A kerosene spill that entered an underground surface-water drain near Treforest has spread along nearly four kilometres of the River Taff, Natural Resources Wales said on Sunday, leaving a petroleum smell across valleys communities from Glan-y-Llyn and Taff's Well to Gwaelod-y-garth and Tongwynlais.
How the pollution moved
NRW first received reports of a strong fuel odour on Friday evening, 16 October. Officers working with South Wales Fire and Rescue Service traced the pollutant to kerosene — the paraffin-style oil used in many home heating tanks — flowing through a culvert into a tributary of the Taff. By Saturday night the agency estimated about four kilometres of the main river channel showed impact, although the volume reaching open water had "reduced significantly" since the first surge.
Local residents told BBC Cymru Fyw the river carried a visible sheen and smelled like a petrol station for days. Eurig Thomas, who lives in Taff's Well, said the fumes hit as soon as he opened his door on Friday afternoon and that the slick on the water was obvious even after the strongest smell began to fade. Another resident, Sarah Llewellyn, said she had barely slept since the leak and described the scene as a "national disaster" for a village named after the river itself.
On-site response
Fire crews installed fuel-collection equipment at the drainage outfall to catch kerosene before more reached the Taff, while NRW staff placed absorbent materials in the channel. The agency said it could not confirm the precise source of the release until its investigation concludes, but that work to stop pollution at the drainage system was continuing through the weekend.
Early estimates discussed in Welsh-language coverage suggested up to 25,000 litres might have escaped, though NRW stressed that figure was not final. A former hazardous-materials officer told BBC Wales that incidents of this scale can take months or years to fully remediate, and that wildlife along the affected stretch could suffer until the sheen clears.
Health advice
Public Health Wales urged people living near the polluted reaches to keep doors and windows closed while the smell persists, avoid contact with river water in affected stretches, and wash skin with soap and water if kerosene splashes on them. The agency said brief skin contact is unlikely to cause serious harm but that anyone feeling unwell should call NHS 111 Wales.
Recreational users of the Taff Trail faced disruption separately on Sunday after South Wales Police lifted a cordon near Aberfan, where officers had investigated a suspicious item reported on Saturday. That incident was not linked to the spill, but it added to a tense weekend along a river corridor that supplies drinking water downstream toward Cardiff.
What regulators watch now
NRW is sampling water to measure ecological damage and will decide on enforcement once the source is confirmed. For households that rely on the Taff for fishing and walking, the immediate question is how long the sheen and solvent smell will linger once the drainage leak is fully sealed — and whether any tank or industrial connection upstream of Treforest faces prosecution for letting heating oil into a system that was never built to carry it.