OBJECTIVES: This study attempts to demonstrate a calculation of the occupational lung cancer burden using economically active men in Sweden as an example. METHODS: Estimates were calculated using Swedish register data on occupation in 1970, lung cancer incidence in 1971-1989, smoking frequencies in 1963, and the formula I = RI0F + I0(1-F), where I is the overall incidence, R is the relative risk associated with a factor (here smoking), F is the fraction of persons at risk (smokers), and I0 is the incidence among those not at risk (nonsmokers). RESULTS: Farmers, gardeners, forestry workers, and fishermen had the lowest lung cancer risk (42.1 per 100,000 person-years) and a smoking frequency of 44.7%. Their I0 was 12.6 or 8.4 per 100,000 person-years, taking R for smoking as 6 or 10, respectively. From these I0 estimates, the expected rates for white- and blue-collar workers (smoking frequencies 52.7 and 57.7%, respectively) were 45.8 and 49.1 per 100,000 person-years, as compared with the 22% and 57% higher observed rates, respectively. Weighing these excesses proportionally according to the sizes of the three occupational categories gave, respectively for R equal to 6 and 10, occupation-related excesses of 39% and 32% and population-attributable risks of 28% and 24%. CONCLUSIONS: About one-fourth of the lung cancers that occur among economically active Swedish men seem to have been related to occupation. This figure agrees with estimates made by other methods in Nordic countries. Due to interaction, the population-attributable risk from smoking is still high, 73% and 83% at relative risk values of 6 and 10, respectively.
STUDY OBJECTIVE: Is there any epidemiologically visible influence on the cancer incidence after the Chernobyl fallout in Sweden? DESIGN: A cohort study was focused on the fallout of caesium-137 in relation to cancer incidence 1988-1996. SETTING: In northern Sweden, affected by the Chernobyl accident in 1986, 450 parishes were categorised by caesium-137 deposition:
Concerns in Sweden about indoor radon around 1980 prompted measurements of gamma-radiation from the facades of houses to identify those constructed of uranium-containing alum shale concrete, with potentially high radon concentrations. To evaluate any possible risk of acute lymphocytic leukemia from exposure to elevated gamma-radiation in these homes, we identified the acute lymphocytic leukemia cases less than 20 years of age in Sweden during 1980-1989 as well as eight controls per case from the population registry, matching on age, gender, and county. Using the existing measurements, exposure was assessable for 312 cases and 1,418 controls from 151 properly measured municipalities. A conditional logistic odds ratio of 1.4 (95% confidence interval = 1.0-1.9) was obtained for those ever having lived in alum shale concrete houses, with the average exposure exceeding 0.10 microsieverts per hour. Comparing those who ever lived in alum shale concrete houses (divided by higher and lower annual average exposure) with those who never lived in such houses, we found a weak dose-response relation. The results suggest some risk of acute lymphocytic leukemia from indoor ionizing radiation among children and young adults.
The aim of this study was to identify and discuss validity aspects on so called negative and non-positive studies. Arguments and examples are drawn from experiences in occupational health epidemiology regarding the interpretation of more or less equivocal study results. A negative study may be defined as showing a result that goes against the investigated hypothesis of an increased (or prevented) risk. Traditionally, studies with a risk estimate (relative risk or odds ratio) above, but close to unity are also referred to as negative, given a narrow confidence interval (CI) that includes unity. A risk estimate above unity with the CI including unity is non-positive, however, but an estimate below unity with upper CI bond exceeding unity might be seen as possibly negative or non-negative. A weaker "significance" than usually required should perhaps be accepted when evaluating serious hazards. In contrast to positive studies, the negative and non-positive studies tend to escape criticism in spite of questionable validity that may have obscured existing risks (or preventive effects). Even stronger arguments can be made in criticising negative and non-positive studies than positive studies, for example, regarding selection phenomena, and observational problems regarding exposure and outcome. Negative confounding should be considered although usually weak. In case-control studies, so called over-matching may obscure an existing risk as could the "healthy worker effect" in cohort studies. Small scale non-positive studies should be made available for meta-analyses and when considering studies that do not convincingly show a risk; those who are exposed should be given the "benefit of the doubt".
OBJECTIVES: Using environmental concentrations and Geographic Information Systems (GIS) to model human exposure is an emerging tool in environmental epidemiology. To evaluate the usefulness of this, we investigated to what extent cadmium and lead concentrations in soil and moss could be used as potential determinants for cadmium and lead exposure for a population living near a battery plant. METHODS: Cadmium in urine and blood and lead in blood, as well as food, smoking habits, places of residence, occupations and health, were determined for 512 individuals living near a closed down battery factory in Sweden. Cadmium and lead contents in moss were available through previous assessments by the Geological Survey of Sweden. Soil samples had been collected at various distances from the factory, and analyzed for cadmium and lead contents in 1990. Kriging technique in GIS was used to create areas with different metal concentrations based on these measurements. By linking individual address coordinates to mapped concentration levels, each study subject home address received a value of cadmium and lead in moss and soil. RESULTS: We found a statistically significant association between lead in soil and lead in blood, for female subjects eating homegrown vegetables regularly. No significant association was found between cadmium in soil and cadmium in urine for either gender in the study population. No clear associations were found for either gender regarding lead and cadmium in moss and lead in blood or cadmium in urine or in blood. CONCLUSION: In general, environmental concentrations may not be useful surrogates for assessing human exposure to lead and cadmium, but concentrations of metals in soil around emitting point sources can be a complement for estimating the exposure in certain subgroups.