Take your allegation to the organisations who supply the data.
I suggest everybody's oil is dirty to xxx degree. Most countries have places to refine crude oil.
I know having visited many.
Fawley Hants.
Milford Haven, Pem.
Fort McMurray, Alberta.
Baku, Azerbaijan.
Here's a simple diagram, it appears that the "heavy, unrefined oil", not "completely cleaned" crude is a common issue world wide.
At the bottom right, big red arrow, Asphalt/Road Tar, black pipe.
So common they have a solution/use for it, called it tarmac, waste dirty oil and smallish, (they have to be small otherwise sheep rustlers hide behind them and steal too many sheep), pointy stones, and actually cover mud, gravel and concrete roads with it. It's been done for centuries.
- "Tarmacadam, a mainly historical tar-based material for macadamising road surfaces, patented in 1902
- Asphalt concrete, a macadamising material using asphalt instead of tar which has largely superseded tarmacadam"
Tarmac - Wikipedia
I'm surprised NZ road builders don't use the stuff.
Do your sheep, being driven to market or your shepherd's dogs, get stuck in it?