Road runoff is a 'toxic cocktail' polluting UK waterways

The EA tests for pollutants from roads but does not regularly monitor runoff, prompting experts to call for enforcement measures around highway pollution and drainage

Road runoff is responsible for 18% of waterbody failures in England (86% of the country’s inland water bodies fail to meet targets). This is according to new research looking at the impact of the pollutants that gather on road surfaces during dry weather and are then pushed into waterways by rainfall.

The findings state that road runoff contains a toxic cocktail with heavy metals, including zinc, cadmium and copper, plus polycyclic aromatic hydrocarbons (PAHs) such as pyrene and benzo(a) pyrene. Microplastics and hundreds of other chemicals also routinely enter waterways in this way.

The white paper, produced by Keyline Civils Specialist, a drainage supplier to the construction industry, followed a roundtable discussion attended by influential figures from industry, academia, government and the third sector to discuss the problem.

Among the attendees was Ian Titherington, Senior Advisor on Sustainable Drainage to the Welsh Government. He said: “Since 2019, all new developments in Wales have incorporated sustainable drainage systems (SuDS) and we're realising how much of a problem we have.” SuDS are designed to be more sustainable than traditional drainage methods by managing runoff volumes from hard surfaces to reduce flooding, as well as reducing pollution.

Titherington added, “Highway pollution and drainage hasn’t much interest in the media but I think that's going to change. It has to be the public and private sector working together, including research establishments and industry contractor associations. People need to work together with government agencies and local authorities. 

“We've been talking about highway drainage for 20 years and have done very little about it. Now is the time to have targets and enforce them.”

“We know these chemicals can be neurotoxic, immunotoxic, carcinogenic as well as reproductive toxicants.”

Professor Alex Ford of Portsmouth University is an expert in aquatic toxicology. He agreed that road runoff has gone under the radar: “We know these chemicals can be neurotoxic, immunotoxic, carcinogenic as well as reproductive toxicants.

“Just like the issues with sewage discharges, the extent to which urban road runoff is having an impact on our waterways is largely unknown due to reduced environmental monitoring.

“There needs to be better forethought about these discharges near sensitive aquatic environments and tighter regulation for the inclusion and maintenance of engineering solutions.”

John Bryden, Head of Improving Rivers at environmental charity, Thames21 said that road runoff pollution was harming river health in every river the organisation had assessed.

He said: “Many rivers can now only support a limited number of pollution-tolerant species due to years of accumulated contaminants. We need urgent and comprehensive action involving both the technical solutions promoted in the recent white paper and the nature-based approaches identified by our tool. 

“Addressing this issue requires coordinated efforts from multiple stakeholders, including Defra, the Environment Agency, the Highways Agency, local authorities and charities. A collaborative approach can lead to significant progress in identifying, quantifying and mitigating road runoff pollution.”

Responsibility for monitoring water pollution in England rests with the Environment Agency (EA). In response to a BBC News freedom of information request earlier this year, the agency said it did not regularly monitor runoff, although it did test for pollutants from roads as part of its general water monitoring.

The EA said it recognised that runoff from highways and urban areas was a “serious issue”.