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

Abstract

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.

Figure 1

Example of ground-level concentration modelling in the vicinity of a municipal solid waste incinerator (La Tonche, Isère, France).

Figure 2

Dioxin exposure (modelled ground-level concentrations) distribution within modelled zones (520 block groups, France). P2.5 = 2.5^th percentile (1.25 × 10^-4 μg/m²/year); P50 = 50^th percentile (4.25 × 10^-3 μg/m²/year); P90 = 90^th percentile (1.78 × 10^-2 μg/m²/year).

Figure 3

Log-transformed SIR for non-Hodgkin's lymphoma vs. square root transformed cumulative ground-level dioxin concentration (μg/m²/year) (1990–1999, France).