Risk of cancer in the vicinity of municipal solid waste incinerators: importance of using a flexible modelling strategy.

BACKGROUND: We conducted an ecological study in four French administrative departments and highlighted an excess risk in cancer morbidity for residents around municipal solid waste incinerators. The aim of this paper is to show how important are advanced tools and statistical techniques to better assess weak associations between the risk of cancer and past environmental exposures. METHODS: The steps to evaluate the association between the risk of cancer and the exposure to incinerators, from the assessment of exposure to the definition of the confounding variables and the statistical analysis carried out are detailed and discussed. Dispersion modelling was used to assess exposure to sixteen incinerators. A geographical information system was developed to define an index of exposure at the IRIS level that is the geographical unit we considered. Population density, rural/urban status, socio-economic deprivation, exposure to air pollution from traffic and from other industries were considered as potential confounding factors and defined at the IRIS level. Generalized additive models and Bayesian hierarchical models were used to estimate the association between the risk of cancer and the index of exposure to incinerators accounting for the confounding factors. RESULTS: Modelling to assess the exposure to municipal solid waste incinerators allowed accounting for factors known to influence the exposure (meteorological data, point source characteristics, topography). The statistical models defined allowed modelling extra-Poisson variability and also non-linear relationships between the risk of cancer and the exposure to incinerators and the confounders. CONCLUSION: In most epidemiological studies distance is still used as a proxy for exposure. This can lead to significant exposure misclassification. Additionally, in geographical correlation studies the non-linear relationships are usually not accounted for in the statistical analysis. In studies of weak associations it is important to use advanced methods to better assess dose-response relationships with disease risk.

Risk for non Hodgkin's lymphoma in the vicinity of French municipal solid waste incinerators.

BACKGROUND: Dioxin emissions from municipal solid waste incinerators are one of the major sources of dioxins and therefore are an exposure source of public concern. There is growing epidemiologic evidence of an increased risk for non-Hodgkin's lymphoma (NHL) in the vicinity of some municipal solid waste incinerators with high dioxin emission levels. The purpose of this study was to examine this association on a larger population scale. METHODS: The study area consisted of four French administrative departments, comprising a total of 2270 block groups. NHL cases that had been diagnosed during the period 1990-1999, and were aged 15 years and over, were considered. Each case was assigned a block group by residential address geocoding. Atmospheric Dispersion Model System software was used to estimate immissions in the surroundings of 13 incinerators which operated in the study area. Then, cumulative ground-level dioxin concentrations were calculated for each block group. Poisson multiple regression models, incorporating penalized regression splines to control for covariates and dealing with Poisson overdispersion, were used. Five confounding factors were considered: population density, urbanisation, socio-economic level, airborne traffic pollution, and industrial pollution. RESULTS: A total of 3974 NHL incident cases was observed (2147 among males, and 1827 among females) during the 1990-1999 time period. A statistically significant relationship was found at the block group level between risk for NHL and dioxin exposure, with a relative risk (RR) of 1.120 (95% confidence interval [CI] 1.002 - 1.251) for persons living in highly exposed census blocks compared to those living in slightly exposed block groups. Population density appeared positively linked both to risk for NHL and dioxin exposure. Subgroup multivariate analyses per gender yielded a significant RR for females only (RR = 1.178, 95% CI 1.013 - 1.369). CONCLUSION: This study, in line with previous results obtained in the vicinity of the incinerator located in Besançon (France), adds further evidence to the link between NHL incidence and exposure to dioxins emitted by municipal solid waste incinerators. However, the findings of this study cannot be extrapolated to current incinerators, which emit lower amounts of pollutants.

Short term effects of air pollution on hospitalizations for cardiovascular diseases in eight French cities: the PSAS program.

