Biomedical subjects
M R Sim
Publications and source records attributed to M R Sim.
Maternal contamination with dichlorodiphenyltrichloroethane and reproductive outcomes in an Australian population.
Persistent organochlorine pesticides, such as dichlorodiphenyltrichloroethane (DDT), are lipophilic environmental pollutants which accumulate in the food chain. These chemicals have long half-lives and can be detected in human milk, serum, and some other tissues. These chemicals have recently been under scrutiny for their possible health hazards such as cancer and reproductive outcomes including low birth weight. The aim of our study was to investigate whether mothers with a higher contamination of pesticides were different from mothers with low contamination in relation to their offspring's birth outcomes such as birth weight, small for gestation age, prematurity, head circumference, sex ratio, and previous miscarriage or still birth. We used data collected as part of a cross-sectional study of organochlorines in breast milk. This study did not show any association between low birth weight or small for gestation age and organochlorine contamination when comparing the higher to the low exposure group. Weak, significant correlations (-0.1) were detected between low birth weight and contamination levels of dichlorodiphenyldichloroethylene (DDE) only in female offspring. There was a decrease in the percentage of female offspring for all chemicals in the high-contamination group. The baby's head circumference increased as the mother's contamination increased but the adjusted difference in means was not significant. We did not see any association between either miscarriage or stillbirth in the mother's previous pregnancies or prematurity of the first live (recent) baby when comparing the higher to the low exposure mothers. The organochlorines DDT and DDE were not found to be associated with adverse birth outcomes in contaminated mothers in the range of contamination of our population (<7.5 mg/kg lipid in maternal milk), although there is weak evidence that sex ratio may be affected.
Health Watch exposure estimates: do they underestimate benzene exposure?
A nested case-control study found that the excess of leukemia, identified among the male members of the Health Watch cohort, was associated with benzene exposure. Exposure had been retrospectively estimated for each individual occupational history using an algorithm in a relational database. Benzene exposure measurements, supplied by Australian petroleum companies, were used to estimate exposure for specific tasks. The tasks carried out within each job, the products handled, and the technology used, were identified from structured interviews with contemporary colleagues. More than half of the subjects started work after 1965 and had an average exposure period of 20 years. Exposure was low; nearly 85% of the cumulative exposure estimates were at or below 10 ppm-years. Matched analyses showed that leukemia risk increased with increasing cumulative benzene exposures and with increasing exposure intensity of the highest-exposed job. Non-Hodgkin lymphoma and multiple myeloma were not associated with benzene exposure. A reanalysis reported here, showed that for the 7 leukemia case-sets with greater than 16 ppm-years cumulative exposure, the odds ratio was 51.9 (5.6-477) when compared to the 2 lowest exposed categories combined to form a new reference category. The addition of occasional high exposures, e.g. as a result of spillages, increased exposure for 25% of subjects but for most, the increase was less than 5% of total exposure. The addition of these exposures reduced the odds ratios. Cumulative exposures did not range as high as those in comparable studies; however, the recent nature of the cohort and local handling practices can explain these differences.
Biological dust exposure in the workplace is a risk factor for chronic obstructive pulmonary disease.
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality. Although the main risk factor is smoking, 15-19% of COPD even in smokers has been attributed to occupational exposures. The aim of this study was to investigate the association between occupational exposure and risk of COPD. METHODS: Participants were part of a cross sectional study of risk factors for COPD. A total of 1232 completed a detailed respiratory questionnaire, spirometric testing and measurement of gas transfer. Job histories were coded according to the International Standard Classification of Occupations. These codes were then used to establish occupational exposures using the ALOHA job exposure matrix. RESULTS: The prevalence of emphysema was 2.4%, chronic obstructive bronchitis 1.8%, and COPD 3.4%. Subjects ever exposed to biological dusts had an increased risk of chronic obstructive bronchitis (OR 3.19; 95% CI 1.27 to 7.97), emphysema (OR 3.18; 95% CI 1.41 to 7.13), and COPD (OR 2.70, 95% CI 1.39 to 5.23). These risks were higher in women than in men. For biological dust, the risk of emphysema and COPD was also significantly increased in both the duration of exposure categories, again in women but not in men. No significant increased risks for COPD were found for mineral dust (OR 1.13; 95% CI 0.57 to 2.27) or gases/fumes (OR 1.63; 95% CI 0.83 to 3.22). CONCLUSION: In this general population sample of adults, occupational exposures to biological dusts were associated with an increased risk of COPD which was higher in women. Preventive strategies should be aimed at reducing exposure to these agents in the workplace.
