Residents opposing housing plans on land contaminated with asbestos were due to address MEPs on Wednesday.
The tests revealed contamination levels 23 times the HSE's limit
The Save Spodden Valley campaigners were set to be heard by MEPs concerned with human rights, the environment and public health.
Developers want to build 650 homes on a former factory site, in Spodden Valley, Rochdale, Greater Manchester.
Campaigner Jason Addy said their campaign was now attracting international interest.
He said the campaign had widened from trying to save woodland to the dangers of asbestos contamination.
On Tuesday residents gave a cautious welcome to apologies from MMC Estates and Countryside Properties for twice failing to tell them asbestos was found on the former Turner and Newall site.
Michael Drogan, managing director of landowners MMC Estates apologised for "confusion and concern" caused by its actions.
Developers Countryside Properties also apologised for the "miscommunication".
MMC's analysts Encia told residents at a public meeting in May no asbestos was found in heavy "crush" rubble at the site - a claim repeated in an e-mail to a Rochdale councillor.
But it failed to reveal asbestos was found in soil samples and fine rubble.
The Health and Safety Executive said on Tuesday parts of the site were grossly contaminated.
The campaign is calling on the Office of Deputy Prime Minister to hold a full public inquiry into the site.