Musculoskeletal disorders of the neck and upper limb among sewing machine operators: A clinical investigation

One hundred and seven women participated in a clinical study of an age-stratified random sample of sewing machine operators compared to a group of auxiliary nurses and home helpers. Four groups, according to years of being a sewing machine operator, consisted of: (controls) 25; (0–7 years) 21; (8–15 years) 25; and (more than 15 years) 36. The numbers of the main clinical diagnoses in the four groups were: cervicobrachial fibromyalgia (myofascial pain syndrome) 2, 4, 11, 24; cervical syndrome 0, 1, 3, 10; and rotator cuff syndrome 1, 1, 6, 11. The observed exposure-response relationship between clinical outcomes and years as a sewing machine operator was maintained when adjusting for current exposure to musculoskeletal strain and other potential confounders. Muscle palpation proved to be a reproducible examination with kappa values around 0.70. © 1993 Wiley-Liss, Inc.     

Effects of drop out in a longitudinal study of musculoskeletal disorders

OBJECTIVES—The drop out rates in different longitudinal studies of musculoskeletal disorders range between 7% and 57%, and little is known about the characteristics of the subjects who dropped out. The aim was to analyse various consequences of drop out in a longitudinal study of musculoskeletal disorders and occupational risk factors during 1969-97.
METHOD—Data about occupational conditions and health in 1969 and in 1993 were analysed. Differences between those who participated throughout (participants) and drop out subjects in these analyses formed the basis for recalculations of earlier reported analyses of associations between occupational conditions and low back pain. In the recalculation the data were weighted to compensate for the differences.
RESULTS—More female and male drop out subjects than participants in 1993 had monotonous work, fewer women and more male drop out subjects had heavy lifting in 1969. In 1997, more female and male drop out subjects had had heavy lifting and low stimulation at work in 1993. At both occasions, there were differences between the drop out subjects and participants in occurrence of musculoskeletal disorders. The weighted analyses resulted in changes in risk ratio of 0.1-0.2.
CONCLUSIONS—Differences in occupational conditions and health among participants and drop out subjects in a longitudinal study of musculoskeletal disorders and occupational risk factors during 1969-97 did not markedly influence the risk ratios.


Keywords: panel study; non-response; survey method; methodological study     

Longitudinal study on work related and individual risk factors affecting radiating neck pain

OBJECTIVES—To study the effects of work related and individual factors affecting radiating neck pain.
METHODS—A longitudinal study was carried out with repeated measurements. A total of 5180 Finnish forest industry workers replied to a questionnaire survey in 1992 (response rate 75%). Response rates to follow up questionnaires in 1993, 1994, and 1995 were 83%, 77%, and 90%, respectively. The outcome variable was the number of days with radiating neck pain during the preceding 12 months with three levels (<8, 8-30, >30 days). The generalised estimating equations method was used to fit a marginal model and a transition model was used in a predictive analysis.
RESULTS—Items showing associations with radiating neck pain in both analyses were sex, age, body mass index, smoking, duration of work with a hand above shoulder level, mental stress, and other musculoskeletal pains. In the transition model, radiating neck pain in a previous questionnaire was included in the model. Although it was a strong predictor, the variables already mentioned retained their significance.
CONCLUSION—Programmes targeted to reduce physical load at work, mental stress, being overweight, and smoking could potentially prevent radiating neck pain.


Keywords: neck disorder; mental stress; physical work load     

A prospective study of work related factors and physical exercise as predictors of shoulder pain

OBJECTIVES—To evaluate the effects of work related and individual factors as well as physical activity and sports on the incidence and persistence of shoulder pain among forestry workers.
METHODS—Workers in a large Finnish forestry company replied to a questionnaire (a modified version of the Nordic questionnaire) on musculoskeletal pain and its possible risk factors for 4 consecutive years 1992-5. This 1 year follow up study covers the time 1994-5. Year 1994 was chosen as baseline because in that year the questionnaire contained for the first time more detailed questions about different sports. The response rate in 1995 was 90%. The effects of the predictors on 1 year incidence and persistence of shoulder pain were studied with multivariate logistic regression modelling.
RESULTS—At baseline, 2094 subjects had been free of shoulder pain during the preceding 12 months. After 1 year, 14% (n=285) reported having mild or severe shoulder pain. Higher age, obesity, and mental stress as well as physically strenuous work and working with trunk forward flexed or with a hand above shoulder level increased the risk of incident shoulder pain. Of the different sports activities, dancing increased the risk of incident pain whereas jogging decreased the risk significantly. Of those 419 workers who had severe shoulder pain at baseline, 55% (n=230) still had severe pain 1 year later. Higher age, overload at work, and working with a hand above shoulder level increased the risk of persistent severe shoulder pain whereas cross country skiing and general sports activity decreased the risk.
CONCLUSION—Our results support the current view that shoulder pain is the result of many factors, including occupational and individual factors. In this longitudinal study, physical work with a heavy load, awkward work postures, mental stress, and obesity were the risk factors at which preventive measures could be aimed. As a new finding, physical exercise had more protective than impairing effects on the shoulders.


