Childhood leukaemia risk and residential proximity to busy roads

"Characterization of residential proximity to sources of environmental carcinogens in clusters of Acute Lymphoblastic Leukemia in San Luis Potosi, Mexico"

BACKGROUND

Acute Lymphoblastic Leukemia (ALL) is the most prevalent neoplasia in children and teenagers in Mexico. Although epidemiological data supports that children's residence close to emissions from vehicular traffic or industrial processes increases the risk of ALL; and the IARC states that benzene, PAHs, and PM 2.5 are well-known environmental carcinogens, there is a gap in linking these carcinogenic hazards with the sources and their distribution from scenario perspective.

AIM

To identify ALL clusters in the population under 19 years of age and characterize the environment at the neighborhood level by integrating information on sources of carcinogenic exposure using spatial analysis techniques in the Metropolitan Area of San Luis Potosi, Mexico.

METHODS

Using the Kernel Density test, we designed an ecological study to identify ALL clusters from incident cases in the population under 19 years of age. A multicriteria analysis was conducted to characterize the risk at the community level from carcinogenic sources. A hierarchical cluster analysis was performed to characterize risk at the individual level based on carcinogenic source count within 1 km for each ALL case.

RESULTS

Eight clusters of carcinogenic sources were located within the five identified ALL clusters. The multicriteria analysis showed high-risk areas (by density of carcinogenic source) within ALL clusters.

CONCLUSIONS

This study has a limited source and amount of available data on ALL cases, so selection bias is present as well as the inability to rule out residual confounding factors, since covariates were not included. However, in this study, children living in environments with high vehicular density, gas stations, brick kilns, incinerators, commercial establishments burning biomass, or near industrial zones may be at higher risk for ALL.

Examining the relationship between land use and childhood leukemia and lymphoma in Tehran

We conducted a hospital-based case-control study to explore the association between proximity to various land use types and childhood leukemia and lymphoma. This research involved 428 cases of childhood leukemia and lymphoma (2016-2021), along with a control group of 428 children aged 1-15 in Tehran. We analyzed the risk of childhood cancer associated with land use by employing logistic regression adjusted for confounding factors such as parental smoking and family history. The odds ratio (OR) for children with leukemia and lymphoma residing within 100 m of the nearest highway was 1.87 (95% CI = 1.00-3.49) and 1.71 (95% CI = 1.00-2.93), respectively, in comparison to those living at a distance of 1000 m or more from a highway. The OR for leukemia with exposure to petrol stations within 100 m was 2.15 (95% CI = 1.00-4.63), and for lymphoma it was 1.09 (95% CI = 0.47-2.50). A significant association was observed near power lines (OR = 3.05; 95% CI = 0.97-9.55) within < 100 m for leukemia. However, no significant association was observed between power lines and the incidence of childhood lymphoma. There was no association between bus stations, major road class 2, and the incidence of childhood leukemia and lymphoma. In conclusion, our results suggest a possible association between the incidence of childhood leukemia and proximity to different urban land uses (i.e., highways and petrol stations). This study is the first step in understanding how urban land use affects childhood leukemia and lymphoma in Tehran. However, comprehensive studies considering individual-level data and specific pollutants are essential for a more nuanced understanding of these associations.

Exposure to residential traffic and trajectories of unhealthy ageing: results from a nationally-representative cohort of older adults

BACKGROUND

Traffic exposure has been associated with biomarkers of increased biological ageing, age-related chronic morbidities, and increased respiratory, cardiovascular, and all-cause mortality. Whether it is associated with functional impairments and unhealthy ageing trajectories is unknown.

