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Biomedical subjects

S E Chia

Publications and source records attributed to S E Chia.

At least 37 records · Page 2Linked to original sources
PubMed1999

Acute mercury vapour poisoning in a shipyard worker--a case report.

Acute mercury vapour poisoning is a serious, potentially fatal but fortunately rarely encountered problem. It is most commonly due to industrial accidents. The vapour is a direct respiratory tract irritant as well as a cell poison, exerting its greatest effects in the lungs, nervous system, kidneys and liver. We present a case of mercury vapour poisoning in a shipyard workers presenting as an acute chemical pneumonitis, which resolved with aggressive supportive therapy. Further investigations later revealed transient mild neuropsychiatric symptoms, and residual peripheral neuropathy. No chelation therapy was instituted. The detailed investigative work that led to the discovery of the source of mercury is also presented. This case alerts us to the potential hazard to shipyard workers who may work in ships previously carrying oil contaminated with mercury. There have been no previous reports of mercury poisoning in shipyard workers. A high index of suspicion leading to early diagnosis and institution of appropriate supportive measures in suspected cases can be life-saving.

Acute Disease↗
PubMed1998

Urinary homovanillic acid (HVA) and vanillymandelic acid (VMA) in workers exposed to manganese dust.

The neurotoxicity of manganese (Mn) is well known, however, the neurochemical effect caused by this metal is less well investigated. In this study, urinary homovanillic acid (HVA) and vanillymandelic acid (VMA), two end products of catecholamine metabolism, were measured in 39 workers chronically exposed to Mn in a manganese smelting plant. The average duration of Mn exposure was 17.4 yr. Nineteen nonexposed workers were also studied. Concentrations of Mn in serum (MnS) and in urine (MnU) were measured by Zeeman graphite furnace atomic absorption spectrophotometry (ZAAS), and HVA and VMA determined by high performance liquid chromatography (HPLC). For Mn-exposed workers, the concentration of MnS was nearly 2.8 times (1.61 +/- 0.16 mg/L vs 0.56 +/- 0.16 mg/L) and MnU about 4.5 times higher (7.62 +/- 0.17 mg/L vs 1.69 +/- 0.16 mg/L) than the nonexposed. Although the geometric mean concentration of HVA in exposed workers was similar to that of the nonexposed (3.09 +/- 1.39 mg/g cre. vs 2.99 +/- 1.40 mg/g cre.), the VMA concentration was significantly higher (3.02 +/- 1.43 mg/g cre. vs 2.49 +/- 1.58 mg/g cre., p = 0.033). Multiple regression analysis showed that although there were no correlations between any of these parameters with the duration of exposure to Mn, both HVA and VMA showed significant correlations with increase in MnS and MnU. These data provide evidence that exposure to Mn was associated with measurable increase in catecholamine metabolites. This finding is compatible with recent observations in laboratory animals that Mn interferes with neurochemical metabolism.

Adult↗
PubMed1998

Outdoor work and the risk of pterygia: a case-control study.

AIM: To investigate the relationship between outdoor work and pterygium formation in a hospital-based case-control study in Singapore. METHOD: Sixty-one patients with pterygium (49 males, mean age 54.2 years) and 125 controls (41 males, mean age 50.2 years), excluding patients with cataract and age-related macular degeneration presenting at outpatient clinics of the Singapore National Eye Centre were interviewed face-to-face with a standard questionnaire. Demographic data and information on outdoor work and eye protection, were collected. RESULTS: Thirty-eight subjects (20.4%) were outdoor workers and 148 (79.6%) were indoor workers. Outdoor workers were more likely to be male smokers and alcohol drinkers with lower family income and higher sunlight exposure than indoor workers. The crude odds ratio for pterygium in outdoor workers was 7.0 (95% confidence interval 3.2, 15.3). The adjusted odds ratio was 4.2 (95% confidence interval 1.7, 10.1). CONCLUSION: There is a statistically significant association between outdoor work and pterygium formation, which may be related to the higher exposure to sunlight and dust in outdoor workers. Efforts may be made to educate outdoor workers to wear proper equipment to protect their eyes against excessive sunlight.

Adult↗
PubMed1998

Neuropathy in non-insulin-dependent diabetes mellitus. The significance of symptoms.