Keywords: mental stress; physical work load; sports     

Interrelations of risk factors and low back pain in scaffolders

OBJECTIVES—To assess with a cross sectional study the interrelations between physical, psychosocial, and individual risk factors and different end points of low back pain.
METHODS—In total, 229 scaffolders and 59 supervisors completed a questionnaire about manual handling of materials, awkward back posture, strenuous arm position, perceived exertion, psychosocial load, need for recovery, and general health. Physical load at the worksite was also measured with many frequent observations. Interrelations between risk factors and their relation with four end points of low back pain were investigated.
RESULTS—Interrelations were strong among self reported determinants of physical load but showed an inverted trend for both age and total working experience, which could indicate the presence of a healthy worker effect. Weak relations existed between variables of psychosocial and physical load. The multivariate analyses showed a significant relation between high manual handling of materials, moderate perceived general health, high job demands, and low back pain in the past 12 months. Chronic low back pain was significantly correlated with high perceived exertion and moderate perceived general health. Severe low back pain was significantly correlated with awkward back postures, high need for recovery, and high job demands. Finally, low back pain with perceived disability was significantly related to strenuous shoulder positions and moderate perceived general health. All end points of low back pain were consistently associated with physical load whereas psychosocial aspects showed a more diverse pattern.
CONCLUSIONS—The findings of this study suggest that work related risk factors may vary according to different definitions of low back pain. Distinct patterns of risk factors might enhance different expressions of it. Scaffolders are a group at high risk of developing persistent forms of low back pain.


Keywords: interrelations; low back pain; risk factors     

Organisational downsizing and musculoskeletal problems in employees: a prospective study

OBJECTIVES—To study the association between organisational downsizing and subsequent musculoskeletal problems in employees and to determine the association with changes in psychosocial and behavioural risk factors.
METHODS—Participants were 764 municipal employees working in Raisio, Finland before and after an organisational downsizing carried out between 1991 and 1993. The outcome measures were self reports of severity and sites of musculoskeletal pain at the end of 1993 and medically certified musculoskeletal sickness absence for 1993-5. The contribution of changes in psychosocial work characteristics and health related behaviour between the 1990 and 1993 surveys was assessed by adjustment.
RESULTS—After adjustment for age, sex, and income, the odds ratio (OR) for severe musculoskeletal pain between major and minor downsizing and the corresponding rate ratios for musculoskeletal sickness absence were 2.59 (95% confidence interval (95% CI) 1.5 to 4.5) and 5.50 (3.6 to 7.6), respectively. Differences between the mean number of sites of pain after major and minor downsizing was 0.99 (0.4 to 1.6). The largest contribution from changes in work characteristics and health related behaviour to the association between downsizing and musculoskeletal problems was from increases in physical demands, particularly in women and low income employees. Additional contributory factors were reduction of skill discretion (relative to musculoskeletal pain) and job insecurity. The results were little different when analyses were confined to initially healthy participants.
CONCLUSIONS—Downsizing is a risk factor for musculoskeletal problems among those who remain in employment. Much of this risk is attributable to increased physical demands, but adverse changes in other psychosocial factors may also play a part.