METHODS

Nationally representative population-based cohort with 3,126 community-dwelling individuals aged ≥60 years who contributed 8,291 biannual visits over a 10 year period. Unhealthy ageing was estimated with a deficit accumulation index (DAI) based on the number and severity of 52 health deficits, including 22 objectively-measured impairments in physical and cognitive functioning. Differences in DAI at each follow-up across quintiles of residential traffic density (RTD) at 50 and 100 meters, and closest distance to a petrol station, were estimated using flexible marginal structural models with inverse probability of censoring weights. Models were adjusted for sociodemographic and time-varying lifestyle factors, social deprivation index at the census tract and residential exposure to natural spaces.

RESULTS

At baseline, the mean (SD) age and DAI score of the participants were 69.0 (6.6) years and 17.02 (11.0) %, and 54.0% were women. The median (IQR) RTD at 50 and 100 meters were 77 (31-467) and 509 (182-1802) vehicles/day, and the mean (SD) distance to the nearest petrol station of 962 (1317) meters. The average increase in DAI (95%CI) for participants in quintiles Q2-Q5 (vs Q1) of RTD at 50 meters was of 1.51 (0.50, 2.53), 0.98 (-0.05, 2.01), 2.20 (1.18, 3.21) and 1.98 (0.90, 3.05), respectively. Consistent findings were observed at 100 meters. By domains, most of the deficits accumulated with increased RTD were of a functional nature, although RTD at 50 meters was also associated with worse self-reported health, increased vitality problems and higher incidence of chronic morbidities. Living closer to a petrol station was associated with a higher incidence of functional impairments and chronic morbidities.

CONCLUSIONS

Exposure to nearby residential traffic is associated with accelerated trajectories of unhealthy ageing. Diminishing traffic pollution should become a priority intervention for adding healthy years to life in the old age.

Traffic Density Exposure, Oxidative Stress Biomarkers and Plasma Metabolomics in a Population-Based Sample: The Hortega Study

Exposure to traffic-related air pollution (TRAP) generates oxidative stress, with downstream effects at the metabolic level. Human studies of traffic density and metabolomic markers, however, are rare. The main objective of this study was to evaluate the cross-sectional association between traffic density in the street of residence with oxidative stress and metabolomic profiles measured in a population-based sample from Spain. We also explored in silico the potential biological implications of the findings. Secondarily, we assessed the contribution of oxidative stress to the association between exposure to traffic density and variation in plasma metabolite levels. Traffic density was defined as the average daily traffic volume over an entire year within a buffer of 50 m around the participants' residence. Plasma metabolomic profiles and urine oxidative stress biomarkers were measured in samples from 1181 Hortega Study participants by nuclear magnetic resonance spectroscopy and high-performance liquid chromatography, respectively. Traffic density was associated with 7 (out of 49) plasma metabolites, including amino acids, fatty acids, products of bacterial and energy metabolism and fluid balance metabolites. Regarding urine oxidative stress biomarkers, traffic associations were positive for GSSG/GSH% and negative for MDA. A total of 12 KEGG pathways were linked to traffic-related metabolites. In a protein network from genes included in over-represented pathways and 63 redox-related candidate genes, we observed relevant proteins from the glutathione cycle. GSSG/GSH% and MDA accounted for 14.6% and 12.2% of changes in isobutyrate and the CH2CH2CO fatty acid moiety, respectively, which is attributable to traffic exposure. At the population level, exposure to traffic density was associated with specific urine oxidative stress and plasma metabolites. Although our results support a role of oxidative stress as a biological intermediary of traffic-related metabolic alterations, with potential implications for the co-bacterial and lipid metabolism, additional mechanistic and prospective studies are needed to confirm our findings.

Exploring Urban Green Spaces' Effect against Traffic Exposure on Childhood Leukaemia Incidence

BACKGROUND

Several environmental factors seem to be involved in childhood leukaemia incidence. Traffic exposure could increase the risk while urban green spaces (UGS) exposure could reduce it. However, there is no evidence how these two factors interact on this infant pathology.

OBJECTIVES

to evaluate how residential proximity to UGS could be an environmental protective factor against traffic exposure on childhood leukaemia incidence.