Psychological health of Australian veterans of the 1991 Gulf War: an assessment using the SF-12, GHQ-12 and PCL-S.
BACKGROUND: Elevated rates of psychological morbidity and symptomatology have been widely reported in 1991 Gulf War veterans. The present study used brief self-report instruments to compare the psychological health of Australian Gulf War veterans with that of a randomly sampled military comparison group. METHOD: The 12-item Short Form Health Survey (SF-12), 12-item General Health Questionnaire (GHQ-12), Posttraumatic Stress Disorder Checklist--Specific (PCL-S) and Military Service Experience (MSE) questionnaire were administered to 1424 male Australian Gulf War veterans and 1548 male Australian Defence Force members who were operational at the time of the Gulf War conflict, but were not deployed there. RESULTS: The Gulf War veterans exhibited poorer psychological health, as measured by the above three instruments, than the comparison group members. For Gulf War veterans, the number of stressful experiences, as measured by the MSE questionnaire, was correlated with scores on the three instruments. SF-12 mental health component summary scores and PCL-S caseness, but not GHQ-12 caseness, differed significantly between Gulf War veterans and comparison group members who had been on at least one active deployment. CONCLUSIONS: More than a decade after the 1991 Gulf War, Australian Gulf War veterans are exhibiting higher levels of current (past month) psychological ill-health, as measured using the GHQ-12 and PCL-S, as well as lower mental health status, as measured by the SF-12, than the comparison group. Although not a replacement for formal psychiatric diagnosis, instruments such as those above may aid in the assessment of veterans' psychological health.
Symptoms and medical conditions in Australian veterans of the 1991 Gulf War: relation to immunisations and other Gulf War exposures.
AIMS: To investigate whether Australian Gulf War veterans have a higher than expected prevalence of recent symptoms and medical conditions that were first diagnosed in the period following the 1991 Gulf War; and if so, whether these effects were associated with exposures and experiences that occurred in the Gulf War. METHODS: Cross-sectional study of 1456 Australian Gulf War veterans and a comparison group who were in operational units at the time of the Gulf War, but were not deployed to that conflict (n = 1588). A postal questionnaire was administered and the likelihood of the diagnosis of self-reported medical conditions was assessed and rated by a medical practitioner. RESULTS: Gulf War veterans had a higher prevalence of all self-reported health symptoms than the comparison group, and more of the Gulf War veterans had severe symptoms. Increased symptom reporting was associated with several exposures, including having more than 10 immunisations, pyridostigmine bromide tablets, anti-biological warfare tablets, pesticides, insect repellents, reportedly being in a chemical weapons area, and stressful military service experiences in a strong dose-response relation. Gulf War veterans reported psychological (particularly post-traumatic stress disorder), skin, eye, and sinus conditions first diagnosed in 1991 or later more commonly than the comparison group. Over 90% of medical conditions reported by both study groups were rated by a medical practitioner as having a high likelihood of diagnosis. CONCLUSION: More than 10 years after the 1991 Gulf War, Australian veterans self-report all symptoms and some medical conditions more commonly than the comparison group. Further analysis of the severity of symptoms and likelihood of the diagnosis of medical conditions suggested that these findings are not due to over-reporting or to participation bias.
The health of Australian veterans of the 1991 Gulf War: factor analysis of self-reported symptoms.