Keywords: ocupational health; musculoskeletal disorders; downsizing     

The role of physical and psychological factors in occupational low back pain: a prospective cohort study

OBJECTIVE—To examine risk factors for onset of low back pain (LBP) in healthcare workers.
METHODS—Nursing students, during their 3 year training period, and 1 year after training were studied in a prospective cohort study, with repeated self reported measurements of determinants of LBP at 6 monthly intervals for 3 years during training, and after a 12 month interval there was an additional final follow up.
RESULTS—During training, increased risk of new episodes of LBP was associated with having had LBP at baseline, with part time work, and with a high score on the general health questionnaire (GHQ). A high GHQ score preceded the onset of LBP, in such a way that a high score at the immediately previous follow up increased risk of LBP at the next follow up. 12 Months after training, a history of recurring LBP during training increased the risk of a new episode as did having obtained work as a nurse. A high GHQ score at this follow up was also associated with a concurrently increased risk. Pre-existing GHQ score, either at the end of training or at baseline, had no effect on risk of LBP 12 months after training.
CONCLUSIONS—Other than a history of LBP, pre-existing psychological distress was the only factor found to have a pre-existing influence on new episodes of LBP. Increased levels of psychological distress (as measured by the GHQ) preceded the occurrence of new episodes of pain by only short intervening periods, implying a role for acute distress in the onset of the disorder. This finding suggests that management of the onset of occupational LBP may be improved by management of psychological distress.


Keywords: low back pain; nurses; psychological factors     

Short term influence of mechanical factors on regional musculoskeletal pain: a study of new workers from 12 occupational groups

OBJECTIVES—To determine the influence of short term exposure to mechanical factors on regional musculoskeletal pain.
METHODS—Full time newly employed workers were recruited from 12 occupational groups and information collected by questionnaire. Subjects indicated on a blank body manikin any low back, shoulder, wrist or forearm or both, or knee pain which had occurred during the past month and had lasted more than 1 day. Data were also collected with a previously validated questionnaire on working postures, manual handling activities, and repetitive movements of the upper limb. The relations between mechanical factors and each area of pain were calculated as odds ratios (ORs) with 95% confidence intervals (95% CIs). Adjustment was made for age and sex.
RESULTS—1081 subjects (median age 23; interquartile range 20-27) were recruited to the study (a participation rate of 91%). 261 (24%) reported low back pain, 221 (20%) shoulder pain, 93 (9%) wrist or forearm pain, and 222 (21%) knee pain. Several specific manual handling activities were found to be associated with low back, shoulder, and knee pain. Carrying weights of more than 50 lbs (23 kg) on one shoulder was the factor which was most strongly associated with low back pain (OR 2.4 (95% CI 1.5 to 3.8)), shoulder pain (OR 3.1 (95% CI 1.9 to 4.8)), and knee pain (OR 3.5 (95% CI 2.2 to 5.5)), whereas forearm pain was most strongly associated with repetitive movements of the wrists (OR 1.8 (95% CI 1.04 to 3.1)). By contrast very few postures were associated with regional pain, although bending forwards in an uncomfortable position for at least 15 minutes was associated with shoulder pain (OR 1.6 (95% CI 1.2 to 2.2)) and kneeling for at least 15 minutes was associated with knee pain (OR 1.8 (95% CI 1.2 to 2.6)). Exposure to mechanical factors was most strongly associated with pain at multiple sites rather than with pains in individual regions.
CONCLUSIONS—Even among workers with only short term exposure to mechanical factors, musculoskeletal pain is increased.


Keywords: epidemiology; manual handling; questionnaire     

Prospective study of hepatic, renal, and haematological surveillance in hazardous materials firefighters

OBJECTIVES—To evaluate possible health effects related to work with hazardous materials as measured by end organ effect markers in a large cohort over about 2 years, and in a subcohort over 5 years.
METHODS—Hepatic, renal, and haematological variables were analysed from 1996-98 in hazardous materials firefighters including 288 hazardous materials technicians (81%) and 68 support workers (19%). The same end organ effect markers in a subcohort of the technicians were also analysed (n=35) from 1993-98. Support workers were considered as controls because they are also firefighters, but had a low potential exposure to hazardous materials.
RESULTS—During the study period, no serious injuries or exposures were reported. For the end organ effect markers studied, no significant differences were found between technicians and support workers at either year 1 or year 3. After adjustment for a change in laboratory, no significant longitudinal changes were found within groups for any of the markers except for creatinine which decreased for both technicians (p<0.001) and controls (p<0.01).
CONCLUSIONS—Health effects related to work are infrequent among hazardous materials technicians. Haematological, hepatic, and renal testing is not required on an annual basis and has limited use in detecting health effects in hazardous materials technicians.