METHODS

A population-based case control study was conducted across thirty Spanish regions during the period 2000-2018. It included 2526 incident cases and 15,156, individually matched by sex, year-of-birth, and place-of-residence. Using the geographical coordinates of the participants' home residences, a 500 m proxy for exposure to UGS was built. Annual average daily traffic (AADT) was estimated for all types of roads 100 m near the children's residence. Odds ratios (ORs) and 95% confidence intervals (95% CIs), UGS, traffic exposure, and their possible interactions were calculated for overall childhood leukaemia, and the acute lymphoblastic (ALL) and acute myeloblastic leukaemia (AML) subtypes, with adjustment for socio-demographic covariates.

RESULTS

We found an increment of childhood leukaemia incidence related to traffic exposure, for every 100 AADT increase the incidence raised 1.1% (95% CI: 0.58-1.61%). UGS exposure showed an incidence reduction for the highest exposure level, Q5 (OR = 0.63; 95% CI = 0.54-0.72). Regression models with both traffic exposure and UGS exposure variables showed similar results but the interaction was not significant.

CONCLUSIONS

Despite their opposite effects on childhood leukaemia incidence individually, our results do not suggest a possible interaction between both exposures. This is the first study about the interaction of these two environmental factors; consequently, it is necessary to continue taking into account more individualized data and other possible environmental risk factors involved.

Persistently high incidence rates of childhood acute leukemias from 2010 to 2017 in Mexico City: A population study from the MIGICCL

Introduction

Over the years, the Hispanic population living in the United States has consistently shown high incidence rates of childhood acute leukemias (AL). Similarly, high AL incidence was previously observed in Mexico City (MC). Here, we estimated the AL incidence rates among children under 15 years of age in MC during the period 2010-2017.

Methods

The Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia conducted a study gathering clinical and epidemiological information regarding children newly diagnosed with AL at public health institutions of MC. Crude age incidence rates (cAIR) were obtained. Age-standardized incidence rates worldwide (ASIRw) and by municipalities (ASIRm) were calculated by the direct and indirect methods, respectively. These were reported per million population <15 years of age; stratified by age group, sex, AL subtypes, immunophenotype and gene rearrangements.

Results

A total of 903 AL cases were registered. The ASIRw was 63.3 (cases per million) for AL, 53.1 for acute lymphoblastic leukemia (ALL), and 9.4 for acute myeloblastic leukemia. The highest cAIR for AL was observed in the age group between 1 and 4 years (male: 102.34 and female: 82.73). By immunophenotype, the ASIRw was 47.3 for B-cell and 3.7 for T-cell. The incidence did not show any significant trends during the study period. The ASIRm for ALL were 68.6, 66.6 and 62.8 at Iztacalco, Venustiano Carranza and Benito Juárez, respectively, whereas, other municipalities exhibited null values mainly for AML.

Conclusion

The ASIRw for childhood AL in MC is among the highest reported worldwide. We observed spatial heterogeneity of rates by municipalities. The elevated AL incidence observed in Mexican children may be explained by a combination of genetic background and exposure to environmental risk factors.

Cadmium (Cd) and Lead (Pb) topsoil levels and incidence of childhood leukemias

There are few well-established risk factors for childhood leukemias. While the frequency of childhood leukemias might be partially attributable to some diseases (accounting for a small fraction of cases) or ionizing radiation, the role of heavy metals has not been assessed. The objective of our study was to assess the potential association between levels of cadmium (Cd) and lead (PB) in soil and childhood leukemias incidence. We conducted a population-based case-control study of childhood leukaemia in Spain, covering 2897 incident cases gathered from the Spanish Registry of Childhood Tumours and including 14 Spanish Regions with a total population of 5,307,433 children (period 1996-2015). Cd and Pb bioavailable levels at every children's home address were estimated using data from the Geochemical Atlas of Spain. We used logistic regression to estimate odds ratios (ORs) and their 95% confidence intervals (95%CIs); we included as covariates: sex, rurality, employment rate and socioeconomic status. Metal levels were analysed according to two definitions: as continuous variable assuming linearity and as categorical variables to explore a potentially nonlinear association (quantiles). Increases in both Cd and Pb topsoil levels were associated with increased probability of childhood leukemias incidence. The results for the models with the continuous variables showed that a unit increase on the topsoil level was associated with an OR of 1.11 for Cd (95%CI 1.00-1.24) and an OR of 1.10 for Pb (95%CI 0.99-1.21). Our study may point towards a possible link between residential Cd and Pb topsoil levels and the probability of childhood leukemias incidence. Residing in a location with the highest concentrations of these heavy metals compared to those locations with the lowest could increase the risk around a 20%, for both Cd and Pb.

