Ethnicity influences the gut microbiota of individuals sharing a geographical location: a cross-sectional study from a middle-income country.

No studies have investigated the influence of ethnicity in a multi-ethnic middle-income country with a long-standing history of co-habitation. Stool samples from 214 Malaysian community members (46 Malay, 65 Chinese, 49 Indian, and 54 Jakun) were collected. The gut microbiota of the participants was investigated using 16S amplicon sequencing. Ethnicity exhibited the largest effect size across participants (PERMANOVA Pseudo-F = 4.24, R2 = 0.06, p = 0.001). Notably, the influence of ethnicity on the gut microbiota was retained even after controlling for all demographic, dietary factors and other covariates which were significantly associated with the gut microbiome (PERMANOVA Pseudo-F = 1.67, R2 = 0.02, p = 0.002). Our result suggested that lifestyle, dietary, and uncharacterized differences collectively drive the gut microbiota variation across ethnicity, making ethnicity a reliable proxy for both identified and unidentified lifestyle and dietary variation across ethnic groups from the same community.

Nitrogen dioxide exposure from domestic gas cooking and airway response in asthmatic women.

BACKGROUND: Previous studies have not found a consistent association between exposure to domestic cooking using gas appliances and exacerbation of asthma. We investigated the immediate airflow response to acute exposure from single episodes of gas cooking, and peak airflow variability from continued exposure to repeated episodes of gas cooking in a group of non-smoking asthmatic women. METHODS: Sixteen adult non-smoking women with mild to severe persistent asthma were studied. The acute short term level of nitrogen dioxide (NO2) during gas cooking episodes and the mean exposure to NO2 from repeated gas cooking episodes were measured over a 2 week period, as well as proxy measures of frequency of cooking on each day and the length of time spent cooking each day. Their asthma status was monitored using peak expiratory flow rates (PEFR) before and after cooking, 2 week self-recorded serial readings of PEFR, respiratory symptom severity score, and use of rescue bronchodilators for acute asthma attacks. RESULTS: Cooking was significantly associated with an immediate mean fall in PEFR of 3.4% (p=0.015, paired t test). The acute short term NO2 level during cooking was significantly correlated with the fall in PEFR (r=-0.579; p=0.019). The frequency of cooking over a 2 week period was positively correlated with the mean exposure to NO2 (r=0.529; p=0.042). Continued exposure to NO2 over a 2 week period was associated significantly with increased frequency of rescue bronchodilator usage for asthma attacks (r=0.597; p=0.031). However, it was negatively associated with PEFR variability (r=-0.512; p=0.051) and respiratory symptom severity score (r= -0.567; p=0.043), probably due to the masking effects of bronchodilator treatment. CONCLUSIONS: Acute short term exposure to NO2 from single episodes of gas cooking is associated with immediate airflow limitation. Continued exposure from repeated episodes of gas cooking in asthmatic women is associated with greater use of rescue bronchodilators.

A cross-sectional survey of physical activity among middle aged women in Singapore.

OBJECTIVES: To assess the extent to which middle-aged women in Singapore engage in physical activity of a level which would result in long-term health benefits, and to determine the factors associated with this. METHODS: We conducted a cross-sectional survey of women aged between 35 and 60 years residing in Marine Terrace. A standardised questionnaire incorporating a modified Seven-Day Recall Questionnaire was used to record the level and type of physical activity engaged in over the past week. Demographic information and factors promoting or discouraging sports and exercise were also elicited. The total energy expenditure for household, occupational and sports activities of moderate intensity and above was calculated using metabolic equivalents (METs) in kcal/kg/week. RESULTS: Of the 341 respondents, 50.7% reported engaging in at least moderate activity for 30 minutes or more every day during the past week, thus fulfilling the WHO recommendations on physical activity. Housework contributed significantly to the energy expenditure on these activities among our target population. After adjusting for age, body mass index and educational level, we found that housewives without domestic help were most likely to fulfill the WHO recommendations. Housewives or working women with domestic help were the two groups at highest risk of low physical activity. A lack of time was the reason most commonly cited for not engaging in sports or exercise. CONCLUSION: Studies assessing physical activity in relation to disease risk among women should include domestic work in addition to the traditional leisure-time activities. There is a scope for further efforts to improve the level of activity in this population, which could be facilitated by the support of health professionals, employers and family members.

