First study of its kind shows road pollution is contaminating rivers

• New research identifies London roads making highest contribution to river pollution and poor water quality
• Findings will allow road owners and operators - such as Highways England, TfL and local highways authorities - to target key stretches of roads with the highest potential to pollute.

Pollution from the surface of London’s roads is posing a significant risk to rivers in the capital, a pioneering new study has found.

Research funded by City Hall, Transport for London and the Environment Agency found that all of the roads involved in the study have the potential to damage local rivers. Modelling has shown that roads where heavy goods vehicles (HGVs) regularly apply their brakes are often the worst affected, usually around junctions, roundabouts and traffic lights. The most polluting roads identified in the study include:

Junction of North Circular (A406) and Abbey Road, Alperton

• North Circular at Chingford
• Slip road to the A40 (B456) by Ealing Sports Ground
• Jenkins Lane, Beckton

This is the first time that dedicated research has been carried out to identify sources of this specific type of pollution, known as road run-off. Road run-off occurs when pollutants that settle on the surface of the road - such as residue from oil spills, as well as tyre and brake wear from vehicles - build up during dry weather and are then washed into rivers and streams when it rains. The problem is likely to increase with the effects of a changing climate.

Toxic metals, hydrocarbons found in fuel and other pollutants washed into water pose a significant threat to river health. Road run-off can carry over 300 pollutants, causing short and long-term damage including killing fish and even discolouring water turning the river water black.

Many of London's rivers are polluted, with only one of London’s 41 bodies of water (the Carshalton Arm, source of the River Wandle) classed as ‘good’ under the EU Water Framework Directive. The River Brent, spanning almost 18 miles, and the River Lea, spanning 42 miles, are likely to be the worst affected by polluted road run-off.

Whilst the Mayor has no direct powers over water quality, his team at City Hall has been working with partners on this new research to help drive action, including using sustainable drainage - such as planting vegetation - and creating wetlands to help filter out the worst pollutants before they reach our rivers.

These solutions also provide other benefits including reducing flood risk, greater biodiversity and improving air quality.