Keywords: hazardous materials; firefighters; medical surveillance     

Are neck flexion,neck rotation,and sitting at work risk factors for neck pain? Results of a prospective cohort study

OBJECTIVE—To study the relation between neck pain and work related neck flexion, neck rotation, and sitting.
METHODS—A prospective cohort study was performed with a follow up of 3 years among 1334 workers from 34 companies. Work related physical load was assessed by analysing objectively measured exposure data (video recordings) of neck flexion, neck rotation, and sitting posture. Neck pain was assessed by a questionnaire. Adjustments were made for various physical factors that were related or not related to work, psychosocial factors, and individual characteristics.
RESULTS—A significant positive relation was found between the percentage of the working time in a sitting position and neck pain, implying an increased risk of neck pain for workers who were sitting for more than 95% of the working time (crude relative risk (RR) 2.01, 95% confidence interval (95% CI) 1.04 to 3.88; adjusted RR 2.34, 95% CI 1.05 to 5.21). A trend for a positive relation between neck flexion and neck pain was found, suggesting an increased risk of neck pain for people working with the neck at a minimum of 20° of flexion for more than 70% of the working time (crude RR 2.01, 95% CI 0.98 to 4.11; adjusted RR 1.63, 95% CI 0.70 to 3.82). No clear relation was found between neck rotation and neck pain.
CONCLUSION—Sitting at work for more than 95% of the working time seems to be a risk factor for neck pain and there is a trend for a positive relation between neck flexion and neck pain. No clear relation was found between neck rotation and neck pain.


Keywords: neck pain; physical risk factors; longitudinal cohort study     

Quantitative thermal perception thresholds relative to exposure to vibration

OBJECTIVES—To assess the risk of disturbed thermal perception relative to exposure to vibration, to investigate a possible exposure-response relation and to analyse a possible relation between thermal perception and sensory symptoms.
METHODS—The study was based on a cross section of 123 male workers exposed to vibration and 62 male workers who were not exposed. Thermal perception of cold, warmth, and heat pain was bilaterally determined from the thenar eminence by the method of limits. Perception of cold and warmth were also tested in the second digit. Personal energy equivalent exposure to vibration was measured for all subjects. Vibration was measured in accordance with International Standards Organisation (ISO) 5349 and assessed separately for the left and right hand.
RESULTS—Combining exposure times and intensities gave the left hand an 0.80 exposure to vibration compared with the right. The risk of having contracted reduced thermal perception was increased at all test sites. The risk was higher for the thenar measurements than the finger measurements. A yearly extra contribution of 4000 mh/s² in cumulative exposure increases the risk of contracting a wider neutral zone by 18% (95% confidence interval (95% CI) 1.06 to 1.32) for the right and 18% (1.05 to 1.32) for the left hand side. Subjects with symptoms of nocturnal paraesthesia had a rate ratio (95% CI) of 2.80 (1.17 to 6.67) for the right hand and 2.72 (1.12 to 6.63) for the left hand for increased neutral zones at the thenar eminence.
CONCLUSIONS—The results indicate thermal sensory impairment related to cumulative exposure to vibration. The effect appeared at vibration levels below the current guiding standard. Quantitative sensory testing of thermal perception offers the chance to assess this specific hazard to the peripheral sensorineural system associated with hand intensive work entailing vibration.


Keywords: quantitative thermal perception; heat pain; vibration; temperature threshold     

Prospective study of work related respiratory symptoms in trainee bakers

OBJECTIVES—To investigate the occurrence of work related respiratory symptoms and to assess the effect of atopy in a group of trainee bakers.
METHODS—A prospective study of work related respiratory symptoms among 125 trainee bakers who were investigated with a questionnaire plus skin prick test with wheat flour and α-amylase allergens at baseline and then after 6, 18, and 30 months.
RESULTS—At the baseline examination, four students (3.2%) complained of respiratory symptoms (cough and rhinitis) when working with flours and four were skin positive to wheat flour or α-amylase. The incidence of work related respiratory symptoms was 3.4% at 6 months, and the cumulative incidence was 4.8% and 9.0% at 18 and 30 months, respectively. The incidence of skin sensitisation to occupational allergens was 4.6% at 6 months and the cumulative incidence was 4.6% at 18 months and 10.1% at 30 months. The generalised estimating equation approach to longitudinal data showed that work related respiratory symptoms in the study population was significantly associated with a personal history of allergic disease (odds ratio (OR) 5.8, 95% confidence interval (95% CI) 1.8 to 18.2) and skin sensitisation to wheat flour or α-amylase (OR 4.3, 95% CI 1.2 to 14.9). Atopy based on prick test was not related to the occurrence of work related respiratory symptoms over time (OR 1.1, 95% CI 0.3 to 3.8).
CONCLUSIONS—Personal history of allergic disease is a predisposing factor for the development of symptoms caused by exposure to wheat flour and may be a criterion of unsuitability for starting a career as a baker. Atopy based on the skin prick test is useful for identifying subjects with allergic disease, but should not be used to exclude non-symptomatic atopic people from bakery work.