INTRODUCTION: Short term associations between air pollution indicators and hospitalizations for cardiovascular diseases have been suggested by epidemiological and clinical studies. The present study aims at estimating the association between particles with diameter <10 microm (PM(10)), nitrogen dioxide (NO(2)) and ozone and hospitalizations for cardiovascular diseases in eight French cities during the 1998-2003 period. METHODS: The daily number of hospitalizations in each city was extracted from the French hospital information system (PMSI) for cardiovascular diseases, cardiac diseases, ischemic heart diseases and stroke. Excess relative risks (ERRs) of hospitalization associated with a 10 microg/m(3) increase in pollutant levels were estimated in each city by fitting a Poisson regression model, controlling for well-known confounding factors and temporal trends. City-specific results were then combined by inverse variance weighting. RESULTS: Daily number of hospitalizations for cardiovascular diseases was associated with PM(10) levels (for a 10 microg/m(3) increase, ERR=0.8%, 95% CI: [0.2, 1.5]), with NO(2) (1.1%, [0.6, 1.6]) but not with ozone (0.1% [-0.2%, 0.5%]). Associations were stronger in people aged 65 years and over, and when only hospitalizations for ischemic heart diseases were considered. No association was found between strokes and air pollution levels. DISCUSSION: Our study suggests that the ambient levels of air pollutants currently experienced in the eight French cities, which are close to European air quality guidelines, are yet linked to a short term increase of hospitalizations for cardiovascular diseases. These results are consistent with epidemiological and toxicological data on the cardiovascular effects of air pollution.

Impact of the 2003 heatwave on all-cause mortality in 9 French cities.

BACKGROUND: A heatwave occurred in France in August 2003, with an accompanying excess of all-cause mortality. This study quantifies this excess mortality and investigates a possible harvesting effect in the few weeks after the heatwave. METHODS: A time-series study using a Poisson regression model with regression splines to control for nonlinear confounders was used to analyze the correlation between heatwave variable and mortality in 9 French cities. RESULTS: After controlling for long-term and seasonal time trends and the usual effects of temperature and air pollution, we estimated that 3,096 extra deaths resulted from the heatwave. The maximum daily relative risk of mortality during the heatwave (compared with expected deaths at that time of year) ranged from 1.16 in Le Havre to 5.00 in Paris. There was little evidence of mortality displacement in the few weeks after the heatwave, with an estimated deficit of 253 deaths at the end of the period. CONCLUSIONS: The heatwave in France during August 2003 was associated with a large increase in the number of deaths. The impact estimated using a time-series design was consistent with crude previous estimates of the impact of the heatwave. This finding suggests that neither air pollution nor long-term and seasonal trends confounded previous estimates. There was no evidence to suggest that the extras deaths associated with the heatwave were simply brought forward in time.

Vaccines administered simultaneously: directions for new combination vaccines based on an historical review of the literature.

OBJECTIVES: The recognized benefits of administering vaccines simultaneously has encouraged vaccine producers to develop combination vaccines. If contemporary research and development can realize vaccines that achieve the current standards for safety, immunogenicity, and efficacy, other specific vaccine associations may also merit reconsideration as combination vaccines. METHODS: An historical review of the vaccine association literature reveals two important themes: first, the programs of mass vaccination, in particular, the eradication of smallpox, sessions where multiple vaccines (other than the smallpox vaccine) were given concurrently, and the Expanded Programme on Immunization (EPI); and, second, the domain of travel vaccines, including travellers to a disease-endemic country (such as migrants, tourists, military personnel, or expatriates) and WHO requirements for international travellers. RESULTS/CONCLUSIONS: Based on this historical review, combination vaccines worth reconsideration could fill epidemiologic niches in the EPI with, for instance, a measles--yellow fever, a measles--Japanese encephalitis or a pertussis-based paediatric combination rabies vaccine. Furthermore, other combinations could broaden protection against the pathogens responsible for meningitis, pneumonia, or enteric diseases. Nevertheless, complex issues such as necessity, feasibility, or affordability will ultimately determine if any one of these becomes a combination vaccine.