OBJECTIVE: Clinical evaluation of significance of symptoms suggestive of neuropathy in non-insulin-dependent diabetics in general practice. DESIGN: Case control study. Interviewer-administered questionnaire. Physical examination by general practitioner researcher. SETTING: Government family practice clinic in Singapore. SUBJECTS: 55 patients with non-insulin-dependent diabetes (NIDDM) aged 35-84 years (51% males), and 53 non-diabetic controls matched for age (+/- 5 years) and gender. MAIN OUTCOME MEASURES: Proportions of subjects with presence of symptoms and physical signs. RESULTS: More patients than controls experienced symptoms suggestive of distal neuropathy (paraesthesiae: 13 vs. 4%), and lower extremity proximal myopathy (weakness climbing stairs: 42 vs. 19%, getting up from squatting position: 31 vs. 11%). No difference in proportions of patients and controls experiencing symptoms suggestive of autonomic neuropathy. More patients than controls had absent tendon reflexes (35 vs. 13%) and weaker hip muscles (24 vs. 6%). Of all who experienced symptoms indicating peripheral neuropathy, 36% of patients had absent tendon reflexes, compared with 8% of controls; and of those who experienced weakness of hip muscles, 31% of patients and 12% of controls had diminished power in the hip muscles. CONCLUSION: Symptoms suggestive of diabetic neuropathy are common and should be asked about in the routine follow-up of patients with diabetes. Up to a third of patients with symptoms will have clinical signs of diabetic neuropathy.

Adult↗
PubMed1998

What constitutes a normal seminal analysis? Semen parameters of 243 fertile men.

A cross-sectional study was conducted to determine the semen parameters (i.e. volume, concentration, motility, viability and normal morphology) of proven fertile males in Singapore and compare it with the World Health Organization (WHO) recommended normal values and to examine some factors that may affect spermatogenesis. A total of 243 men, whose wives were pregnant at the time of collection of semen, provided a semen sample each after sexual abstinence for 3 days. A questionnaire was used to elicit occupational exposure, alcoholic consumption, smoking history and past significant medical history. Most subjects had normal sperm volume (56.4%), concentration (79.8%), motility (69.5%) and viability (53.5%) based on WHO criteria. However, fertile men had a low mean percentage of normal sperm morphology (20.0%), although they were normally distributed. Cigarette smoking was associated with significantly lower semen volumes even after adjusting for alcohol consumption. The sperm parameters (i.e. volume, density, motility, viability and normal morphology) were not significantly associated with ethnic differences. The WHO criterion for normal sperm morphology is too stringent, and should be adopted with caution. Normal sperm morphology is but one of many parameters for assessment of fertility. Social alcohol consumption, cigarette smoking, and 'recent fever' did not appear to affect sperm quality in this group of fertile men.

Adult↗
PubMed1998

Effects of chronic exposure to low doses of trichloroethylene on steroid hormone and insulin levels in normal men.

The aim of this study was to examine the serum levels of insulin and some adrenal steroid hormones in men chronically exposed to low doses of trichloroethylene (TCE). A total of 85 workers participated in this study. Each worker had urine collected and analyzed for trichloroacetic acids (UTCA) on the same day that a blood sample was taken for analyses of serum testosterone, sex hormone-binding globulin (SHBG), androstenedione, cortisol, aldosterone, and insulin. The mean concentration of environmental TCE was 29.6 ppm and the mean UTCA was 22.4 mg/g creatinine (range 0.8-136.4). TCE exposure did not cause any significant changes to the adrenal steroid hormone productions. The results showed that UTCA was significantly correlated to serum insulin levels. Insulin and SHBG responded in tandem, with the highest levels found in workers exposed to TCE for less than 2 years; levels of both parameters were significantly lowered in those exposed for more than 2 years. A triphasic response in insulin levels to TCE, which depended on the duration of exposure, was noted. Initial exposure caused an acute rise in insulin levels. This was followed by a fall to normal levels in those exposed 2-4 years and then a slight rise in those exposed for more than 6 years. The mechanism for this pattern of response to TCE exposure is yet unknown.

Adrenal Cortex Hormones↗
PubMed1997

Does the increase of 8-hydroxydeoxyguanosine lead to poor sperm quality?

