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.

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.

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.

Benzene pollution from gasoline usage.

Local gasolines contain benzene ranging from 1.8 to 3.7% and their use can lead to significant exposure to benzene. Gasoline station attendants were found to be exposed to short-term exposure levels (STEL) of 0.064-179 ppm. Their 8-h time-weighted averaged (TWA) exposure ranged from 0.028 to 0.71 ppm. For motorcar service mechanics, TWA exposure levels ranged from 0.014 to 1.7 ppm. The exposure of drivers of gasoline delivery tankers ranged from 0.08 to 2.37 ppm for personal TWA exposure over the whole workshift. For local people not occupationally exposed to gasoline or other benzene-containing volatile chemicals, exposure from the ambient environment ranged from 0.0023 to 0.027 ppm. Gasoline usage also contributed to the contamination of surface water with benzene. Benzene levels in water samples taken from drains leading from gasoline stations were between 1.1 and 40.4 micrograms l-1.

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).

Mercury in scalp hair of healthy Singapore residents.

Two hundred and twenty-five hair samples (150 Chinese, 44 Malays and 31 Indians) from healthy residents not occupationally exposed to mercury were analyzed by cold vapour atomic absorption spectrophotometry to determine their total, inorganic and organic mercury levels. The arithmetic means of total mercury levels in hair were 6.1, 5.2 and 5.4 ppm for the Chinese, Malays and Indians, respectively. Factors contributing to the amount of mercury in hair, including consumption of fish and marine products, use of traditional ethnic medicines, artificial hair waving, age, sex and ethnicity were analyzed. Fish consumption, sex and ethnicity are factors found to contribute significantly (p less than 0.05) to mercury levels in hair.

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.

Atomic absorption spectrophotometric microdetermination of total mercury in undigested biological samples.

The influence of reaction time upon stannous (II) chloride as a reductant in the cold-vapor atomic absorption spectrophotometric method was investigated. In this comparative study, virtually all operating conditions, including volumes and chemicals used, were made identical except for the redesigning of the reaction vessels. The use of a reaction mixing time of 2 minutes (TR method), rather than immediate bubbling with aspiration (IL method) of total mercury from undigested biological samples, has several advantages. There is an average 4.5-fold increase in sensitivity of peak height readings with virtually no loss of mercury vapor from the reaction vessel by diffusion. Using the TR method also eliminated interaction of mercury with the matrices investigated, viz., undigested blood, undigested saliva, undigested urine, and digested hair samples. The average recovery for the TR method was superior to the IL method, 99.3 +/- 3.2% vs. 84.7 +/- 3.3%, p less than 0.05. In addition, mercury concentrations determined with the TR method were identical using either peak area or peak height readings. It was also found that concentrations determined using either the formulae given by Magos and Clarkson (4) and Farant et al. (5) or an aqueous calibration curve were equivalent. Only 0.2-1.0 mL of biological samples was needed for each analysis in the study.

Medical students' exposure to formaldehyde in a gross anatomy dissection laboratory.

The authors studied 150 first-year medical students exposed to formaldehyde during the dissection of cadavers in a gross anatomy laboratory. As a reference group, they used 189 third- and fourth-year medical students matched for sex, ethnic group, and age. Environmental and personal samples were collected to determine the exposure to formaldehyde among the first-year students. The mean concentration of formaldehyde in parts per million (ppm) in the area was 0.50 ppm (range = 0.40-0.60 ppm) and the personal sample was 0.74 ppm (range = 0.41-1.20 ppm). No significant differences were noted in the pre- and post-exposure mean FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) among the 22 randomly selected exposed male and female subjects. Significant differences, however, were observed in the exposed group for symptoms of decreased ability to smell, eye irritation, throat irritation, and dry mouth in comparison with the reference group. These symptoms were also significantly related to the time and place of occurrence. Medical schools should take more concrete measures to reduce students' exposure to formaldehyde. Meanwhile, although it is not now the practice in most medical schools, students should have ready access to goggles and respirators when working in dissection laboratories.

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.

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.

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)

An epidemiological study of lung functions and hearing acuity in Singapore firemen.

This study was conducted on 506 firemen in Singapore. Interviews, pulmonary function tests and audiometry were conducted. With regard to pulmonary function, the results showed that forced vital capacity (FVC) increased up to the age of 25-30 years for both Chinese and Malays. Both FVC and forced expiratory volume in one second (FEV1.0) increased with standing height over the whole age range studied. The mean values of FVC and FEV1.0 were higher in Chinese. It was also found that the FEV1 of the subjects in the study showed a greater decline in rate with age than other workers studied by the authors previously. The hearing threshold of 83 fire fighters showed a prominent upward shift of 6-8 KHz at ages 20-30. This upward shift was more pronounced in the right ear. The implications of the findings are discussed and a comparison with results of other similar studies in other countries is made.

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)

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.

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)

Ventilatory function among metal workers in Singapore.

The ventilatory function of 634 workers in small scale metal working industries was evaluated. Almost five percent (4.7%) of the workers were found to have FEV1.0/FVC ratio of less than 75%. Compared with the lung function of industrial workers reported by Zee, 10.9% were found to have low ventilatory function. Comparison of the ventilatory function obtained from the metal workers with those of occupational groups previously reported shows that the metal workers have lower FVC and FEV1.0 values. Mid and end expiratory flow rates were also measured. These measures have been shown to be very sensitive in detecting obstructions in small airways. It is recommended that future studies should be carried out to obtain ventilatory functions for the normal population. The values reported here of FEV25%-75% and FEF75%-85% would be useful for future investigations in forced expiratory flow rates.