Olav Axelson

Residential Radon Exposure and Lung Cancer in Sweden

BACKGROUND Residential radon is the principal source of exposure to ionizing radiation in most countries. To determine the implications for the risk of lung cancer, we performed a nationwide case-control study in Sweden. METHODS The study included 586 women and 774 men 35 to 74 years of age with lung cancer that was diagnosed between 1980 and 1984. For comparison, 1380 female and 1467 male controls were studied. Radon was measured in 8992 dwellings occupied by the study subjects at some time since 1947. Information on smoking habits and other risk factors for lung cancer was obtained from questionnaires. RESULTS Radon levels followed a log-normal distribution, with geometric and arithmetic means of 1.6 and 2.9 pCi per liter (60.5 and 106.5 Bq per cubic meter), respectively. The risk of lung cancer increased in relation to both estimated cumulative and time-weighted exposure to radon. In comparison with time-weighted average radon concentrations up to 1.4 pCi per liter (50 Bq per cubic meter), the relative risk was 1.3 (95 percent confidence interval, 1.1 to 1.6) for average radon concentrations of 3.8 to 10.8 pCi per liter (140 to 400 Bq per cubic meter), and it was 1.8 (95 percent confidence interval, 1.1 to 2.9) at concentrations exceeding 10.8 pCi per liter. The estimates of risk were in the same range as those projected from data in miners. The interaction between radon exposure and smoking with regard to lung cancer exceeded additivity and was closer to a multiplicative effect. CONCLUSIONS Residential exposure to radon is an important cause of lung cancer in the general population. The risks appear consistent with earlier estimates based on data in miners.

Soft-tissue sarcomas and exposure to chemical substances: a case-referent study.

In 1977 several patients were seen with soft-tissue sarcomas and previous exposure to phenoxy acids. This clinical observation resulted in a cases-referent (case-control) study being undertaken which showed that exposure to phenoxy acids or chlorophenols, which are chemically related, gave a roughly six-fold increase in the risk for this type of tumour. A further case-referent study of soft-tissue sarcomas has now been performed to confirm these earlier findings and also to obtain further information on the effects of different phenoxy acids. This new investigation gave an increase of the same magnitude in the risk for soft-tissue sarcomas after exposure to phenoxy acids or chlorophenols, but this risk related also to exposure to phenoxy acids free from impurities, such as polychlorinated dibenzodioxins and dibenzofurans.

Nutritional and occupational factors influencing the risk of Parkinson's disease : a case-control study in southeastern Sweden

To investigate the possible impact of nutritional and environmental risk factors for idiopathic Parkinsons disease (IP), a case‐control study was performed in the county of Östergötland in southeastern Sweden. The study involved 113 cases of IP and 263 control subjects. Dietary, drinking, and smoking habits, as well as previous occupation, were requested in a structured questionnaire.

A case-referent study on neuropsychiatric disorders among workers exposed to solvents.

Published reports give justification for the belief that long-term exposure to solvents might induce chronic but nonspecific neuropsychiatric conditions. This case-referent study of data from a regional Swedish pension fund register indicated a risk ration of 1.8 in regard to nonspecific neuropsychiatric disorders among workers such as painters, varnishers and carpetlayers who are exposed to solvents as compared to workers not so exposed. Moreover a dose-response relationship seems to exist between exposure in terms of occupational years and neuropsychiatric conditions, the result being that persons affected are considered eligible for disability pensions.

Malignant lymphomas and occupational exposures.

The effects of potential risk factors for Hodgkins disease (HD) and for non-Hodgkin lymphomas (NHL) were evaluated in a case-referent study encompassing 54 cases of HD, 106 cases of NHL, and 275 referents, all alive. Exposure information was obtained by questionnaires posted to the subjects. Crude rate ratios were increased for various occupational exposures including solvents, welding, wood preservatives, phenoxy acids, and fresh wood (sawmill workers, lumberjacks, paper pulp workers). After further analyses based on logistic regression occupational exposures to welding and creosote remained as significant risk factors for HD. For NHL, occupational exposures to solvents, phenoxy acids, and creosote but also work as carpenter or cabinet maker and contacts with pets (other than dogs, cats, and birds) were associated with significantly increased risks.