Exposure to Traffic Density during Pregnancy and Birth Weight in a National Cohort, 2000-2017

The variation on birth weight is associated with several outcomes early on in life and low birth weight (LBW) increases the risk of morbidity and mortality. Some environmental exposures during pregnancy, such as particulate matters and other traffic-related pollutants can have a significant effect on pregnant women and fetuses. The aim of this study is to estimate the effect of exposure to traffic density during pregnancy over birth weight in Spain, from 2000–2017. This was a retrospective, cross-sectional study using the information from Spain Birth Registry Statistics database. The traffic density was measured using the Annual average daily traffic. Multivariate linear regression models using birth weight and traffic density were performed, as well as a logistic regression model to estimated Odds ratios for LBW and GAM models to evaluate the non-linear effect. Our findings showed that increases in traffic density were associated with reduction of birth weight and increases of LBW risk. Moreover, exposure to high and very-high traffic-density during pregnancy were associated with reduction of birth weight and increase on LBW risk comparing with exposure to low number of cars trespassing the neighborhoods. The results of this study agree with previous literature and highlights the need of effective policies for reducing traffic density in residential neighborhoods of cities and towns.

Exploring Blue Spaces' Effects on Childhood Leukaemia Incidence: A Population-Based Case-Control Study in Spain

Background: Blue spaces have been a key part of human evolution, providing resources and helping economies develop. To date, no studies have been carried out to explore how they may be linked to paediatric oncological diseases. Objectives: To explore the possible relationship of residential proximity to natural and urban blue spaces on childhood leukaemia. Methods: A population-based case–control study was conducted in four regions of Spain across the period 2000–2018. A total of 936 incident cases and 5616 controls were included, individually matched by sex, year of birth and place of residence. An exposure proxy with four distances (250 m, 500 m, 750 m, and 1 km) to blue spaces was built using the geographical coordinates of the participants’ home residences. Odds ratios (ORs) and 95% confidence intervals (95%CIs) for blue-space exposure were calculated for overall childhood leukaemia, and the acute lymphoblastic (ALL) and acute myeloblastic leukaemia (AML) subtypes, with adjustment for socio-demographic and environmental covariates. Results: A decrease in overall childhood leukaemia and ALL-subtype incidence was found as we came nearer to children’s places of residence, showing, for the study as a whole, a reduced incidence at 250 m (odds ratio (OR) = 0.77; 95%CI = 0.60–0.97), 500 m (OR = 0.78; 95%CI = 0.65–0.93), 750 m (OR = 0.80; 95%CI = 0.69–0.93), and 1000 m (OR = 0.84; 95%CI = 0.72–0.97). AML model results showed an increasing incidence at closest to subjects’ homes (OR at 250m = 1.06; 95%CI=0.63–1.71). Conclusions: Our results suggest a possible association between lower childhood leukaemia incidence and blue-space proximity. This study is a first approach to blue spaces’ possible effects on childhood leukaemia incidence; consequently, it is necessary to continue studying these spaces—while taking into account more individualised data and other possible environmental risk factors.

Urban green spaces and childhood leukemia incidence: A population-based case-control study in Madrid

BACKGROUND

Childhood leukemia is the most common childhood cancer. To date, few risk factors related to predisposition have been identified; therefore, new hypotheses should be considered.

