A toxic cocktail of damaging chemicals created by road pollution is flowing into England’s rivers and no regulator is monitoring the scale of its impact on wildlife or public health.

More than 18,000 outfalls, such as pipes, and about 7,700 soakaways managed by National Highways discharge rainwater potentially contaminated with heavy metals, hydrocarbons, microplastics and other chemicals from the main road network into rivers and on to land.