Several studies have suggested a population-wide decline in the quality of human semen during the past three decades, but the mechanism remains unclear. It was proved that damage to the DNA of germ cells would lead to mutation, and 8-hydroxydeoxyguanosine (8-OHdG), one of the major products of oxidative damage to DNA, may serve as one of the important factors to affect the sperm quality. In the present paper, 67 semen samples were collected to analyze the sperm quality (density, sperm number, motility, normal head, etc.), and 8-OHdG was measured in DNA isolated from the same sperm samples. The results showed that a significant inverse correlation exists between 8-OHdG/dG(deoxyguanosine) and sperm density (r = -0.358, p = 0.004), and between 8-OHdG/dG and sperm number (r = -0.389, p = 0.01). The results indicate that endogenous oxidative DNA damage could affect sperm quality and subsequently increase the risk of genetic defects.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1997

Menstrual patterns of workers exposed to low levels of 2-ethoxyethylacetate (EGEEA).

The objectives of this study were to determine the exposure levels among workers who handle 2-ethoxyethylacetate (EGEEA) in the liquid crystal display (LCD) manufacturing industry and to study the menstrual patterns among the exposed workers compared to a referent group of workers. A total of 52 female exposed workers and 55 referents was studied. Detailed menstrual histories were obtained by personal interview using a structured questionnaire. All the exposed had individual 8-hour personal monitoring for EGEEA in the environment and start-of-shift and end-of-shift urine analysis for EGEEA concentration. The geometric mean end-of-shift urine EGEEA concentration was 0.16 mg/g creatinine. End-of-shift urine EGEEA was well correlated with the air concentration; r = 0.81 [p < 0.0001]. No significant differences were observed between the exposed and referent groups for duration of each menstrual cycle (period), duration (days) of the menses, and the amount of flow, even after adjusting for possible confounders viz. age, years of education, use of oral contraceptive pills, age at menarche, gravidity, and race. The workers in the LCD manufacturing industry were exposed to a mean TWA of 0.51 ppm of EGEEA. At this concentration, the findings did not reveal any significant difference between the menstrual patterns of the exposed and referent subjects.

Adult↗
PubMed1997

Endocrine profiles of male workers with exposure to trichloroethylene.

The objective of this study was to examine the endocrine profiles of a group of male workers chronically exposed to trichloroethylene (TCE) in an electronics factory. A total of 124 workers participated in a preliminary study, for which 85 satisfied the selection criteria and were recruited to take part in a more detailed study. Each of the 85 workers had urine collected and analyzed for trichloroacetic acids (TCA) on the day blood was taken for analysis of serum testosterone (T), follicle-stimulating hormone (FSH), dehydroepiandrosterone sulphate (DHEAS), and sex-hormone binding globulin (SHBG). Environmental TCE exposures were conducted for 12 workers. The geometric mean concentration of environmental TCE was 29.6 ppm (range 9-131) and the mean urine TCA was 22.4 mg/g creatinine (range 0.8-136.4). The results showed that years of exposure to TCE were significantly correlated with DHEAS and negatively correlated with SHBG and T levels. Serum FSH, T, and SHBG levels showed a gradual decline with increasing years of exposure to TCE. This dose-response decrease indicated that there was a disruption of peripheral endocrine function. This disruption could be a result of TCE-induced liver malfunction. The most dramatic change was that the increase in DHEAS concentration was associated with years of exposure to TCE, rising from 255 to 717.8 ng/ml for < 3 to > or = 7 years exposure, respectively. This evidence suggests that chronic exposure to TCE may also affect adrenal function. These findings, however, must be confirmed by further investigations.

Adult↗
PubMed1997

Cumulative blood lead levels and neurobehavioral test performance.

The current scientific literature provides inadequate evidence to conclude whether or not cumulative exposure to or absorption of lead adversely affects performance in neurobehavioral tests in adults. One of reasons for this controversy is the lack of studies with good cumulative exposure to or dose of lead. The aims of this study are to compare the neurobehavioral test performances of a group of lead-exposed workers and a referent group, and to study the association of the neurobehavioral test performances with concurrent blood lead levels and cumulative blood lead levels. Fifty lead battery workers and 97 non-exposed (referent) workers from a vehicle maintenance workshop were evaluated on their neurobehavioral performance using the World Health Organization Neurobehavioral Core Test Battery (WHO-NCTB). The geometric mean concurrent blood lead (ConPb) of the exposed and referent groups were 37.1 (range 13.2-64.6) microg/100 ml and 6.1 (range 2.4-12.4) microg/100 ml, respectively. Cumulative blood lead (CumPb) was defined as area under the curve for the number of years each worker was exposed to lead (three workers previous blood lead results were not available). ConPb and CumPb were used to study the association with the neurobehavioral test results. The exposed group had significantly poorer manual dexterity, perceptual-motor speed, and motor steadiness compared with the referents. The standardized partial regression coefficients were higher for CumPb than ConPb for most of the neurobehavioral test results. In the group >35 years old, there were significantly stronger associations between CumPb and Digit Symbol and Trail Making Part A results than for ConPb which are tests of perceptual and motor skills. CumPb was a better predictor than ConPb of the effects of lead on neurobehavioral performances.