A case-control study of motor neurone disease: its relation to heritability, and occupational exposures, particularly to solvents.

Motor neurone disease (MND) was studied in relation to various determinants in a case-control study covering nine counties in southern Sweden. A questionnaire about occupational exposures, medical history, lifestyle factors etc was given to all cases in the age range 45-79 and to a random sample of 500 population controls in the same age range. The questionnaires were answered by 92 cases and 372 controls, a response rate of 85% and 75% respectively. Among men high Mantel-Haenszel odds ratios (MHORs) were obtained for electricity work (MHOR = 6.7, 95% confidence interval (95% CI) 1.0-32.1), welding (MHOR = 3.7, 95% CI 1.1-13.0), and impregnating agents (MHOR = 3.5, 95% CI 0.9-13.1). Heritability with regard to a neurodegenerative disease or thyroid disease seemed to predispose to a risk of developing MND (OR = 2.1, 95% CI 1.0-4.3). The highest OR was found for the combination of such heritability, exposure to solvents, and male sex (OR = 15.6, 95% CI 2.8-87.0), a combination that occurred for seven cases and three controls. Hereditary factors and external exposures had a different distribution among cases with the spinal type of MND than among cases with involvement of the pyramidal tract or bulbar paresis also.

Prostate cancer and exposure to pesticides in agricultural settings

Our study evaluates the association between prostate cancer and exposure to pesticides in agricultural settings in Italy. The data were derived from a hospital‐based multi‐site case‐control study carried out in 5 rural areas between 1990–92. In our study, 124 new cases of prostate cancer were ascertained and interviewed, along with 659 cancer controls. A team of agronomists assessed past exposure to pesticides by using a checklist of 100 chemical families and 217 compounds applied from 1950–85 in the areas considered. The association between prostate cancer and different occupational risk factors was measured by maximum likelihood estimation of the odds ratio, controlling for potential confounders. “Ever been employed in agriculture” was associated with a 40% increased risk (OR = 1.4, 95% CI = 0.9–2.0). Prostate cancer was also related positively to food and tobacco (OR= 2.1, 95% CI = 1.1–4.1), and chemical products (OR = 2.2, 95% CI = 0.7–7.2) industries. The analyses carried out to estimate the association between different types of pesticides and prostate cancer showed increased risks among farmers exposed to organochlorine insecticides and acaricides (OR = 2.5, 95% CI = 1.4–4.2), more specifically to the often contemporary used compounds DDT (OR = 2.1, 95% CI = 1.2–3.8), and dicofol (OR = 2.8, 95% CI = 1.5–5.0), whose effects could not be well separated.

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)

Colon cancer, physical activity, and occupational exposures. A case‐control study

A case‐control study on colon cancer was conducted encompassing 329 cases and 658 controls. Occupations and various exposures were assessed by questionnaires. A decreased risk was found in persons with physically active occupations. This effect was most pronounced in colon descendens and sigmoideum with an odds ratio (OR) of 0.49 whereas no reduced risk was found for right‐sided colon cancer. Regarding specific jobs, reduced ORs were found for agricultural, forestry, and saw mill workers and increased OR for railway employees. High‐grade exposure to asbestos or to organic solvents gave a two‐fold increased risk. Regarding exposure to trichloroethylene in general, a slightly increased risk was found whereas such exposure among dry cleaners gave a seven‐fold increase of the risk.

Age-standardized incidence and prevalence of Parkinson's disease in a Swedish community☆

Parkinsons disease (PD) shows a geographical variation. All prescriptions for anti-parkinsonian drugs were recorded for a half-year in a region with low L-dopa consumption. Hospital and outpatient records were studied and physicians were asked to supply details of PD patients in the region, with 147,777 inhabitants. The crude prevalence was 115 PD per 100,000 inhabitants, based on 170 cases. In contrast to other studies we report an age-standardized prevalence, which was 76 per 100,000, using the European Standard Population as reference. The corresponding approximate incidences were 11.0 (crude) and 7.9 (age-standardized) per 100,000 person-years. Male preponderance appeared in all age groups. Mean age at onset was 65.6 years, the highest figure reported. Variation between studies for age at onset, differences in prevalence, and male preponderance suggest environmental risk factors to be of importance for PD.