Urinary 2/16 alpha-hydroxyestrone ratio: correlation with serum insulin-like growth factor binding protein-3 and a potential biomarker of breast cancer risk.

Metabolism of estradiol occurs via two mutually exclusive hydroxylative pathways, yielding metabolites of divergent biological properties. 2-hydroxyestrone (2OHE1) is anti-estrogenic while 16 alpha-hydroxyestrone (16 alpha OHE1) is a potent estrogen. The ratio of 2OHE1 to 16 alpha OHE1 (2/16 alpha-OHE1 ratio) represents the net in vivo estrogenic activity. In this study, we sought to determine if the urinary 2/16 alpha-OHE1 ratio could be a predictor of breast cancer risk and the factors which influence this ratio. Variables analysed included age at diagnosis, menopausal status, parity, use of oral contraceptives, body mass index, serum levels of insulin-like growth factor-I (IGF-I), IGF binding proteins (BPs) and the presence of breast cancer. Serum and urine were collected from 65 breast cancer patients and 36 controls after an overnight fast. Urinary estrogen metabolites were measured by enzyme immunoassays while serum levels of IGF-I, BP-1 and BP-3 were determined by immunoradiometric assays. 2OHE1 levels and 2/16 alpha-OHE1 ratios were significantly lower (P < 0.05) while 16 alpha OHE1 levels were higher (P < 0.01) in cancer patients. Multiple linear regression analysis showed that levels of urinary metabolites were influenced by parity and breast carcinoma. 2/16 alpha-OHE1 ratio correlated positively with serum BP-3 level (P = 0.03). By multiple logistic regression, 2/16 alpha-OHE1 ratio was the most significant factor predictive of breast cancer. The odds ratio for women with higher 2/16 alpha-OHE1 ratios was 0.10 (0.03-0.38, 95% confidence interval). In conclusion, the profile of urinary estradiol metabolites was distinctly altered in breast cancer patients. In addition, BP-3 may be a potential mechanism by which estradiol metabolites influence breast cancer progression. As 16 alpha OHE1 has been shown to initiate neoplastic transformation of mammary epithelial cells, the 2/16 alpha-OHE1 ratio may serve as a biomarker of increased risk of breast cancer.

Epidemiology of sick building syndrome and its associated risk factors in Singapore.

OBJECTIVES: To investigate the occurrence of sick building syndrome in a tropical city, and its relation to indoor air quality and other factors. METHODS: 2856 office workers in 56 randomly selected public and private sector buildings were surveyed. The study consisted of a self administered questionnaire assessing symptoms and perception of the physical and psychosocial environment, inspection of the building plans and premises, and measurement of temperature, relative humidity, respirable particles, chemicals, bioaerosols, and other variables. RESULTS: Symptoms typical of the sick building syndrome were reported in 19.6% of the respondents. Multivariate modelling substantiated contributions associated with low thermal comfort, high work related stress, too much noise, a history of allergy or other medical conditions, poor lighting, young employees, and female sex. Measurements of indoor air quality or ventilation were not found to be reliable predictors of the symptoms. CONCLUSION: The survey confirmed the presence of sick building syndrome and its risk factors in the tropics. A biopsychosocial approach to the problem involving symptomatic treatment, environmental control, good ergonomic design, and stress management is recommended.

Elements in the hair of South-east Asian islanders.