BACKGROUND: A recent report showed that Australian veterans of the 1991 Gulf War displayed a greater prevalence of a multitude of self-reported symptoms than a randomly sampled comparison group of military personnel who were eligible for deployment but were not deployed to the Gulf. AIMS: To investigate whether the pattern, rather than frequency, of symptom reporting in these Australian Gulf War veterans differed from that of the comparison group personnel. METHODS: Factor analysis was used to determine whether the co-occurrence of 62 symptoms in 1322 male Gulf War veterans can be explained by a number of underlying dimensions, called factors. The methodology was also applied to 1459 male comparison group subjects and the factor solutions of the two groups were compared. RESULTS: For the Gulf War veterans, a three factor solution displayed replicability and construct validity. The three factors were labelled as psycho-physiological distress, somatic distress, and arthro-neuromuscular distress, and were broadly similar to those described in previous studies of Gulf War veterans. A concordant three factor solution was also found for the comparison group subjects, with strong convergence of the factor loadings and factor scores across the two groups being displayed. CONCLUSION: Results did not display evidence of a unique pattern of self-reported symptoms among Gulf War veterans. Results also indicated that the differences between the groups lie in the degrees of expression of the three underlying factors, consistent with the well documented evidence of increased self-reported symptom prevalence in Gulf War veterans.
Respiratory health status of Australian veterans of the 1991 Gulf War and the effects of exposure to oil fire smoke and dust storms.
BACKGROUND: Since the 1991 Gulf War concerns have been raised about the effects on veterans' health of exposures to Kuwaiti oil fire smoke and to dust storms. METHODS: A cross sectional study compared 1456 Australian Gulf War veterans with a randomly sampled military comparison group (n = 1588). A postal questionnaire asked about respiratory conditions, exposures, medications, tobacco use, demographic characteristics, and military service details. During a medical assessment, spirometric tests and a physical examination were performed and a respiratory questionnaire was administered. RESULTS: The response rate for the Gulf War veteran group was 80.5% and for the comparison group 56.8%. Australian Gulf War veterans had a higher than expected prevalence of respiratory symptoms and respiratory conditions suggesting asthma (OR 1.4; 95% CI 1.1 to 1.9) and bronchitis first diagnosed since the Gulf War (OR 1.9; 95% CI 1.2 to 3.1) but did not have poorer lung function or more ventilatory abnormalities than the comparison group. Veterans who reported exposure to oil fire smoke had slightly poorer forced vital capacity (difference between means -0.10 l; 95% CI -0.18 to -0.03) and those exposed to dust storms had a slightly better peak expiratory flow rate (difference between means 12.0 l/min; 95% CI 0.6 to 23.4) than veterans who did not report exposure. Veterans who were in the Gulf at or after the start of the oil fires had more respiratory conditions suggesting asthma (OR 1.7; 95% CI 1.0 to 2.9) than those who completed their deployment before this time. CONCLUSIONS: Increased self-reporting of respiratory symptoms, asthma, and bronchitis by veterans was not reflected in poorer lung function. The findings do not suggest major long term sequelae of exposure to oil fire smoke or dust storms.
Respiratory symptoms and lung function in bauxite miners.
OBJECTIVES: To determine whether cumulative bauxite exposure is associated with respiratory symptoms or changes in lung function in a group of bauxite miners. METHODS: Current employees at three bauxite mines in Australia were invited to participate in a survey comprising: questionnaire on demographic details, respiratory symptoms, and work history; skin prick tests for four common aeroallergens; and spirometry. A task exposure matrix was constructed for bauxite exposure in all tasks in all jobs based on monitoring data. Data were examined for associations between cumulative bauxite exposure, and respiratory symptoms and lung function, by regression analyses. RESULTS: The participation rate was 86%. Self-reported work-related respiratory symptoms were reported by relatively few subjects (1.5%-11.8%). After adjustment for age and smoking no significant differences in the prevalence of respiratory symptoms were identified between subjects, in the quartiles of cumulative bauxite exposure distribution. The forced expiratory volume in I s (FEV1) of the exposed group was found to be significantly lower than that for the unexposed group. After adjustment for age, height, and smoking there were no statistically significant differences between quartiles in FEVI, forced vital capacity (FVC) and FEVl/FVC ratio. CONCLUSIONS: These data provide little evidence of a serious adverse effect on respiratory health associated with exposure to bauxite in an open-cut bauxite mine in present day conditions.
