Part I – Context

Introduction

As described in the previous chapter wildfires pose enormous threats to human health (Reid et al., 2016b, Black et al., 2017b) and some populations are more sensitive to health impacts from wildfires. Pregnancy and childhood are periods of increased vulnerability to wildfire smoke owing to physiological changes in the mother during pregnancy and the rapid growth and development that occurs in the fetus during gestation, during infancy and throughout childhood. The scant literature on wildfire smoke exposure during pregnancy and childhood on health outcomes is bolstered by more abundant research on ambient air pollution.

Scope of chapter

The aim of this chapter is to provide an overview of the associations between wildfire smoke on perinatal and childhood health outcomes. Exposure assessment of wildfire smoke exposure in epidemiological studies was primarily based on exposure to a single fire event or fine particulate matter. Particulate matter, especially particulate matter less than 2.5 microns in aerodynamic diameter (PM2.5) is a component of wildfire smoke, and is frequently measured as part of routine ambient air pollution monitoring and hence is a useful and objective measure in epidemiological studies to assess the effect of exposure. Therefore, much of the evidence that we discuss is based on exposure to PM2.5 during periods of wildfire events, and the findings that we present are borrowed from the more extensive literature of ambient air pollution (including non-wildfire sources) and tobacco smoke to help inform our understanding of the potential health effects of wildfire smoke during pregnancy on adverse perinatal outcomes. More recently, studies have included more wildfire-specific metrics including smoke days from Hazard Mapping System or wildfire-specific PM2.5, but so far evidence is limited.
In this chapter, we first focus on pregnancy and the unique characteristics of the prenatal period. We present a summary of studies of wildfire exposure in pregnancy and effects on maternal and newborn outcomes such as low birth weight, preterm birth, birth defects, infant mortality and mental health outcomes of the mother. We discuss various methods used to assess exposure, ascertain outcomes and adjust for covariates in epidemiological analyses. We discuss methodological issues such as critical periods during pregnancy, seasonality, and co-exposures of stress during wildfire events.
Secondly, we focus on childhood as another critical period of exposure to wildfires. We review what is known on the effects of wildfire smoke on child health outcomes including health-service use, respiratory symptoms, and asthma. Finally, our chapter concludes by highlighting the gaps in the literature and future directions for research and policy. This area of study on wildfire exposure and health effects during pregnancy and childhood is in a nascent stage and our knowledge in this is expected to change drastically over the next several years.