Evidence of space-time clustering of childhood acute lymphoblastic leukaemia in Sweden.
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We have examined 645 recorded cases of childhood acute lymphatic leukaemia (ALL) in Sweden during 1973-89 to identify space-time clustering by using the close-pair method of Knox. The records included date of birth and of diagnosis as well as addresses at birth and at diagnosis. There was a significant excess of case pairs close in date of birth and place of birth in the 5- to 15-year age group. (+info)
Juvenile hypothyroidism among two populations exposed to radioiodine.
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We found an epidemic of juvenile hypothyroidism among a population of self-defined "downwinders" living near the Hanford nuclear facility located in southeast Washington State. The episode followed massive releases of 131I. Self-reported data on 60 cases of juvenile hypothyroidism (<20 years of age) among a group of 801 Hanford downwinders are presented, as well as data concerning the thyroid status of approximately 160,000 children exposed to radioiodine before 10 years of age as a result of the 26 April 1986 Chernobyl explosion in the former Soviet Union. These children were residents of five regions near Chernobyl. They were examined by standardized screening protocols over a period of 5 years from 1991 to 1996. They are a well-defined group of 10 samples. Fifty-six cases of hypothyroidism were found among boys and 92 among girls. Body burdens of 137Cs have been correlated with hypothyroidism prevalence rates. On the other hand, the group of juvenile (<20 years of age) Hanford downwinders is not a representative sample. Most of the 77 cases of juvenile hypothyroidism in the Hanford group were diagnosed from 1945 to 1970. However, the ratio of reported cases to the county population under 20 years of age is roughly correlated with officially estimated mean levels of cumulative thyroid 131I uptake in these counties, providing evidence that juvenile hypothyroidism was associated with radioiodine exposures. Because even subtle hypothyroidism may be of clinical significance in childhood and can be treated, it may be useful to screen for the condition in populations exposed to radioiodine fallout. Although radiation exposure is associated with hypothyroidism, its excess among fallout-exposed children has not been previously quantified. (+info)
An assessment of spatial clustering of leukaemias and lymphomas among young people in New Zealand.
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STUDY OBJECTIVE: To assess spatial clustering of childhood leukaemias and lymphomas in New Zealand, using a national dataset from a country with no nuclear installations. DESIGN: New Zealand Map Grid coordinates, derived from the birth addresses of cases and controls were used in clustering analyses that applied Cuzick and Edwards' method. SETTING: The whole of New Zealand. PARTICIPANTS: The cases were ascertained from the New Zealand Cancer Registry. They were diagnosed with leukaemia or lymphoma at ages 0-14 years during the period 1976 to 1987. For Hodgkin's disease, the age range was extended to include those aged from 0-24 years. The cancer registrations were linked with national birth records, to obtain the birth addresses of the cases. The controls were selected at random from birth records, with matching to cases (1:1) on age and sex. The analyses included 600 cases and 600 controls. MAIN RESULTS: There was no statistically significant spatial clustering for any tumour group overall, including acute lymphoblastic leukaemia, acute nonlymphoblastic leukaemia, other leukaemias, non-Hodgkin's lymphomas, Hodgkin's disease, and all these combined. Significant clustering was found in a sub-analysis for one of three age specific subgroups of acute lymphoblastic leukaemia (ages 10-14 years, p = 0.003). CONCLUSION: The subgroup finding may have been real or a chance association, as several comparisons were made. This study found little evidence for spatial clustering of leukaemias or lymphomas in a population with no nuclear installations. (+info)
Suspected nasopharyngeal carcinoma in three workers with long-term exposure to sulphuric acid vapour.
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Sulphuric acid vapour has been suspected of being an industrial carcinogen. In this study, a cluster is presented of three patients with nasopharyngeal carcinoma (NPC) who worked in the same building of a telecommunications conveyance station in southern Taiwan with long term exposure to sulphuric acid vapour concentrations as high as 0.18 mg/m3. All three workers were diagnosed with NPC within a 5 month period between September 1992, and March 1993. Compared with 19 other healthy workers from the same building, these three workers with NPC had worked significantly longer in this building than had the others (mean (SD) (years): 12.7 (0.6) v 7.4 (4.4); p = 0.01). With an in situ nucleic acid hybridisation and immunostaining method for colocalised Epstein-Barr virus (EBV) and secretory component (SC) protein among biopsy specimens of these three patients with NPCs, it was found that some tumour cells did not contain EBV and SC protein staining signals. These results indicate that EBV infection is not the only risk factor for NPC and long term exposure to relatively low concentrations of sulphuric acid vapour may be associated with the development of NPC. (+info)
American cutaneous leishmaniasis in Southeast Brazil: space-time clustering.