Mercury (Hg), lead (Pb), cadmium (Cd) and copper (Cu) in hair samples from Singapore island (85 samples) and two islands off Batam, Indonesia (68 samples) were analysed to assess the environmental uptake of elements. Hair samples were washed with 0.1% Triton X-100 solution for 20 min in an ultrasonic bath, rinsed five times with de-ionized water and air dried. Ten to 20 mg of hair samples were digested with 1 ml of ultra-pure concentrated nitric acid in Parr bombs at 120 degrees C for 2 h. Hair digests were analysed by atomic absorption spectrophotometry (AAS). Hg was determined by the cold vapour AAS method and Pb, Cd and Cu by the electro-thermal graphite furnace AAS method. For Singapore hair, the contents of Cd (in microgram/g) averaged 0.17 (range 0.02-1.81); Cu 13.2 (range 3.1-70.1); Hg 5.92 (range 1.14-35.52); and Pb 6.74 (range 0.06-107.8). For the islands off Batam, Cd was 0.32 (range 0.06-1.80); Cu 21.1 (range 3.8-143.6); Hg 5.59 (range 0.78-60.86); and Pb 15.1 (range 0.13-116.6). Statistically significant differences in Cd, Pb and Hg contents were observed between the hair samples from Singapore and those of the islands off Batam in cumulative logit analysis. Hair from Singapore contained more Hg, but less Cd and Pb compared to hair from the islands off Batam. For Pb in hair, significant differences were also observed between the two islands off Batam (island 1, 18.9; and island 2, 10.2). These differences in hair metal contents are due to differences in community lifestyle (dietary, environmental or occupational intake).

Effects of occupational exposure to toluene: a neuropsychological study on workers in Singapore.

The neuropsychological functionings of workers (n = 29) occupationally exposed to low level of toluene (mean blood toluene level 1.25 ug/ml, standard deviation [SD] 0.37 ug/ml) were assessed by a test battery based on the recommendation of US National Institute of Occupational Safety and Health. The data revealed that the exposed workers performed poorer than a control group (mean blood toluene level 0.16 ug/ml, SD 0.06 ug/ml) in short-term memory, sustained attention and concentration, visual scanning, perceptual-motor speed, and finger dexterity. Results of the study confirmed that exposure to toluene may result in different degree of impairments of brain functions.

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.

Serum DDT and DDE levels in Singapore general population.

A simple and fast method was used to determine 1,1'-(2,2,2-trichloroethylene)-bis(4-chlorobenzene) (DDT) and 1,1'-(2,2-dichloroethylidene)-bis(4-chlorobenzene) (DDE) in blood serum. Serum samples pre-treated with formic acid were extracted with n-hexane and determined by gas chromatography (GC-ECD), using PTE-5 capillary column. Detection limits for DDT and DDE were 0.5 ppb. Recovery with a fortified pooled sample at 1 ppb level was 107.0% for DDT and 106.0% for DDE. At 10 ppb level, the recoveries for DDT and DDE were 96.1% and 92.7%, respectively. Eighty-nine random blood samples collected from volunteers were analyzed. The geometric mean (GM) serum level of DDT was 1.9 ppb (0.2-8.9 ppb) and that of DDE was 10.8 ppb (1.5-88.1 ppb). There was a positive correlation between DDE and DDT level (r = 0.33, P < 0.01). The serum DDE level was positively correlated with age (r = 0.49, P < 0.01) and DDT x Age (r = 0.62, P < 0.01). No correlation was observed between DDT and age. These results suggest that DDE, a metabolite of DDT, is cumulative in the body. Therefore blood DDE could be used as a cumulative exposure marker for DDT, whereas blood DDT may be used to reflect its recent exposure.

Postural stability among manganese exposed workers.

Postural stability was investigated by static posturography in 32 manganese exposed workers with exposure duration of 6.6 (range 1.1-15.7) years and 53 referent subjects. The mean current urine manganese concentration for the exposed was 6.0 micrograms/g creatinine (range 0.6 to 53.3). There was no significant differences between both groups for the postural sway parameters obtained during eyes open condition. However, significant differences were observed for L - length of sway path and Vel - mean velocity of the center of pressure along its path. The Romberg Ratios (the relationship between eyes closed/open conditions) for the exposed's Vel, L, and Ao were also significantly different from the referent. The study showed that manganese exposed workers had significantly poorer postural stability compared to a referent group. We postulate that this could be a subclinical effect of manganese on the basal ganglia (pallidus) resulting in the postural instability when the visual input is cut off. Based on the current urinary manganese levels, we were not able to obtain any significant association with the postural sway parameters.