Adult↗
PubMed1997

Sickness absence in private sector establishments in Singapore.

AIM: A study was conducted in June 1995 to determine the current level of sickness absence in Singapore. METHOD: The questionnaire survey was part of a larger labour market survey conducted quarterly by the Ministry of Labour, and covered 3,553 private sector establishments employing 25 or more employees. RESULTS: Overall, 14.4% of the 628,477 employees took sick leave, while the percentage of working days lost due to sick leave, excluding maternity leave, was 1.1%. An average of 3.2 days of medical leave were taken per person per year. Industry specific characteristics seemed to have more influence on sickness absence than establishment size, employee's sex and occupation (viz, professional versus clerical versus production staff), number of hours worked and overtime work. Over 60% of the establishments, particularly larger companies and those in manufacturing, implemented measures to control sickness absence, most commonly counselling, disciplinary procedures and attendance allowance or bonus. Over 13% monitored sickness absence using computerised records. CONCLUSION: Comparing with overseas sickness absence (lost time) rates, the rates observed in this study do not appear high.

Absenteeism↗
PubMed1997

Postural stability in non-insulin dependent diabetics.

Postural stability in 55 non-insulin dependent diabetics was compared with 53 non-diabetic controls matched for age and gender. The study was conducted in a primary care clinic, using a computerised postural sway system. Changes in the centre of pressure while the subjects stood on a force platform were recorded, and sway parameters computed using customised software. Clinical data were obtained by interview, physical examination, and from case records. Results of the study showed that non-insulin dependent diabetics were more unstable than the non-diabetic controls for four out of the six parameters studied (namely L, length of sway path; Vel, average speed of centre of pressure along its path; Ao, area included within the path of the centre of pressure; and Ae, 95% confidence elliptical area), after adjusting for height, weight, adequate sleep and alcohol intake the night before, and history of bone or thyroid disorders. Amongst diabetic subjects, significant factors associated with postural stability were age, weight, presence of peripheral neuropathy or cataract, metformin, use, and HbAlc levels > 9%. Further studies are indicated to look into factors affecting postural stability (other than diabetic neuropathy) in greater depth.

Adult↗
PubMed1996

Cumulative blood lead levels and nerve conduction parameters.

Most studies on the effects of lead on the peripheral nerves used "current' blood lead levels of the workers and infer the nerve conduction's findings to it. This practice is not ideal as the toxicity of lead on the peripheral nerves occurs over a period of time. Seventy-two workers in a lead battery manufacturing factory and 82 referents were studied with the aim of (1) correlating the nerve conduction parameters of the median and ulnar nerves of the dominant forearms with the blood cumulative lead-years (BPbCum) results; (2) determining a "noeffect' cumulative dose of lead on the peripheral nerves. The mean BPb for the exposed and referent were 36.9 micrograms/100ml and 10.5 micrograms/100ml, respectively. The mean BPbCum was 136.8 (range = 6.7-1087.0)micrograms-year/100ml. Significant differences were found in the adjusted (for age, ethnical groups, smoking and drinking habits by ANCOVA) means median sensory conduction velocity, motor conduction veloclty, distal latency and amplitude between the exposed and referent groups. But for the ulnar nerve only, distal latency was significantly different. With the BPbCum groups, dose response relations are noted in both the nerve conduction parameters of the median and ulnar nerves. There were no significant differences for the ulnar and median nerves conduction parameters between BPbCum < 40 micrograms-year/100ml group and referent. Based on the study's findings, it would suggest that a maintained blood lead level of less than 40micrograms/100ml for one year may not have significant effects on the median and ulnar nerves.

Action Potentials↗
PubMed1996

Cumulative concentrations of blood lead and postural stability.

