Ulf Flodin

An epidemiologic study of bronchial asthma and smoking.

The role of smoking and air pollution in bronchial asthma in otherwise healthy adults is still unclear. We compared 79 cases of asthma, diagnosed between ages 20 and 65 years, with 304 randomly drawn population controls of similar age from the same catchment area as the cases. The comparison involved questionnaire information on smoking habits, occupational exposures, dwelling conditions, various suspect allergenic exposures, and atopy. Those who had smoked for 3 years or more, present or past, were at increased risk for bronchial asthma (odds ratio = 1.9; 95% confidence interval = 1.1–3.3). Adjustment by multiple logistic regression for age and gender as well as atopy and air pollution at work did not change the relative risk estimate. Exposure to environmental tobacco smoke, or passive smoking, at work involved a slightly greater risk. (Epidemiology 1995;6:503–505)

Background Radiation, Electrical Work, and Some Other Exposures Associated with Acute Myeloid Leukemia in a Case-Referent Study

The effect of potential risk factors for acute myeloid leukemia was evaluated in a case-referent study encompassing 59 cases and 354 referents, all of whom were alive. Information on exposure was obtained through a questionnaire mailed to the subjects. The possible effect of background radiation was evaluated by means of a gamma radiation index, which accounted for the differences between cases and referents in this respect, i.e., in time spent in concrete buildings both at home and at work places. In the 20-54 yr old age group, there was an association between leukemia morbidity and index of background radiation. X-ray treatment and electrical work were also associated with increased rate ratios. With regard to solvents, only styrene appeared as a risk factor, but the number of exposed subjects was small. Other exposures were less clearly associated with increased risks.

Organic solvents and multiple sclerosis : A synthesis of the current evidence

To evaluate the possible relation between exposure to organic solvents and the development of multiple sclerosis, we carried out a best-evidence synthesis of the available information. We found 13 studies with varying methodology that included information on solvent exposure. In 10 of the studies, there were indications of an increased risk of multiple sclerosis in relation to solvent exposure. We made three selections of studies for both pooled analyses and meta-analyses. The relative risk point estimates that we obtained varied from 1.7 to 2.6. Our evaluation is consistent with the hypothesis that organic solvents may be a cause of multiple sclerosis.

Chronic lymphatic leukaemia and engine exhausts, fresh wood, and DDT: a case-referent study.

The effect of potential risk factors for chronic lymphatic leukaemia was evaluated in a case-referent study encompassing 111 cases and 431 randomised referents, all alive. Information on exposure was obtained by questionnaires posted to the subjects. Crude rate ratios were increased for occupational exposure to solvents. DDT, engine exhausts, fresh wood (lumberjacks, paper pulp workers, and sawmill workers, for example) and also in farming. Further analysis of the material by means of the Miettinen confounder score technique reduced the number of rate ratios significantly exceeding unity to encompass only occupational exposure to engine exhaust, fresh wood, DDT, and contact with horses.

Neuropsychiatric effects of low exposure to styrene.

Workers exposed to styrene concentrations of about 50 mg/m3 at a plant manufacturing reinforced polyester boats were examined for neuropsychiatric symptoms both in close connection with exposure and also seven months after exposure had ceased. Physical workload is important for the uptake of styrene and was about 50 W at this plant. On the first occasion, after one week with no exposure, the workers reported a high frequency of neuropsychiatric symptoms such as fatigue, irritation, and forgetfulness whereas seven months later the frequency of these symptoms was low. These observations indicate that exposure to styrene at about 50 mg/m3 may induce reversible neuraesthenic symptoms. Even the relatively low Swedish standard (110 mg/m3 = 25 ppm) may, therefore, need revising.

MR Imaging in Solvent-Induced Chronic Toxic Encephalopathy:

PURPOSE To use MR to examine patients with CNS symptoms indicating +chronic intoxication. MATERIAL AND METHODS Thirty-two subjects exposed to industrial solvents for 5 to 28 years and 40 age-matched, healthy controls were examined. RESULTS All patients showed decreased signal in the basal ganglia on T2-weighted images. In 11 of the patients the white matter showed diffuse hyperintensity with loss of the grey-white matter discrimination and with distinct periventricular hyperintensities in 5 of the patients. The controls had no pathological changes in the brain. CONCLUSION Although the relatively small number of patients may obscure the significance, findings observed on T2-weighted images were patchy periventricular hyperintensities and hypointensities in the basal ganglia. Fast spin-echo is a good technique with fast acquisition of images with true spin-echo contrast features.

