Urban air and noise pollution in sub-Saharan Africa: A study of prenatal exposures, birth outcomes and sleep disturbances in infants
Raphael E Arku
University of Massachusetts, Amherst
Urban growth in Sub-Saharan Africa (SSA) is largely unplanned and marked by significant environmental pollution. The few measurement studies in the region show that air and noise pollution, which come from diverse sources, are now a major growing public health concern in cities. The diversity of sources in SSA cities influences the air pollution mixture and noise levels, creating large exposure disparities in relation to spatial and socioeconomic factors, with potentially huge impacts on health inequalities and by socioeconomic status (SES). Yet, there is little information on urban air and noise pollution impacts in the SSA setting to support policy and behavioral decisions.
Environmental pollution affects children in uniquely damaging ways, including death in infancy, and presents future health and socioeconomic risks to survivors. Adverse birth outcomes (particularly preterm birth [PTB] and term low birthweight [LBW]) and lower respiratory infections (e.g. pneumonia) are among the leading causes of child mortality globally, and SSA is one of the worst affected regions. Unlike high-income settings, air pollution in SSA has a complex mix of local and regional sources (e.g. traffic, biomass use, crustal dust from regional dust storms). Also, the underlying population (mostly young), disease prevalence and other health risk factors (e.g. poor sanitation and nutrition) and urbanization trends in SSA differ compared with other settings. Noise pollution from same/related sources/factors is on the rise in SSA cities and may impact child growth and development through pathways like stress and sleep disturbance; sleep is a critical health outcome, related to immune health, mental health, and cognitive function in early childhood. Despite the differences in exposure and additional risks, the evidence of associations between air and noise pollution exposures with adverse birth outcomes, and sleep health in early childhood are mostly from populations in exposure settings quite different from those in urban SSA. Lack of data in this population represent a major gap in our knowledge and a barrier to the formulation and evaluation of policies to reduce environmental exposures in the region.
This proposal aims to fill this gap by quantifying the effects of long-term maternal and early prenatal exposures (annual and seasonal averages) to PM2.5, NO2, and environmental noise pollution on PTB, term birthweight (TBW) and LBW, and on respiratory infections and sleep disturbance (quantity and quality) in infants in Accra, Ghana. The emphasis here is on providing locally sound and globally relevant data on prenatal and early postnatal exposures and child survival and developmental outcomes in the SSA context, where exposures are high and vary widely, but with little epidemiologic data. This work builds on an ongoing study by the PI, collecting large-scale field data (PM2.5, NOx, sound, and weather variables, and street-level time-lapse images) in Accra. With mentorship and expertise of a highly accomplished multidisciplinary team along with existing local research infrastructure, exposure, and proof-of-principle preliminary birth data, this proposed research will execute the following specific aims:
Aim 1: To quantify associations between prenatal exposure to PM2.5, NO2, and noise (LAeq24hr, Lday, Lnight) pollution and preterm birth, term birthweight, and term low birthweight in Accra, Ghana. Hypothesis: Urban air and noise exposure will be independently associated with PTB and TBW, and differentially by season. Leveraging high mobile phone penetration in the city, we will follow 1320 pregnant women through 24 months after birth. We will assign exposures using land use regression (LUR) models (validated in 15% homes, n=~200) and assess their associations with the outcomes.
Aim 2: To determine the effect of prenatal and early postnatal exposure to PM2.5, NO2, and noise (LAeq24hr, Lday, Lnight) pollution on sleep disturbances (quality and quantity) in infants and toddlers aged 3-18 months. Hypotheses: Chronic prenatal and early postnatal air and noise exposures will have effect on sleep quality and quantity in infants and toddlers. The 200 infants (50% girls) in the 15% homes in Aim 1 will wear the Philips Actiwatch between ages 3 and 18 months to measure sleep duration and efficiency for analysis with exposure data and differentiated by season
Aim 3: To evaluate the effect of long-term maternal exposure to PM2.5 and NO2 on lower respiratory infections in infants. Hypothesis: Urban PM2.5 and NO2 pollution will increase the risk of lower respiratory infections in infants with differential effects by season. In the same 15% infants in Aim 2, we will evaluate the role regional and local influences on air pollution play in respiratory infections in infants.
As urbanization in SSA continues at pace (increased by over 400% since 1980) to about 450 million people in 2017, local data on exposure and health effects of air and noise pollution, and the role of SES, are urgently needed to enable behavioral and local policy efforts to be evidence-based, designing interventions to protect population health, especially children who are among the most vulnerable.