Andrew Kibble of Public Health Wales said: “It is unlikely that anyone exposed to the diesel for a short period of time will have any adverse health effects, but it is still sensible to avoid contact with diesel or the water in contaminated areas.
“Diesel can produce vapours which are odorous. Odours are generally noticeable at concentrations well below those that cause harm, but high concentrations can cause dizziness, drowsiness and headaches. If you encounter odours move away from the area and into fresh air.
“If anyone gets diesel on their skin, they should remove any affected clothing and wash using soap and water and if they feel unwell seek medical attention.
“We would also advise that all pets are kept out of contact with the diesel and that members of the public do not pick up any birds or other animals affected by diesel from the shoreline.”