The Environmental Protection Agency has said large scale illegal dumping is no longer occurring.
However, its annual highlights report for 2005 says vigilance is required against new threats such as unauthorised waste collection, backyard burning and fly-tipping.
The agency says there has been improved enforcement of environmental legislation by local authorities and significant reductions in illegal trafficking of waste to Northern Ireland and mainland Europe.
The report also says the establishment of a National Emissions Trading Registry means that greenhouse gas emissions trading for Ireland is now well established.
