Mapping Congenital Heart Disease and the Emission of Developmental Toxicants in Alberta, Canada: A Geographic Information System Based Framework for Supporting Interdisciplinary Research and Surveillance Monitoring

• Author / Creator

  Deliwe P Ngwezi

• Background: Congenital heart disease (CHD) is a significant global public health issue affecting 1% of all live births and the most common lethal congenital abnormality in infancy. Although CHD may occur in the presence of chromosomal abnormalities, in most affected children, the cause is unknown. The role of environmental pollutants and socioeconomic status (SES) has recently received attention. I sought to explore the association of developmental toxicants (DTs) from industrial sources and the additional role of SES at neighborhood level and CHD in Alberta, Canada through an interdisciplinary multistep study.
  Objectives: 1) To track the trends of multipollutant groups of DTs emitted by industry and the trends of CHD and explore potential associations between trends of multipollutant groups of DTs and CHD in Alberta and its urban and rural regions.
  2) To investigate the potential exposure to multiple pollutant exposures on CHD development by assigning the sum of the inverse distance weighted emissions on the maternal residential postal code in urban and rural Alberta.
  3) To explore the role of neighborhood low SES and its association with CHD in urban and rural Alberta.
  4) To map the geographic regions at risk of CHD development from DT exposures and low SES and to determine where the variables collocate.
  Methods: I acquired the emissions data reported in the Canadian National Pollutant Release Inventory (n = 18 all emitted to air) and identified CHD patients born in Alberta from 2003–2010 (n = 2415). I identified three groups of emissions after principal component analysis: Groups 1, 2, and 3. I calculated yearly crude CHD and septal defect rates and tested for correlations using Spearman with the yearly sum of DT groups using amounts and the potential toxicity risk score of the emissions. I then assigned an inverse distance weighted (IDW) DT exposure to the maternal postal code and categorized the exposure into percentile distributions. I used Poisson and negative binomial regression models in urban and rural regions respectively to calculate CHD relative risks (RR) and (95% CI) for the IDW exposure and for SES variables. I finally mapped the locations with high risk for CHD which collocated with DT exposures and low SES.
  Results: Province-wide, I found associations between Group 1 DTs and CHD and septal defect rates, when using amounts (r = 0.86, CI 0.39, 0.97 and r = 0.89, CI 0.48, 0.98, respectively) and RS (r = 0.88, CI 0.47, 0.98 and r = 0.85, CI 0.36, 0.97, respectively). Rural Group 2 DTs were positively associated with septal defect rates in both amounts released and RS (r = 0.91, CI 0.55, 0.98 and r = 0.91, CI 0.55, 0.98, respectively). For IDW exposure, the adjusted RR in urban settings was 1.8 (95% CI: 1.5, 2.3) for Group 1 and 1.4 (95% CI: 1.3, 1.6) for both Groups 2 and 3. In rural postal codes, Groups 1 and 3 emissions had a RR of 2.6 (95% CI: 1.03, 7). For SES, there was a significant increased RR of CHD in the urban and rural lowest SES tertile, (RR = 1.1 (95% CI, 1.0, 1.3) and RR = 3.0 (95% CI, 1.9, 4.8), respectively). Rural postal codes with intermediate SES also had an increased RR = 1.6 (1.1, 2.5) when compared to the highest SES tertile. Maps revealed that few postal codes were exposed to very high levels of DT emissions and low SES was more randomly distributed in both urban and rural postal codes. However most of the postal codes were in fact exposed to all three DT groups. Few postal codes collocated with the three combined DT groups and SES suggesting a localized phenomenon of environmental injustice.
  Conclusions: I found a temporal decrease in emissions and CHD rates in rural regions and a potential positive association between CHD and septal defect rates and mixtures of organic compounds with or without gases. Few postal codes exposed to high levels of emissions and low neighborhood SES were independently associated with an increased risk of CHD in both urban and rural regions of Alberta. Rural postal codes with intermediate SES also demonstrated an increased risk of CHD indicating that the impact of SES maybe more complex in those regions. Few postal codes collocated with the three combined DT groups and SES suggesting a localized phenomenon of environmental injustice.

• Subjects / Keywords

  • Congenital Heart Disease
  • Industrial Emissions
  • Air Pollution
  • Developmental Toxicants

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3KW5807P

• License

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