The geography of being born too small and spatiotemporal relationships with the outdoor environment

• Author / Creator

  Nielsen, Charlene

• Background: The geography of where pregnant mothers live is important in furthering our understanding of babies born too small. Many causes are suspected to restrict growth or incur premature delivery, and include prenatal exposures from natural, social, and built habitats. More research is needed on the shared hazards of the outdoor environment. Studies have identified industrial activities for exposure, but few on the actual chemicals that include developmental toxicants.
  In Canada, conditions of short gestation and low birth weight are the second leading cause of infant mortality, linked to adult chronic disease, and increasing. Also, in Canada, industrial emissions are documented by the National Pollutant Release Inventory (NPRI) and readily available for space-time analyses to better understand the contribution of ambient health hazards to babies born too small.
  Objectives: (1) Examine distributions and patterns across Canada to identify associations with outdoor environment and differences among provinces and territories; (2) Develop a multi-hazard index for Alberta to determine whether mothers living in environments with a higher accumulation of outdoor hazards had more small newborns; (3) Contrast hot spots of non-critical and critically ill small newborns; and (4) Compare hot spots of critically ill small newborns with hot spots of industrial pollutants for major Canadian cities.
  Methods: For all objectives, I classified birth records with maternal residential postal codes as small for gestational age (SGA) and low birth weight at term (LBWT). I accessed three secondary databases for all of Canada (Statistics Canada’s Vital Statistics–Births Database, 2006-2012), the province of Alberta (Alberta Perinatal Health Program, 2006-2012), and nineteen major metropolitan areas (Canadian Neonatal Network, 2006-2010). Births from the latter represented critically ill SGA (ciSGA) and critically ill LBWT (ciLBWT).
  I used publicly available spatial data on outdoor hazards (including transportation and energy infrastructure, and the NPRI chemicals emitted to air), to calculate potential exposure estimates using easily accessible spatial tools in a Geographical Information System (GIS). Main methods that I applied were kernel density, focal statistics, overlay, and space-time pattern mining, which involved creating space-time cubes from locations and birthdates, then statistically categorizing emerging hot spot patterns. To model monthly chemical emissions from the NPRI, I developed a simple wind-directed dispersion mapping technique. For the statistical associations, I used correlation and logistic regression, with covariates on area-level socioeconomic status (SES), land use, nitrogen dioxide (from an existing land use regression model), traffic, maternal age, migration, sex, urban, total number of births, and season.
  Results: Provinces and territories showed higher percentages of SGA and LBWT where there were more industrial emissions; however, there were more associations with land hazards (dumps/waste depots, gas stations, powerlines, and transformer stations). For the province of Alberta, the chemical emission-weighted index was associated with SGA and LBWT, but individual chemical emissions provided complementary information, especially sub-provincially. The emerging hot spots identified where there were more small newborns in space and time and revealed scattered areas throughout Calgary and Edmonton. The non-critical and critically ill hot spots were not located in the same areas of each city. Low SES was associated with SGA and LBWT, industrial land use was associated with ciLBWT, and no associations with ciSGA. Among all major cities, the larger ones had more and larger areas of hot spots of ciSGA. Seventy-eight wind-directed industrial chemical hot spots were associated with ciSGA hot spots. The greatest number of positive associations were observed for 28 different pollutants, mostly in Edmonton, Halifax, Montréal, Toronto, Vancouver, and Winnipeg. Of the identified industrial chemicals, many are suspected or known developmental toxicants, including ammonia, benzene, carbon monoxide, methyl ethyl ketone, particulate matter, heavy metals, and VOCs.
  Conclusions: More industrial chemicals were discovered to be related to small newborns when the study areas were smaller (i.e. sub-provincial administrative units or metropolitan areas) and each area had a unique chemical signature. My focus was on the outdoor environmental habitat because it is a public source of exposures susceptible to regulation. I hope that my research may assist everyone connected to health – from medical professionals to policy makers – to understand potential impacts the environment has on early life, learn what location-based variables may be associated, inform the public that where they live is important to their future family health, and implement preventive interventions.

• Subjects / Keywords

  • adverse birth outcomes
  • GIS
  • children's environmental health
  • air pollution

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3FN1177R

• License

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