The parents of boys at the Ajax academy De Toekomst in Amsterdam received letters last week to reassure them that from now on, not only would their children not be playing on any of the club’s 3G pitches with rubber crumb infill, but those pitches were being removed.

It was a swift response to the findings of a documentary on the Dutch public broadcaster NPO which revealed serious shortcomings in the government-sponsored research in 2006 that had declared the rubber crumb to be safe, thus beginning a 3G boom.

From 300 3G pitches in Holland 10 years ago there are now more than 2,000 of them, in a country where artificial turf and the 120 metric tonnes of rubber crumb used on each one – equating to 20,000 shredded tyres – is big business.

So much so that six Eredivisie teams – Heracles, Sparta Rotterdam, Excelsior, Roda JC, Zwolle and ADO Den Haag – have 3G pitches at their home stadiums. Now, for the first time in Holland, there are major doubts on health grounds.

What is the strongest allegation against rubber crumb, those little black pellets you find in boots, socks and on skin after a game on 3G? It is that carcinogens in the rubber could be responsible for cancer – with children the most vulnerable of all.