Normally environmentalists are trying to knock down barriers to reducing harmful emissions – but now they may want to erect them.

According to a study by NOAA and the US Environmental Protection Agency, highway barriers along roadways aimed at blocking the sound and sight of traffic from adjoining neighbourhoods may also be reducing the amount of pollutants reaching residential areas.

As part of the study, researchers released harmless “tracers”, which act as a stand-in for vehicle-related toxic pollutants such as carbon monoxide and heavy metals. They then investigated the role of atmospheric stability in real world conditions on the movement of pollutants near highway barriers. According to Dennis Finn, the lead author and a research meteorologist at NOAA’s Air Resources Laboratory in Idaho Falls, Idaho, the barriers blocked the noise and view of the vehicles and also reduced high concentrations of pollutants from those vehicles by lifting them and channelling them away from the adjoining areas.

Research shows that a variety of human health effects, including respiratory diseases, cardiovascular illness and cancer, are prevalent in areas where individuals live or work near heavily trafficked areas. However, it is difficult to measure the effect of highway barriers in dispersing pollutants that cause these health effects.

However, the researchers were able to conduct tracer studies in unstable, neutral and stable conditions to quantify their effects. They found that the barriers tended to trap pollutants in the area of the roadway itself, particularly in low wind speed conditions.