Residential Exposure to PM2.5 Components and Risk of Childhood Non-Hodgkin Lymphoma in Denmark: A Nationwide Register-Based Case-Control Study.

Ulla Arthur Hvidtfeldt,Camilla Geels,Lise M Frohn,Jesper Heile Christensen,Matthias Ketzel,Mette Sørensen,Ole Raaschou-Nielsen,Friederike Erdmann,Jørgen Brandt,Stine Kjaer Urhoj

doi:10.3390/ijerph17238949

Abstract

In a recent study, we observed an increased risk of childhood non-Hodgkin lymphoma (NHL) associated with exposure to fine atmospheric particulate matter (PM2.5) and black carbon (BC). In this nationwide register-based case-control study, we focus on specific components of PM2.5 in relation to childhood NHL in Denmark (1981–2013) by identifying all incidents of childhood NHL cases in the Danish Cancer Registry (n = 170) and four (cancer-free) randomly selected controls matched by date of birth and sex. We applied PM2.5 concentrations and the following sub-components: secondary organic aerosols (SOA), secondary inorganic aerosols (SIA; i.e., NO3−, NH4+ and SO42−), BC, organic carbon (OC) and sea salt. We calculated a time-weighted exposure average from birth to index-date at all addresses. Odds ratios (ORs) were adjusted for register-based socio-demographic variables. We observed adjusted ORs and 95% confidence intervals (95% CI) of 2.05 (1.10, 3.83) per interquartile range (IQR, 4.83 µg/m3) PM2.5 and 1.73 (0.68, 4.41) per IQR (3.71 µg/m3) SIA, 0.95 (0.71, 1.29) per IQR (0.05 µg/m3) SOA, 1.22 (1.02, 1.46) per IQR (0.39 µg/m3) BC, 1.02 (0.83, 1.26) per IQR (0.56 µg/m3) OC and 1.01 (0.79, 1.30) per IQR (0.87 µg/m3) sea salt, respectively. The estimates were attenuated after adjustment for PM2.5, whereas the OR for PM2.5 remained increased regardless of adjustment for specific components. The findings indicate that the previously observed relation between PM2.5 and childhood NHL may be related to BC (as reported in our previous study) but also partly to SIA, but the role of specific chemical components of PM2.5 remains ambiguous.

Highlights

Non-Hodgkin lymphomas (NHL) are a diverse group of malignancies of the immune system.Worldwide, non-Hodgkin lymphoma (NHL) is the third most common type of childhood cancer (0–19 years) after leukemia and tumors of the central nervous system [1]
Cases and controls did not differ considerably according to any of the considered covariates, except for minor differences in parental educational level, with a tendency towards less educated mothers and fathers among cases compared to controls
For the subsample of cases and controls with information on neighborhood socioeconomic status (SES), cases resided in a neighborhood with a high proportion of inhabitants with low income to a higher degree than controls, but cases were more likely to live in a neighborhood with a low proportion of manual workers (Table 1)

Summary

Introduction

Non-Hodgkin lymphomas (NHL) are a diverse group of malignancies of the immune system.Worldwide, NHL is the third most common type of childhood cancer (0–19 years) after leukemia and tumors of the central nervous system [1]. The observed rise in the incidence of childhood NHL over time combined with the geographical variation suggest an environmental component in the etiology of NHL. Maternal domestic pesticide exposure during pregnancy, exposure to ionizing radiation and parental smoking have been suggested as potential environmental risk factors [3,4]. Ambient air pollution is classified as a Group 1 carcinogen [5]; past studies have not reported clear evidence of an association with childhood NHL [6]. A recent Danish case-control study reported an association with maternal residential benzene exposure during pregnancy [7]. In a recently published study, we observed an association between residential exposure to ambient fine particulate matter (PM2.5 )

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Results

Conclusion