OBJECTIVE

To explore the possible relationship of residential proximity to urban green spaces on childhood leukemia.

METHODS

We conducted a population-based case control study in the metropolitan area of Madrid from 2000 to 2015. It included 383 incident cases and 1935 controls, individually matched by birth year, sex and area of residence. Using the geographical coordinates of the participants' home residences, we built a proxy for exposure with four distances (250 m, 500 m, 750 m and 1 km) to urban parks (UPs) and urban wooded areas (UWAs). We employed logistic regression models to determinate the effect of them on childhood leukemia adjusting for environmental and socio-demographic covariates.

RESULTS

we found a reduction in childhood leukemia incidence at a distance of 250 m from UPs (OR = 0.78; 95%CI = 0.62-0.98), as well as a reduction of the incidence in the Q3 and Q4 quintiles for exposure to UWAs, in the 250 m and 500 m buffers respectively (Q3 (250 m): OR = 0.69; 95%CI = 0.48-1.00; and, Q4 (500 m): OR = 0.69; 95%CI = 0.48-0.99).

CONCLUSIONS

Our results suggest a possible association between lower incidence of childhood leukemia and proximity to different forms of urban green space. This study is a first approach to the possible urban green space effects on childhood leukemia so is necessary to continue studying this spaces taking into account more individual data and other environmental risk factors.

Residential traffic exposure and lymphohematopoietic malignancies among children in the city of São Paulo, Brazil: An ecological study

BACKGROUND

Despite widespread evidence that air pollution is carcinogenic, there is little evidence from low-middle income countries, especially related to childhood malignancies. We examined the role of traffic related pollution on lymphohematopoietic malignancies among under-14 s in Sao Paulo.

METHODS

All incident cases between 2002 and 2011 were collected from a population-based registry. Exposures were assigned on residential address at diagnosis via traffic density database (for the year 2008) and a satellite derived NO₂ land use regression model (averaged between 1997 and 2011). Incidence rate ratios (IRRs) were calculated via Poisson Regression adjusted by age, gender and socioeconomic status (SES), with additional stratification by SES.

RESULTS

A positive association between traffic and NO₂ with some lymphohematopoietic malignancies was observed with the degree of effect differing by SES. For example, lymphoid leukemia IRRs in the lower SES group were 1.21 (95 % CI: 1.06, 1.39) for traffic density and 1.38 (95 % CI: 1.13, 1.68) for NO₂. In the higher group they were 1.06 (95 % CI: 1.00, 1.14) and 1.37 (95 % CI: 1.16, 1.62).

CONCLUSION

NO₂ and traffic density were associated with Hodgkin lymphoma and lymphoid leukemia among children in São Paulo. Differing IRRs by gender and SES group indicate differences in underlying risk and/or exposure profiles.

Maternal Residential Proximity to Major Roadways and the Risk of Childhood Acute Leukemia: A Population-Based Case-Control Study in Texas, 1995-2011

Acute leukemia is the most common pediatric malignancy. Some studies suggest early-life exposures to air pollution increase risk of childhood leukemia. Therefore, we explored the association between maternal residential proximity to major roadways and risk of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Information on cases with acute leukemia (n = 2030) was obtained for the period 1995-2011 from the Texas Cancer Registry. Birth certificate controls were frequency matched (10:1) on birth year (n = 20,300). Three residential proximity measures were assessed: (1) distance to nearest major roadway, (2) residence within 500 meters of a major roadway, and (3) roadway density. Multivariate logistic regression was used to generate adjusted odds ratios (aOR) and 95% confidence intervals (CI). Mothers who lived ≤500 meters to a major roadway were not more likely to have a child who developed ALL (OR = 1.03; 95% CI: 0.91-1.16) or AML (OR = 0.84; 95% CI: 0.64-1.11). Mothers who lived in areas characterized by high roadway density were not more likely to have children who developed ALL (OR = 1.06, 95% CI: 0.93-1.20) or AML (OR = 0.83, 95% CI: 0.61-1.13). Our results do not support the hypothesis that maternal proximity to major roadways is strongly associated with childhood acute leukemia. Future assessments evaluating the role of early-life exposure to environmental factors on acute leukemia risk should explore novel methods for directly measuring exposures during relevant periods of development.