OBJECTIVE: To study the association in a group of battery manufacturing workers between computerised postural sway parameters and present concentrations of blood lead (PPb), index of cumulative blood lead years (CBI), and cumulative blood lead at different years of exposure (CPbYs). METHODS: Postural stability was investigated with a computerised postural sway measurement system in 60 workers exposed to lead with exposure duration of 84 (range 3-366) months and in 60 control subjects. An index of CBIs in 55 workers (previous blood lead results of five workers were not available) and CPbYs were computed for each worker by calculating the area under the curve of concentrations of blood lead against time. RESULTS: The mean (SD) PPb was 36.0 (11.7) (range 6.4 to 64.5) micrograms/dl for the exposed workers and 6.3 (2.4) (range 3.1-10.9) micrograms/dl for the 14 randomly selected control subjects. Significant differences between groups for the postural sway parameters obtained when the eyes were closed were found for length of sway path (L); mean velocity of the centre of pressure along its path (Vel); area included within the path of the centre of pressure (Ao); 95% confidence elliptical area (Ae). The Romberg ratio (the relation between eyes closed and open) for the Vel, L, Ao, and Ae of the exposed group were also significantly different from those of the controls. The postural sway parameters (eyes closed) were not significantly correlated with PPb or CBI. However, the cumulative blood lead for the past two years before the postural sway assessment, CPbY2, was significantly correlated with all the postural sway parameters. CONCLUSION: The study showed that workers exposed to lead had significantly poorer postural stability than a control group. Lead may affect certain parts of the somatosensory system resulting in postural instability when the visual input is cut off. The CPbY2 was significantly positively correlated with most of the postural sway parameters. Effects of lead on postural stability may be related to recent increases in blood lead concentration among the exposed workers rather than to cumulative body burden.

Adult↗
PubMed1996

Three-year follow-up of serial nerve conduction among lead-exposed workers.

OBJECTIVES: The purpose of this study was to investigate the serial nerve conduction parameters of a group of lead-exposed workers and determine their correlation with the serial blood lead results over a three-year period. A "nonresponse" level (defined as no significant changes in the nerve conduction in response to changes in the blood lead level of each exposed worker observed over the period of study) was also determined for blood lead in respect to the peripheral nerves. METHODS: Seventy-two male workers from a lead battery manufacturing factory were followed at six-month intervals for three years. At each follow-up, the blood lead level was determined and nerve conduction tests (ulnar and median nerves) were conducted. A group of 82 unexposed subjects served as referents. RESULTS: Significant differences were observed for some of the mean values of the median nerve conduction parameters between the exposed and reference groups. The 28 exposed workers who completed the follow-up were divided into the following two blood lead categories: < 40 micrograms. 100 ml-1 (< 1.93 micromol.l-1 and > or = 40 micrograms. 100 ml-1 (> or = 1.93 micromol.l-1. In the latter, the median motor conduction velocity, median distal latency, median amplitude, ulnar motor conduction velocity, and ulnar amplitude were significantly correlated (adjusted for age and within-subject variation) with the blood lead levels, but not so in the former. CONCLUSIONS: According to the three-year serial results, the "nonresponse" level for blood lead with respect to the peripheral nerves would be < 40 micrograms.100 ml-1 (< 1.93 micromol. l-1).

Adult↗
PubMed1996

Review of published clinical trials conducted in Singapore from 1959 to 1994.

Trials are increasingly being used to evaluate the effectiveness of health care interventions. As has been recognised by those active in these activities, there is a need, not only to search for all published materials, but also to evaluate their quality and usefulness. This paper is an attempt to provide information and to examine the areas of focus and quality of information on all published clinical trials conducted in Singapore from 1959 to 1994. The searches were conducted using the MEDLINE CD-ROM for the period from 1966 to 1994 and manual search for the period before 1966. All published studies involving drugs or procedures (surgical techniques or instrumentation) on human subjects performed in Singapore were included in the study. Out of a total of 136 papers obtained, 90 fulfilled our criteria. There is an increase in the number of publications over the years especially in the last 10 years; with the biggest surge in the last 5 years. Most of the clinical trials were pharmacological intervention studies (57.8%) although there is a steady rise in non-pharmacological studies recently. As the number of clinical trials increases, coupled with the rising cost, it would be useful for the relevant authorities to consider setting up a registry to co-ordinate the trials that are being conducted.

Clinical Trials as Topic↗