Highway runoff pollution: The toxic cocktail no-one wants to tackle 

While sewage and intensive farming pollution steal the media headlines, an eco-toxic cocktail of hydrocarbons, metals and plastics runs off our roads into rivers and streams when it rains. Stormwater Shepherds and CIWEM have been pulling together the evidence.

Poly aromatic hydrocarbons are nasty, toxic organic substances. They are carcinogenic; they cause mutations and deformities in aquatic organisms and they affect their ability to reproduce.

But you’ve probably never heard of them because they are the unwelcome ‘villains’ in a little-known pollution problem. These substances wash into our rivers and streams every time it rains, causing untold harm to insects and their larvae living amongst the sand and gravel.

A murky cocktail

These dark-grey polluting discharges wash into our aquatic environments in quiet corners of the countryside when heavy rain falls onto our roads and motorways. The road surfaces collect these and other pollutants as we drive around the country, going about our business and visiting our friends, unwittingly depositing microplastic tyre-wear particles, tiny bits of dust from our brake pads and the dirt and debris of everyday life.

When it rains hard, all these pollutants are washed off into the drainage network as quickly as possible to keep road surfaces safe and to keep us all going on our way. But they are washed down drains and curbs and gully pots, away into our rivers, streams, canal and groundwaters.

As the press coverage of sewage pollution and chicken manure in the River Wye is splashed across the papers, and pops up on our newsfeed, there is rarely any mention of pollution from road runoff.

That may be because it only takes place when it is raining hard and we are all tucked up in front of the telly, oblivious to the toxic cocktail rushing into the local river. Or it may be that because of a quirk in the application of the Environmental Quality Standards Directive, no-one measures the level of these pollutants downstream of road crossings. Or maybe because this problem has been firmly lodged in the too-hard box for too long and no one wants to take it out?

Time for a spotlight

But we must take it out and shine a spotlight on this problem because it is time that it took its rightful place alongside sewage and slurry as one of the biggest sources of pollution in British rivers.

That is why CIWEM is soon to publish a narrative document, describing the problem, assessing the scale of it, and presenting an array of possible solutions. The report – ‘Road runoff and the water environment’ – will explain how the regulatory framework and the regulators have overlooked this problem, conveniently side-stepping the requirement to Permit these discharges and avoiding calls to measure the extent of the problem.

Because there has been no routine monitoring of poly-aromatic hydrocarbon levels in rivers during rain events, downstream of road crossings, the severity of this problem is unknown.

But we know that urban rivers are polluted. We know that they are failing to achieve good ecological condition, or to support healthy populations of fish. And we have persuaded government to allow the water companies to invest many billions of pounds reducing sewage pollution over the next couple of decades.

So why is pollution from road runoff such an unpalatable topic?

CIWEM’s report acknowledges the size of the investment that will be needed to bring this pollution under control, but we cannot continue to turn a blind eye. Road runoff contains levels of poly aromatic hydrocarbons far above the Environmental Quality Standards, but it also contains toxic metals at levels that can kill fish and insects too, changing their behaviour so that they cannot feed properly or escape from predators.

The runoff contains many millions of microplastic tyre-wear particles too. The tyre-wear particles have only been known to be harmful for a few years, but scores of international research projects have uncovered the terrible harm that they cause, affecting humans, marine creatures, fish and the predators that eat the fish.

Tyre-wear particles are thought to be the largest terrestrial source of micro-plastics in our oceans and yet we still don’t install treatment devices to capture the pollution in road runoff. The far-reaching consequences of our failure to deal with this problem more quickly will not be known for a long-time, but it is likely that we will look back and rue the day that we chose to ignore pollution from road runoff.

Regulation needed

The CIWEM publication will bring this problem to centre-stage, alerting regulators, policy makers and highway authorities to the scale of the problem and the solutions that are all ready to be deployed across the Countries. The solutions are simple, passive devices that must be deployed in sequence like a SuDS Management Train.

Some of them are manufactured devices, manufactured in the UK by local businesses providing employment across the regions. Some of them are vegetative devices that can contribute to habitats for wildlife if they are designed and managed properly. And some of them are innovative, exciting solutions that have yet to come to market and might prove to be game-changers.

So we have no excuse to leave this horrific pollution uncontrolled any longer.

Finally, the report will emphasise the need to maintain and operate these treatment solutions properly. Road runoff carries most of its toxic waste in its suspended solids, which we can capture effectively and isolate from the natural environment.

But once we have captured it, we must remove it for treatment and disposal frequently so that the devices continue to carry out their essential role, as they were planned and designed to do, forever.

Pollution from road runoff is a massive problem, and the delivery of solutions will have a massive price-tag. We need to recognise the problem, measure the harm that it causes and then plan to deliver the solutions quickly and effectively.

Too much time is wasted on designing and considering options and too few solutions are delivered on the ground in a timely manner. We need to streamline the process, share all our learning with one another, and find a way to fund this final part of the pollution prevention equation.

That might mean a Stormwater Utility Levy, or product levies on tyres and car-parts, but one way or another, we must find a solution to this horrific, and long uncovered pollution.

Alistair Chisholm is Director of Policy at CIWEM.

Jo Bradley is UK Director of Operations at Stormwater Shepherds.