Methodological approaches to the study of cancer risk in the vicinity of pollution sources: the experience of a population-based case-control study of childhood cancer

Background

Environmental exposures are related to the risk of some types of cancer, and children are the most vulnerable group of people. This study seeks to present the methodological approaches used in the papers of our group about risk of childhood cancers in the vicinity of pollution sources (industrial and urban sites). A population-based case–control study of incident childhood cancers in Spain and their relationship with residential proximity to industrial and urban areas was designed. Two methodological approaches using mixed multiple unconditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) were developed: (a) “near vs. far” analysis, where possible excess risks of cancers in children living near (“near”) versus those living far (“far”) from industrial and urban areas were assessed; and (b) “risk gradient” analysis, where the risk gradient in the vicinity of industries was assessed. For each one of the two approaches, three strategies of analysis were implemented: “joint”, “stratified”, and “individualized” analysis. Incident cases were obtained from the Spanish Registry of Childhood Cancer (between 1996 and 2011).

Results

Applying this methodology, associations between proximity (≤ 2 km) to specific industrial and urban zones and risk (OR; 95% CI) of leukemias (1.31; 1.04–1.65 for industrial areas, and 1.28; 1.00–1.53 for urban areas), neuroblastoma (2.12; 1.18–3.83 for both industrial and urban areas), and renal (2.02; 1.16–3.52 for industrial areas) and bone (4.02; 1.73–9.34 for urban areas) tumors have been suggested.

Conclusions

The two methodological approaches were used as a very useful and flexible tool to analyze the excess risk of childhood cancers in the vicinity of industrial and urban areas, which can be extrapolated and generalized to other cancers and chronic diseases, and adapted to other types of pollution sources.

Association between Outdoor Air Pollution and Childhood Leukemia: A Systematic Review and Dose-Response Meta-Analysis

BACKGROUND

A causal link between outdoor air pollution and childhood leukemia has been proposed, but some older studies suffer from methodological drawbacks. To the best of our knowledge, no systematic reviews have summarized the most recently published evidence and no analyses have examined the dose-response relation.

OBJECTIVE

We investigated the extent to which outdoor air pollution, especially as resulting from traffic-related contaminants, affects the risk of childhood leukemia.

METHODS

We searched all case-control and cohort studies that have investigated the risk of childhood leukemia in relation to exposure either to motorized traffic and related contaminants, based on various traffic-related metrics (number of vehicles in the closest roads, road density, and distance from major roads), or to measured or modeled levels of air contaminants such as benzene, nitrogen dioxide, 1,3-butadiene, and particulate matter. We carried out a meta-analysis of all eligible studies, including nine studies published since the last systematic review and, when possible, we fit a dose-response curve using a restricted cubic spline regression model.

RESULTS

We found 29 studies eligible to be included in our review. In the dose-response analysis, we found little association between disease risk and traffic indicators near the child's residence for most of the exposure range, with an indication of a possible excess risk only at the highest levels. In contrast, benzene exposure was positively and approximately linearly associated with risk of childhood leukemia, particularly for acute myeloid leukemia, among children under 6 y of age, and when exposure assessment at the time of diagnosis was used. Exposure to nitrogen dioxide showed little association with leukemia risk except at the highest levels.

DISCUSSION

Overall, the epidemiologic literature appears to support an association between benzene and childhood leukemia risk, with no indication of any threshold effect. A role for other measured and unmeasured pollutants from motorized traffic is also possible. https://doi.org/10.1289/EHP4381.