Postural stability of workers exposed to lead.

OBJECTIVE: To detect, with a computerised postural sway measurement system, any significant deviation of postural sway parameters among lead workers compared with a control group. METHODS: Postural stability was investigated with a computerised postural sway measurement system in 60 workers exposed to lead with a duration of exposure of 84 (range 3-366) months and 60 controls. Sway parameter data were collected with an Advanced Mechanical Technology computerised biomechanics platform system. RESULTS: The mean current blood lead concentration was 36.0 (range 6.4 to 64.5) micrograms/dl for the exposed workers and 6.3 (range 3.1 to 10.9) micrograms/dl for the 14 controls. There was no significant difference between the groups for the postural sway parameters obtained when the eyes were open. Significant differences were found for Xs, Ys (SDs of the coordinates of the centre of pressure); Xm, Ym (mean deviation of the coordinates of the centre of pressure); Rm (average displacement of Xi, Yi, from Xo, Yo); L (length of sway path); Vel (mean velocity of the centre of pressure along its path); Ao (area included within the path of the centre of pressure); Ae (95% confidence elliptical area). The Romberg ratios (the relation between eyes closed and open) for the Vel, L, Ao and Ae of the exposed workers were also significantly different from the controls. CONCLUSION: The study showed that workers exposed to lead had significantly poorer postural stability than the controls. Lead may affect certain parts of the whole sensory neural axis resulting in postural instability when the visual input is cut off. Based on current blood lead concentrations, we were not able to obtain any significant association with the postural sway parameters.

Chronic neurobehavioural effects in paint formulators exposed to solvents and noise.

Twenty-one male paint formulators with an average age of 41.3 years (range 27-53), educational level of 7.4 years (range 5-10) and exposure level of 0.09 times Threshold Limit Value (TLV) index of solvent mixture (range 0.003-0.24 times TLV-index) for 20.2 years (range 7-39) were studied with a battery of neurobehavioural performance tests including digit span, digit symbol, Benton visual retention, finger tapping, grooved peg board, and aiming test. A group of 21 male workers matched for age (mean 40.8 years, range 25-53) and education (mean 6.9 years, range 5-12), and with no history of exposure to neurotoxic agents were selected as controls. In all the neurobehavioural tests, the exposed workers' performances were observed to be poorer than the controls'. Statistically significant differences were observed in digit span, grooved peg board, and the Z score after adjusting for age, level of education and ethnicity. The least square means for digit span were 11.7 (standard error [SE] 0.77) and 9.2 (SE 0.79); for grooved peg board were 60.5 (SE 2.1) and 69.7 (SE 2.1); and for neurobehavioural Z score were 0.02 (SE 0.11) and 0.50 (SE 0.11) in the controls and exposed workers respectively. The exposed group also performed significantly poorer in aiming test error score and digit span when compared to the controls after adjusted for age, education and ethnicity. The least square means for aiming test error score were 6.5 (SE 2.7) and 12.8 (SE 2.8) for the controls and exposed workers respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sleep deprivation on performance of Naval seamen: I. Total sleep deprivation on performance.