Skin irritation in users of brominated pools.
This study investigated adverse skin and eye effects in swimmers using pools with three different disinfection systems (chlorine, chlorine/ozone and bromine/ozone) and monitored water quality parameters that may be related to adverse health effects. A cross-sectional study of 770 children swimming in three school pools was carried out over a 4 week period in November 1994 using a postal questionnaire. Physico-chemical and bacteriological parameters of water quality were monitored on a weekly basis. Responses were obtained for 385 swimmers. Skin rashes with an onset less than 24 h after swimming in the school pool were reported by 4-8% of swimmers. Compared with the bromine/ozone pool, the odds ratio (OR) of having a rash that started less than 24 h after pool use was 1.91 (CI 0.71-5.10) for the chlorine pool and 1.88 (CI 0.61-5.81) for the chlorine/ozone pool. Adjustment for possible confounders made no significant differences to these results. Eye redness, itch or irritation was reported by 23-33% of swimmers and 24% of non-swimmers, and wearing swimming goggles had a protective effect (OR 0.40; CI 0.24, 0.65). Disinfectant levels were more consistently maintained in the pools with automatically controlled systems. The bromine disinfection system was not associated with a greater risk of the development of skin rashes than other disinfection systems, but the numbers were small, and need to be interpreted with caution.
Respiratory disorders and allergies in tea packers.
The aim of this study was to determine whether respiratory symptoms or cross-shift declines in lung function were related to occupational exposure to tea dust. A cross-sectional epidemiological study was conducted at a tea-packing plant. Subjects completed a questionnaire, spirometry before and after a full work shift, skin prick testing and venipuncture. Among the 83% of the workers at the site who participated, the prevalences of asthma, wheezing, hay fever and atopy were similar to the general population. Work-related nasal symptoms were more commonly reported by blenders and operators. There were six (3.2%) subjects with a cross-shift decline in the forced expiratory volume in 1 s of > 10%. Specific immunoglobulin E antibodies to black or chamomile tea were observed in 10 (5.6%) employees. As there was little evidence of specific allergic sensitization to the tea varieties tested, the excess of work-related respiratory and nasal symptoms probably represented non-specific irritation.
Respiratory symptoms and lung function in alumina refinery employees.
OBJECTIVES: Employees in alumina refineries are known to be exposed to a number of potential respiratory irritants, particularly caustic mist and bauxite and alumina dusts. To examine the prevalence of work related respiratory symptoms and lung function in alumina refinery employees and relate these to their jobs. METHODS: 2964 current employees of three alumina refineries in Western Australia were invited to participate in a cross sectional study, and 89% responded. Subjects were given a questionnaire on respiratory symptoms, smoking, and occupations with additional questions on temporal relations between respiratory symptoms and work. Forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) were measured with a rolling seal spirometer. Atopy was assessed with prick skin tests for common allergens. Associations between work and symptoms were assessed with Cox's regression to estimate prevalence ratios, and between work and lung function with linear regression. RESULTS: Work related wheeze, chest tightness, shortness of breath, and rhinitis were reported by 5.0%, 3.5%, 2.5%, and 9.5% of participants respectively. After adjustment for age, smoking, and atopy, most groups of production employees reported a greater prevalence of work related symptoms than did office employees. After adjustment for age, smoking, height, and atopy, subjects reporting work related wheeze, chest tightness, and shortness of breath had significantly lower mean levels of FEV(1) (186, 162, and 272 ml respectively) than subjects without these symptoms. Prevalence of most work related symptoms was higher at refinery 2 than at the other two refineries, but subjects at this refinery had an adjusted mean FEV(1) >60 ml higher than the others. Significant differences in FVC and FEV(1)/FVC ratio, but not FEV(1), were found between different process groups. CONCLUSIONS: There were significant differences in work related symptoms and lung function between process groups and refineries, but these were mostly not consistent. Undefined selection factors and underlying population differences may account for some of these findings but workplace exposures may also contribute. The differences identified between groups were unlikely to be clinically of note.