Cancer mortality among leather tanners

Workers were studied at a tannery that operated from 1873 to 1960, once one of the biggest in Scandinavia. The results show a slight numerical increase of deaths from cancer of the stomach and a significant, threefold excess mortality from cancer of the pancreas. Even in view of critical questions about validity it seems likely that this excess might be related to exposure to chemicals in tannery work.

Audiological Disturbances Caused by Long-term Exposure to Industrial Solvents. Relation to the Diagnosis of Toxic Encephalopathy

Sixty workers, consecutively admitted due to suspicion of solvent-induced chronic toxic encephalopathy (CTE), were investigated with pure-tone audiometry, determination of speech recognition of monosyllabic words and distorted speech and cortical response audiometry (CRA). Eighteen workers not exposed to occupational solvents and noise were also investigated. The scores in the distorted speech test were significantly lower and the CRA latencies were significantly longer in the solvent group than in the control group. There was no difference between the groups in the pure-tone and monosyllabic speech recognition tests. In the solvent group, 19 subjects had one or several pathological audiological test results (values exceeding the mean result of the control group by 2 SD). Independently of the audiological examination all the workers in the solvent group underwent the traditional clinical assessment of CTE, which is based on symptoms, history of exposure, clinical neurological examination and a neuropsychological investigation. They were classified in three groups--CTE, incipient CTE and non-CTE. There was no correlation between these groups and the audiological test results. A previous report on vestibular pathology in the same group of subjects and the present investigation on hearing deficits suggest that long-term exposure to solvents causes disturbances of the central pathways in the otovestibular system. Hitherto, no attention has been paid to these disturbances in the definition of the CTE syndrome.

The risk for multiple sclerosis in female nurse anaesthetists: a register based study

Background: Previous studies have suggested that exposure to organic solvents, including volatile anaesthetic agents, may be a risk factor for multiple sclerosis (MS), possibly in combination with genetic and other environmental factors. Aims: To further investigate the role of volatile anaesthetic agents having similar acute toxic effects to other organic solvents. Methods: Female nurse anaesthetists, other female nurses, and female teachers from middle and upper compulsory school levels were identified and retrieved from the 1985 census, Statistics Sweden. By means of the unique personal identity number in Sweden, these individuals were linked with the disability pension registers at The National Social Insurance Board and also with data on hospital care 1985–2000 at The National Board of Health and Welfare. Results: The cumulative incidence rate ratio of MS was found to be increased in female nurse anaesthetists in relation to other nurses (statistically not significant) and teachers (statistically significant), respectively. Conclusions: These findings give some support to previous findings of an increased risk for MS in nurse anaesthetists. This is interesting in the context of previous observations of organic solvents in general as a potential risk factor in MS.

Multiple sclerosis in nurse anaesthetists

Background: Volatile anaesthetics are chemically related to organic solvents used in industry. Exposure to industrial solvents may increase the incidence of multiple sclerosis (MS). Aim: To examine the risk among nurse anaesthetists of contracting MS. Methods: Nurses with MS were identified by an appeal in the monthly magazine of the Swedish Nurse Union and a magazine of the Neurological Patients Association in Sweden. Ninety nurses with MS responded and contacted our clinic. They were given a questionnaire, which was filled in by 85 subjects; 13 of these were nurse anaesthetists. The questionnaire requested information about work tasks, exposure, diagnosis, symptoms, and year. The number of active nurse anaesthetists was estimated based on information from the National Board of Health and Welfare and The Nurse Union. Incidence data for women in the region of Gothenburg and Denmark were used as the reference to estimate the risk by calculation of the standardised incidence ratio (SIR). Results: Eleven of the 13 nurse anaesthetists were exposed to anaesthetic gases before onset of MS. Mean duration of exposure before diagnosis was 14.4 years (range 4–27 years). Ten cases were diagnosed in the study period 1980–99, resulting in significantly increased SIRs of 2.9 and 2.8 with the Gothenburg and the Danish reference data, respectively. Conclusion: Although based on crude data and a somewhat approximate analysis, this study provides preliminary evidence for an excess risk of MS in nurse anaesthetists. The risk may be even greater than observed, as the case ascertainment might have been incomplete because of the crude method applied. Further studies in this respect are clearly required to more definitely assess the risk.