Keywords: follow up study; wheat flour; α-amylase sensitisation; work related respiratory symptoms     

Ultrasound Imaging for Tailored Treatment of Patients With Acute Shoulder Pain

PURPOSEThe objective of this study was to assess the frequencies of ultrasound findings in patients with acute rotator cuff disorders in family medicine.METHODSIn a prospective observational study, 129 patients aged 18 to 65 years with acute shoulder pain in whom the family physician suspected rotator cuff disease underwent ultrasound imaging.RESULTSRotator cuff disease was present in 81% of the patients, and 50% of them had multiple disorders. Calcific tendonitis was the most frequently diagnosed specific disorder. An age of 40 years or older was most strongly related to rotator cuff disease.CONCLUSIONSUltrasound imaging enables family physicians to rationalize treatment in nearly all patients who are aged 40 years and older with acute shoulder pain.     

Cross sectional study of a workforce exposed to hand-arm vibration: with objective tests and the Stockholm workshop scales

OBJECTIVES—Medical surveillance of workforces exposed to vibration has been recommended with the Stockholm workshop scales. The aims of this study were (a) to evaluate how the results of the objective tests individually and jointly associated with the final Stockholm workshop staging, (b) how this staging related to the history of exposure to vibration, and (c) how different trades were affected by the hazards from vibrating tools.
METHODS—All workers exposed to vibration in a heavy engineering company were examined with a questionnaire and a battery of tests. An assessment of staging by the Stockholm workshop scales was made. Estimates of the daily exposure and lifetime dosage of vibration of the various trades were reached.
RESULTS—The average years of tool use was 23.3 years (range 3-47 years) and the mean lifetime exposure was 11 022 (range 1012-46 125) hours. The individual neurological tests were all strongly associated with the Stockholm neurological staging but the cold provocation test was not associated with the Stockholm vascular staging. Neurological staging was significantly associated with age, years of tool use, and total hours of exposure to vibration, but not with trade or smoking. Vascular staging was significantly associated with age, years of tool use, total hours of exposure to vibration, and trade, but not with smoking. The mean neurological latent period was 19.7 (range 2-40) years and for the vascular component 19.1 (range 2-40) years. These means varied significantly by trade. The overall prevalence of neurological findings of 62% was greater than the overall prevalence of vascular findings, which was 33%.
CONCLUSIONS—(1) The neurological objective tests were found to be of use in neurological staging. The cold provocation test was not associated with the vascular staging and therefore was of little value. (2) Years of tool use was the exposure variable most significantly associated with evidence of damage to neurological component while years of tool use and trade were the variables most associated with vascular damage. (3) The prevalence of neurological symptoms (62%) was greater than the prevalence of vascular symptoms (33%). (4) Dressers and welders have shorter latent periods than platers and fitters.


Keywords: hand-arm vibration syndrome; neurological objective tests     

Nasal, eye, and skin irritation in dockyard painters

OBJECTIVES—To determine whether the risk of irritant symptoms in painters is related to their exposure to paint.
METHODS—The prevalences of skin, eye and nasal symptoms were compared in 260 United Kingdom and 109 Chinese dockyard painters, 539 British community controls, and 255 Chinese dockyard controls, relative to their exposure to paints.
RESULTS—Painters showed an excess of irritant symptoms compared with controls. Adjusted relative risks (RRs) (95% confidence interval (95% CI) were: for skin irritation 1.58 (1.19 to 2.08) in British painters and 2.68 (1.73 to 4.09) in Chinese painters; for eye irritation, 1.41 (0.98 to 2.05) and 3.01 (1.90 to 4.76); and for nasal irritation, 1.53 (1.10 to 2.14) and 6.73 (3.53 to 12.82), respectively. Exposure duration-response relations were found for these symptoms; the risks decreased with time after exposure ended.
CONCLUSIONS—Irritant symptoms occur more often in dockyard painters than in controls, and this is likely to be a response to exposure to paint.


