Story at a glance
- Particulate matter and black soot pollution from traffic can negatively affect children’s developing organs.
- To better understand whether strategic planting of tree hedges (tredges) could cut exposure to these pollutants, researchers carried out an investigation at four primary schools in England.
- They found western red cedar tredges were able to capture nearly half of airborne black soot and around 46 percent of fine particulate matter pollution.
Selective planting of vegetation between playgrounds and roadways can significantly reduce children’s exposure to traffic-related air pollution, according to new research published in Scientific Reports.
Previous studies have documented the beneficial effects of growing up closer to nature on children’s lung health, while additional research has outlined the toll traffic-related air pollution can have on individuals’ health and medical bills.
Air pollution also poses a higher risk to children than adults because children’s organs are still developing and they have a higher breathing rate.
In the current investigation, a team of researchers in England installed trees managed as hedges (tredges) at three primary schools in 2019, while one school without any additional vegetation served as a control.
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Because different plants offer different benefits when it comes to removing particulate matter (PM) from the air, investigators compared the effectiveness of an ivy screen, a western red cedar barrier and a mixture of western red cedar, Swedish birch and an inner juniper hedge.
“Roadside vegetation can decrease airborne PM concentrations, through PM deposition on leaves, but can also increase them, by impeding airflow and PM dispersion,” authors explained. “Critical to optimizing PM removal is selection of species with high particle deposition velocity values, currently under-parameterised in most modeling studies.”
Measurements taken before and after installation of vegetation showed the school with a western red cedar tredge had 49 percent of black carbon, 46 percent of PM2.5 and 26 percent of PM1 captured.
“Western red cedar tredges work well because this species’ leaves form millions of tiny rough corrugated projections, each of which can bump into the particulates suspended in the air and ‘capture’ them in their ridges, furrows and pores,” explained co-author Barbara H. Maher of Lancaster University, England, in a statement.
“This takes them out of the local atmosphere and therefore reduces the exposure to these traffic-sourced air pollution particulates of the children and staff in the playground.”
The school with an ivy hedge did experience a significant reduction in PM concentrations, though not of black soot, while the school with the mixed tredge had fewer reductions in air pollution compared with the red cedar school.
The smooth, waxy surfaces of ivy leagues may have precluded them from being as effective as western red cedar leaves.
However, all three tredges “substantially reduced the magnitude and frequency of acute ‘spikes’ in PM and [black carbon] concentrations,” authors found.
Findings underscore the impact of selective planting in urban areas to help diminish the effects of traffic-related air pollution. “As an interim, fast and cost-effective measure (i.e., prior to policy-driven reductions of PM emissions), and for protection of brain, heart and prenatal health, careful use of roadside tredges should be considered for widespread implementation,” researchers concluded.
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