The Environment and Heritage Service estimates that a minimum of 250,000 tonnes of household waste from the Republic of Ireland has been illegally disposed of in Northern Ireland since 2003. Given the clandestine and criminal nature of the activity, it is impossible to accurately quantify the extent of this activity on an annual basis. Material illegally landfilled in the period 2003-06 is still being discovered. To date, over 50 illegal landfill sites have been discovered in Northern Ireland containing waste originating from the Republic of Ireland.