Keywords: paint exposures; dockyard painting; health effect; irritant symptoms     

Symptoms, airway responsiveness, and exposure to dust in beech and oak wood workers

OBJECTIVES—To investigate the relation between levels of cumulative exposure to wood dust and respiratory symptoms and the occurrence of bronchial hyperresponsiveness among beech and oak workers.
METHODS—114 Male woodworkers from five furniture factories and 13 male unexposed controls were examined. The unexposed control group was supplemented by 200 male historical controls. Statistical analyses were performed excluding and including the historical controls. Dust concentration was measured by personal sampling methods. Cumulative exposure to dust was calculated for each woodworker by multiplying the duration of the work by the intensity of exposure (years.mg/m³). Bronchial hyperresponsiveness was assessed by the methacholine bronchial challenge test. Subjects were labelled methacholine bronchial challenge positive if forced expiratory volume in 1 second (FEV₁) fell by 20%. The linear dose-response slope was calculated as the last dose divided by the total dose given.
RESULTS—443 Dust samples were collected. The median cumulative exposure to dust was 110 years.mg/m³ with lower and upper quartiles at 70 and 160 years.mg/m³ Overall, no declines in FEV₁ and forced vital capacity (FVC) were found with increasing exposures. A dose-response relation was found between intensity of exposure on the one hand, and sore throat, increased prevalence of positive methacholine bronchial challenge tests, and steeper dose-response slope, on the other.
CONCLUSION—Exposure to oak and beech dust may lead to the development of sore throat and bronchial hyperresponsiveness.


Keywords: bronchial hyperresponsiveness; wood dust; beech; oak     

A population study on differences in the determinants of a specific shoulder disorder versus nonspecific shoulder pain without clinical findings

Musculoskeletal pain frequently occurs without particular clinical findings. Pain per se may be determined by factors other than those indicating a clinical disorder. The authors examined the prevalence and determinants of clinically diagnosed chronic rotator cuff tendinitis and self-reported nonspecific shoulder pain. The Health 2000 survey, carried out in 2000-2001 in Finland, included a nationally representative sample of 8,028 persons aged 30 years or more. In the present study, analyses were restricted to subjects aged 30-64 years who had held a job during the preceding 12 months. The prevalences of chronic rotator cuff tendinitis and nonspecific shoulder pain were 2.0% (78 of 3,909 subjects) and 12% (410 of 3,525 subjects), respectively. Nonspecific pain was related to burnout (adjusted odds ratio (OR) = 1.7, 95% confidence interval (CI): 1.4, 2.2), depression (among women, the adjusted OR was 1.8 (95% CI: 1.1, 2.9) for mild depression and 3.0 (95% CI: 1.6, 5.6) for severe depression), and inability to express one's feelings (alexithymia) (adjusted OR = 1.6, 95% CI: 1.1, 2.5). However, these factors were not associated with chronic rotator cuff tendinitis, determinants of which were work-related cumulative loading on the shoulder, age, and insulin-dependent diabetes mellitus (adjusted OR = 8.8, 95% CI: 1.9, 40.3). The determinants of specific musculoskeletal disorders differ from those of subjective complaints without clinical findings. Such complaints may be indicators of adverse psychological and psychosocial factors rather than the presence of an underlying pathologic condition.     

Investigation of a cluster of children with Down's syndrome born to mothers who had attended a school in Dundalk, Ireland

