Pyridine would not have been suggested as the likely cause of the mass die off of crabs, but it was suggested in the original DEFRA report and subsequently much evidence supports pyridine as being the most likely cause.
High concentrations of pyridine were found in all the dead crabs recovered from the area. However, occasional crabs elsewhere have been found to have high pyridine levels, but not all of a population as was the case for the October 2021 die off.
New experimental work has found that pyridine is moderately toxic to crabs.
Pyridine was found 7 months after the die off by independent sampling at the River Tees sediment and the Tees Bay dredge disposal site.
Pyridine is a minor components of coal tar by-product of coke manufacture. However as millions of tonnes of coal has been processed into coke on the South Tees site over 140 years, much coal tar will contaminated the ground and its existence in tanks / gas holders / pipes was a major reason why the site was classified as a upper level COMAH site.