Risky business: health risk assessment and public health policy on environmental carcinogens.
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Stability of methacholine chloride solutions under different storage conditions over a 9 month period.
Methacholine chloride solutions, routinely used for testing bronchial hyperreactivity, have been shown to degrade over time. The data published addressing the optimal conditions for methacholine chloride storage are conflicting and incomplete. This study investigated the effects of a variety of conditions on the stability of methacholine chloride. Methacholine chloride, dissolved in phosphate buffered saline (PBS) or sodium chloride (NaCl) at 50 and 0.39 g x L(-1), was subjected to various light and temperature conditions for 9 months. Methacholine chloride degradation was determined by high performance liquid chromatography, and all solutions underwent bacterial and pH testing. By 9 months, all 50 g x L(-1) solutions of methacholine chloride had degraded by 65+/-0.8%. All 0.39 g x L(-1) solutions in NaCl had degraded by 11.0+/-0.33%. The 0.39 g x L(-1) solutions in PBS which had been frozen, refrigerated or stored at room temperature had degraded by 8.0%, 16.0+/-0.3% and 63.8+/-0.5%, respectively. The pH of methacholine chloride was 7.2 in PBS at 0.39 g x L(-1), 5.8 in PBS at 50 g x L(-1), 3.9 in NaCl at 0.39 and 2.7 in NaCl at 50 g x L(-1). Bacterial contamination was minimal. The results of this study demonstrate that methacholine chloride is more stable at the higher concentration. However, the pH of the more concentrated solutions of methacholine chloride in sodium chloride could cause bronchoconstriction in some subjects. We therefore recommend storing methacholine chloride at 50 g x L(-1) in phosphate-buffered saline.
An outbreak of pruritic skin lesions in a group of laboratory workers--a case report.
In May 1993, an outbreak of pruritic skin lesions occurred among a group of employees located in four laboratories in the basement of an office building. Medical interviews with the affected workers were performed and an industrial hygiene survey of the site was conducted. Workers commonly reported a pricking sensation on exposed skin. Four of the workers had small (< 5mm) erythematous papules on their forearms. Just prior to the outbreak, the installation of fibrous glass insulation had commenced in the mechanical rooms which provided air to the basement of the building. Because of the nature of the symptoms and the temporal relationship with the nearby insulation work, direct skin contact with fibrous glass fibres was thought to be the cause of the outbreak. The poorly maintained air handling unit supplying air to the laboratories probably contributed to this outbreak by inefficient filtering of the circulating air.
Monitoring chemical exposure using breast milk: a methodological review.
Retrospective exposure assessments are often a major weakness in environmental epidemiologic studies. Many environmentally important chemicals are persistent lipophilic compounds which partition into fat and breast milk. The analysis of these chemicals in breast milk provides a noninvasive means of collecting large volumes of a biologic fluid that correlates well with body burden. This may provide an integrated measure of cumulative absorption over several years which can be used to assess exposure in several different epidemiologic study designs. However, consideration of toxicokinetic principles in the study design is important in order to allow for maternal and other factors unrelated to exposure which may influence breast milk concentrations. These factors include maternal age, parity, maternal body weight, time of sampling during the lactation period, and fat content of the breast milk. Failure to use standardized entrance criteria and to allow for the above factors in the analysis and interpretation of the study results may lead to invalid conclusions regarding past exposures. Allowance must also be made for the restrictions on the sampling frame available in any epidemiologic study using breast milk analysis. Published studies to date often have had several methodological deficiencies. With the introduction of biologic specimen banks, breast milk collection and analysis should play an important role in future epidemiologic studies, especially those investigating health outcomes in infants.
Indoor air quality and sick buildings.
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A dentigerous cyst associated with an Angle Class II malocclusion.
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