Sleep deprivation leads to impairment in performance, loss of efficiency and deterioration in mood states such as tension, depression, aggression, fatigue, confusion and vigour. These can be detrimental to combat readiness and could contribute to "battle stress". In the present study, a homogeneous group of 20 seamen under total sleep deprivation was rated 6 hourly with the Stanford Sleepiness Scale (SSS), Profile of Mood States (POMS) and a battery of performance tests including the trail making, grooved peg board, digit span, digit symbol, sea-shore rhythm, flicker fusion, dynamometer and naval tasks. With the exception of the trail making test and naval tasks, the test performance was observed to correlate significantly (P < 0.05) with the SSS. A higher sleepiness score was associated with a poorer performance in test scores. On the time trends of sleep deprivation on the performance tests measured, a dip in performance was observed in all the tests at 42 hours of sleep deprivation and continuous deterioration of performance was observed after 72 hours of sleep deprivation. The cognitive, vigilance, mood and sleepiness tests were substantially affected by sleep deprivation. Greater effect was observed in tests that involved cognition, speed and precision and smaller effect was observed in routine tasks that involved gross manual movement. The decrease in performance observed at 42 hours of sleep deprivation was 5.9 standard deviation from initial values for SSS; 3.9 for sea-shore rhythm, 3.0 for grooved peg board; 2.6 for dynamometer; 2.4 for mood; 1.8 for digit span; 1.6 for trail making and digit symbol; 1.0 for naval tasks and addition; and 0.9 for flicker fusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sleep deprivation on naval seamen: II. Short recovery sleep on performance.

Twenty male naval volunteers, aged 18 to 20 years, with 12 to 14 years of education, underwent a total sleep deprivation experiment on board a Republic of Singapore Navy landing ship in the South China Sea for a period of 42-102 hours. The sleep group comprised eight volunteers who dropped out at the 44th-46th h of the experiment and were randomly assigned to a 2 or 4 h sleep regime. The rest served as sleep-deprived controls. Neurobehavioural performance tests, profile of mood state and the Stanford Sleepiness Scale were applied 6 hourly starting from 6.00 am on the first experimental day. No thresholds were observed in the performance of tests related to manual tasks and subjective feeling, including naval tasks, mood and sleepiness scale during the sleep deprivation experiment. However, thresholds were observed in the performance of tests requiring cognitive and perceptive skills, including the grooved peg board, trail making, sea-shore rhythm, addition, digit span, digit symbol, flicker fusion and dynamometer tests. Performances in these tests were observed to deteriorate only after approximately 30 h of sleep deprivation. The Z score for the non-threshold tests (Z-N) deteriorated from -0.01 at the start of the experiment to 1.25 at the 42nd h of the experiment just before the imposed sleep and improved to 0.81 at the 48th h of the experiment just after the imposed sleep; and the Z score for the threshold tests (Z-T) varied from -0.07 at the start to 0.49 just before sleep (at the 42nd h) and to continuously deteriorate to 0.83 just after sleep (at the 48th h).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of a computerized postural sway measurement system for assessing workers exposed to manganese.

1. Computerized postural sway measurement systems have been used recently in human physiology and pharmacology for determining postural stability, but their applicability for the assessment of the effects of exposure to neurotoxic agents is lacking. 2. We have examined the feasibility of using a computerized postural sway measurement system to assess the postural sway parameters of manganese exposed workers compared with a control group. 3. Sway parameter data were collected using a KISLTER multicomponent measuring platform (Type 9281B) connected to VICON motion analysis system for 13 exposed and 16 control subjects. 4. Significant differences in several of the sway parameters (Px, Py--mean distance (mm), from the centre of the platform along the X-axis [anterior-posterior movement] and Y-axis [lateral movement], respectively) between the exposed and control groups were observed even after adjustment for possible confounders. Computerized postural sway measurement system may be a useful method of assessing workers exposed to neurotoxic agents affecting posture.

Neurobehavioral functions among workers exposed to manganese ore.

The Neurobehavioral Core Test Battery of the World Health Organization was performed on 17 baggers (mean age 36.6 years) in a manganese ore milling plant and 17 referents (mean age 35.7 years). The baggers had a mean exposure period of 7.4 (range 1-14) years with a mean blood manganese concentration of 25.3 (range 15-92.5) micrograms.l-1 [0.46 (0.27-1.68) mumol.l-1]. Of the 37 symptoms related to the nervous system, 20 were more frequently reported by the exposed workers. No significant differences were noted between the nerve conduction of the median and ulnar nerves of the dominant forearm of the two groups. The exposed workers had significantly poorer motor speed, visual scanning, visuomotor coordination, visuomotor and response speed, and visuomotor coordination and steadiness. A clinical examination did not reveal any abnormality among the two groups. Hence a neurobehavioral test battery may be a more sensitive method than a clinical examination in detecting early changes in motor function among manganese-exposed workers.

