measured by personal sampling with carbon-felt dosimeters. The correlation coefficient (r) between the time-weighted average (TWA) MEK concentration in air and the MEK concentration in blood collected at the end of the work shift was 0.85. The correlation coefficient between the TWA MEK level in air and the concentration exhaled in the breath of workers at the end of the work shift was 0.71. The end-of-shift urinary MEK excretion correlated best with the environmental concentration (r = 0.89). Correlations became lower after urine samples had been corrected for urinary creatinine (r = 0.83) or specific gravity (r = 0.73). After 8 h exposure to 200 ppm MEK, the corresponding end-of-shift urinary excretion was 5.1 mumol/l or 4.11 mg/g creatinine. This value is higher than that previously found in some studies, the difference probably being due to the physical activities of the present workers and their extensive skin contact with the solvent. The kinetics of inhaled MEK was also studied in eight subjects. Breath and urine samples were collected during the 8-h work shift on 2 consecutive Mondays. The results showed that urinary MEK excretion rose steadily until the end of exposure, whereas the MEK concentration in exhaled air varied markedly throughout the day.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Overnight (1 mg) dexamethasone suppression testing reliably distinguishes non-cushingoid obesity from Cushing's syndrome.

To determine the sensitivity of the overnight 1-mg dexamethasone suppression test in diagnosing Cushing's syndrome, we evaluated the cortisol responses of 55 subjects (25 non-obese individuals with body mass index less than 25 kg/m2, 20 obese individuals with body mass index greater than 30 kg/m2, and 10 patients with surgically proven Cushing's syndrome) following ingestion of 1 mg dexamethasone at midnight. The basal 8 AM plasma cortisol levels among non-obese and obese individuals and patients with Cushing's syndrome were 310 +/- 85, 377 +/- 91, and 813 +/- 270 nmol/L, respectively. Following 1 mg of dexamethasone, Cushing's syndrome patients showed minimal suppression of cortisol to 609 +/- 180 nmol/L (P = 0.79). Non-obese and obese individuals suppressed to 18.7 +/- 6.0 nmol/L (P less than 0.001) and 22 +/- 7.1 nmol/L (P = 0.003), respectively. The results demonstrated similar cortisol responses to overnight dexamethasone suppression in obese and non-obese groups, and clearly distinguished these subjects from those with Cushing's syndrome. Obesity is not a confounding factor in the 1-mg dexamethasone suppression test.

Adult↗
PubMed1991

Biological monitoring of occupational exposure to tetrahydrofuran.

Occupational exposure to tetrahydrofuran (THF) was studied by analysis of environmental air, blood, alveolar air, and urine from 58 workers in a video tape manufacturing plant. Head space gas chromatography (GC) with an FID detector was used for determination of THF concentration in alveolar air, urine, and blood. Environmental exposure to THF was measured by personal sampling with a carbon felt passive dosimeter. When the end of shift urinary THF concentrations were compared with environmental time weighted average (TWA) values, urinary THF concentration corrected for specific gravity correlated well with THF concentration in air (r = 0.88), and uncorrected urinary THF concentration gave a similar result (r = 0.86). Correction for creatinine in urine weakened the correlation (r = 0.56). For exposure at the TWA concentration of 200 ppm the extrapolated concentration of THF was 33 mumol/l in blood and 111.9 mumol/l (61 mumol/g creatinine) or 109 mumol/l at a specific gravity of 1.018 in urine. The correlation between exposure to THF and its concentration in exhaled breath and blood was low (r = 0.61 and 0.68 respectively). Laboratory methodological considerations together with the good correlation between urinary THF concentration and the environmental concentration suggest that THF concentration in urine is a useful biological indicator of occupational exposure to THF.

Adult↗
PubMed1991

Monitoring of exposure to cyclohexanone through the analysis of breath and urine.

Occupational exposure to cyclohexanone was studied for 59 workers through the analysis of environmental air, alveolar air, and urinary cyclohexanol. Environmental cyclohexanone exposure was measured by personal sampling with a carbon-felt passive dosimeter. Cyclohexanone in alveolar air and cyclohexanol in urine were determined with gas chromatography with a flame ionization detector. The end-of-shift urinary cyclohexanol levels correlated well with the time-weighted average environmental cyclohexanone values (r = 0.66). Urinary cyclohexanol corrected for creatinine correlated best with cyclohexanone in air (r = 0.77); when corrected for specific gravity, it gave a similar correlation coefficient (r = 0.73). When the time-weighted average of the exposure was 25 ppm, the corresponding calculated concentration for urinary cyclohexanol was 54.5 mg/1, 23.3 mg/g of creatinine, or 43.5 mg/l at a specific gravity of 1.018. The relationship between cyclohexanone exposure and its concentration in exhaled breath was found to be poorer than that for cyclohexanone exposure and the urinary metabolite (r = 0.51).

Adolescent↗