The visit was organised by the Heinrich Boell Foundation.
Vjeran Pirsic of the EKO-Kvarner environmentalist organisation said on Thursday that the group had established contact with the European Green Party and the NGOs Green Peace and Friends of the Earth, as well as with the European Commission's directorates-general for enlargement and environmental issues.
The hosts in Brussels were informed about the alarming cases of pollution of the environment in Sisak, Vranjic, Karlovac and other towns.
"The system of environmental protection has fallen apart and instead of protecting citizens, it protects polluters and capital," Pirsic said.
The secretary-general of the European Green Party, Juan Behrend, said that the information obtained from the Croatian delegation was worrying and that his party would soon send a delegation to Croatia to inspect the situation on the ground.