OBJECTIVES—To investigate a reported cluster of Down's syndrome in offspring of former pupils of a girls' school in Ireland, to establish the prevalence of Down's syndrome among live births in the area around the school, and to review the literature on the possible causes of reported clusters of Down's syndrome.
METHODS—Questionnaire survey of obstetric and personal histories of women who had attended the girls' school at Dundalk, County Louth, Republic of Ireland, at some time during 1956-7, and also of women who had attended another, nearby, girls' school during the same period. Comparison of observed numbers of cases of Down's syndrome identified by these surveys with maternal age adjusted expected numbers for the reported live births. Laboratory tests were conducted to verify and characterise the cases of Down's syndrome constituting the cluster. Retrospective collection and collation of data on Down's syndrome occurring among live births, and the compilation of maternal age specific incidences, in County Louth and in Newry and Mourne District in neighbouring Northern Ireland, during 1961-80. These rates were compared with reference rates and rates for other areas of Ireland.
RESULTS—Six children with Down's syndrome were confirmed among 387 reported live births to women who had been pupils at the girls' school in Dundalk during 1956-7, compared with 0.69 expected (nominal p<10^-4). Five of the affected births were to mothers under 30 years of age, against 0.15 expected (nominal p<10^-6), although only four of these mothers were attending the school at any one time. The origin of the non-disjunction was found to be maternal first meiotic in four children, mitotic after fertilisation in another (with the youngest mother), and in the remaining one could not be determined. The marked excess of Down's syndrome in births to young mothers did not extend to offspring of former pupils of the other Dundalk girls' school surveyed, or to live births in County Louth generally or in adjacent Newry and Mourne District.
CONCLUSION—A striking, highly localised, excess of Down's syndrome in births to young mothers who had attended a girls' school in Dundalk during 1956-57 has been confirmed. However, not all of the mothers of the affected children attended the school concurrently and the origin of non-disjunction in one child was an error occurring after conception. Some exposure essentially confined to girls attending the school at this time is a possible, although unlikely, explanation, but a review of potential risk factors does not suggest what this could be. Previous suggestions that an influenza epidemic or contamination from the Windscale nuclear reactor fire might be implicated, both of which occurred in October 1957, can be effectively dismissed because three of the women with affected offspring had left the school by then and had moved away from Dundalk, and Down's syndrome in the child of another mother originated in an error after fertilisation. Owing to the retrospective nature of the investigation and the characteristics of the cases, chance is the most likely explanation for the cluster.


Keywords: Down's syndrome; cluster; maternal exposure     

Relation between trihalomethane compounds and birth defects

OBJECTIVES—To evaluate the risk of birth defects relative to exposure to specific trihalomethanes in public water supplies.
METHODS—A retrospective cohort study was conducted based on data from a population based perinatal database in Nova Scotia, Canada and from the results of routine water monitoring tests. The cohort consisted of women who had a singleton birth in Nova Scotia between 1988 and 1995 and who lived in an area with a municipal water supply. The birth defects analyzed included neural tube defects, cardiovascular defects, cleft defects, and chromosomal abnormalities. Two of the four trihalomethane compounds occur in large enough concentrations to be analyzed (chloroform and bromodichloromethane (BDCM)).
RESULTS—Exposure to BDCM at concentrations of 20 µg/l or over was associated with an increased risk of neural tube defects (adjusted relative risk (RR) 2.5, 95% confidence interval (95% CI) 1.2 to 5.1) whereas exposure to chloroform was not. Exposure to BDCM of 20 µg/l and over was associated with decreased risks of cardiovascular anomalies (RR 0.3, 95% CI 0.2 to 0.7). There was a suggestion of an increased risk of chromosomal abnormalities associated with exposure to chloroform, and no evidence of any association between either trihalomethane compound and cleft defects.
CONCLUSIONS—In this cohort, differences were found in the RR associated with exposure to chloroform and BDCM for each of the congenital anomalies under study. These findings point to the importance of examining specific byproduct compounds relative to risk for these birth outcomes and in particular implicate BDCM and other correlated disinfection byproducts in the aetiology of neural tube defects.


Keywords: trihalomethanes; birth defects     

Lung and bladder cancer among workers in a Norwegian aluminium reduction plant

OBJECTIVE—To investigate the relation between exposure to polycyclic aromatic hydrocarbons (PAHs) and the incidence of lung and bladder cancer among aluminium production workers.
METHODS—The cohort comprised 1790 men employed for more than 5 years at a Norwegian aluminium plant contributing 36 587 person-years to the study. Historical exposure to PAHs was estimated by the use of industrial hygiene measurements and by a panel of three people familiar with the industry. Cancer incidence was investigated from 1953 to 1995. The observed cases of cancer among men were compared with expected numbers calculated from national rates for men, and dose-response relations were investigated by internal comparison by Poisson regression with age, period, smoking, and cumulative exposure included in the models. The effect of lagging exposure by 10, 20, and 30 years was also investigated.
RESULT—The present study showed no increased risk of urinary bladder cancer or lung cancer with increasing cumulative exposure to PAHs. No significant changes in risk were found for different lag times.
CONCLUSIONS—Due to the small size of this study, a minor increase in risk could not be excluded.


Keywords: cancer incidence; polycyclic aromatic hydrocarbons; Søderberg