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BACKGROUND: American cutaneous leishmaniasis (ACL) is endemic in many rural areas of Brazil where different transmission patterns of the disease have been described. This ecological study was carried out in a municipality located in Southeast Brazil and aimed to investigate the space-temporal patterns of the disease and environmental risk factors from 1966 to 1996. METHODS: Incident ACL cases were defined by clinical diagnosis, confirmed by a positive skin test and/or parasitological examination. Age-adjusted morbidity rate of ACL was calculated by year for this municipality and their different census enumeration districts. The homogeneity chi2 test, Moran and empirical Bayes index and Knox procedure were employed for testing the significance of clusters in time, space and in time-space, respectively. A Poisson regression model was used to identify environmental factors related to rate variability. RESULTS: A total of 1712 new ACL cases were reported with a yearly incidence rate of 48/100000 inhabitants. Higher incidence rates were detected in 1968, 1974, and 1988 (100, 160, and 190 cases/100000, respectively) with evidence of spatial clustering from 1986 to 1993. Significant space-time clustering with epidemic peaks followed by low incidence in subsequent periods was observed. The incidence rates of ACL were independently associated with rural areas; areas lacking sanitary installations and with higher proportion of exposed garbage (P < 0.01). CONCLUSIONS: This study suggests that ACL rates vary across space and time. Rural areas and some environmental factors could explain part of this variation. Environmental modifications in the vicinity of households over time and accumulation of susceptible individuals are discussed as possible factors responsible for variability. (+info)
The existence of geographical clusters of cases of inflammatory polyarthritis in a primary care based register.
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OBJECTIVES: To determine whether there is any evidence that there are spatial clusters of rheumatoid arthritis in particular, and inflammatory arthritis in general. METHODS: Setting was a population based incidence register of inflammatory arthritis: the Norfolk Arthritis Register (NOAR). All cases identified between 1990-1995 were mapped to place of residence. Statistical evidence of clustering was determined by calculating Poisson probabilities in putative areas. RESULTS: Three clusters were identified including one small area (population 85) where five unrelated cases developed during this time period. There was no obvious greater disease homogeneity within clusters and no common environmental factors were identified. CONCLUSION: Rare clusters of inflammatory polyarthritis do occur. Their significance and cause remain to be elucidated. (+info)
Soft-tissue sarcoma and non-Hodgkin's lymphoma clusters around a municipal solid waste incinerator with high dioxin emission levels.
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Overall evidence from epidemiologic studies in the workplace suggests that dioxin is a human carcinogen, but whether low doses affect the general population remains to be determined. The authors examined the spatial distribution of soft-tissue sarcomas and non-Hodgkin's lymphomas around a French municipal solid waste incinerator with high emission levels of dioxin (16.3 ng international toxic equivalency factor/m3). Not consistently associated with dioxin exposure,-Hodgkin's disease served as the control cancer category. Clusters were identified from 1980 to 1995 in the area ("departement') of Doubs by applying a spatial scan statistic to 26 electoral wards. The most likely and highly significant clusters found were identical for soft-tissue sarcomas and non-Hodgkin's lymphomas and included the area around the municipal solid waste incinerator; standardized incidence ratios were 1.44 (observed number of cases = 45, focused test p value = 0.004) and 1.27 (observed number of cases = 286, focused test p value = 0.00003), respectively. Conversely, Hodgkin's disease exhibited no specific spatial distribution. Confounding by socioeconomic status, urbanization, or patterns of medical referral seemed unlikely to explain the clusters. Although consistent, these findings should be confirmed by further investigation (e.g., a case-control study in which dioxins are measured in biologic tissues) before clusters of soft-tissue sarcoma and non-Hodgkin's lymphoma are ascribed to dioxin released by the municipal solid waste incinerator. (+info)
Investigation of a cluster of children with Down's syndrome born to mothers who had attended a school in Dundalk, Ireland.
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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. (+info)