Neurobehavioral effects in occupational chemical exposure.

Neurobehavioral effects in 30 female workers (aged 18-41, mean 25.6) exposed to an average of 341 mg/m3 (SD 100) toluene for an average of 5.7 years (SD 3.3) compared with 30 matched controls (aged 18-48, mean 25.1), 24 male workers (aged 18-32, mean 24.7) exposed to 268 mg/m3 (SD 185) toluene equivalent of mixed solvent (82.2% toluene, 12.3% ethyl acetate, and 5.5% methyl ethyl ketone) for 2.3 years (SD 3.0) compared with 24 matched controls (aged 17-31, mean 24.3), and 94 dentists (aged 24-49, mean 31.7) exposed to 0.017 mg/m3 (SD 0.009) of elemental mercury for 7.4 years (SD 5.3) compared with 54 referents (aged 23-50, mean 33.6) were studied. The Z score (made up of Digit Span, Symbols Digit, and Grooved Peg Board) for the workers exposed to toluene was 0.79, for workers exposed to mixed solvents was 0.38, and for the dentists exposed to mercury was 0.42. The Z score for each group of exposed subjects was statistically poorer than that for its controls. Neurobehavioral performance was statistically related to exposure intensity for the toluene-exposed workers and to years of exposure or dose (exposure intensity x years of exposure) for mixed solvent- and mercury-exposed subjects. The type of chemical species and pattern of exposure appear to influence whether the adverse effects will be cumulative.

Metals in hair as biological indices for exposure.

Hair samples from three groups of occupationally exposed subjects were analyzed for their lead (Pb), manganese (Mn) and mercury (Hg) contents. For lead (number of subjects, n = 209), the hair Pb ranged from 0.93 to 3527 micrograms/g (geometric mean, GM = 641) and blood Pb from 33.3 to 774 micrograms/l (GM = 341); for manganese (n = 38), the hair Mn ranged from 0.20 to 52.97 micrograms/g (GM = 2.66) and urine Mn ranged from 1.70 to 17.9 micrograms/l (GM = 5.56); and for mercury (n = 85), the hair Hg from 1.79 to 12.8 micrograms/g (GM = 5.09) and the blood Hg from 0.63 to 57.3 micrograms/l (GM = 10.9). The hair Pb was significantly (P < 0.0001) correlated to blood Pb (r = 0.85); the hair Mn to urinary Mn (r = 0.45); and the hair Hg to blood Hg (r = 0.53). The average metal content at the distal end was not significantly (P > 0.05) different from that of proximal end. The GM levels for the distal end were 223 micrograms/g (95% CI 152-347) and 2.26 (95% CI 0.97-5.29); and those for the proximal end were 186 (95% CI 97-261) and 1.18 (95% CI 0.54-2.58) for Pb and Mn respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentrations of heavy metals in maternal and umbilical cord blood.

Concentrations of lead, cadmium, methylmercury and total mercury were measured in maternal and umbilical cord blood using graphite atomic absorption spectrometry. Two essential metals, copper and zinc, were also determined using ion chromatography. Lead, copper and zinc were found to be lower in the cord blood whereas methylmercury and total mercury were higher in cord blood than in maternal blood. Little differences were noted for cadmium in maternal and cord blood. Significant positive correlations were observed between the concentrations in maternal and cord blood with regard to lead (correlation coefficient, r = 0.44), copper (r = 0.34), zinc (r = 0.29), methylmercury (r = 0.44) and total mercury (r = 0.58). These results suggest that, like essential metals, most heavy metals can move rather freely across the human placenta. The potential health effects of heavy metal transfer from mothers to young infants cannot be discounted.