The Convention for the Protection of the Marine Environment of the North-East Atlantic know as the OSPAR Convention 1998 (Oslo Convention 1972 and Paris Convention 1974), is an agreement signed by a number of European countries (including the United Kingdom) to protect the quality of the North East Atlantic. The objective of the OSPAR Convention is to take all possible steps to prevent and eliminate pollution entering the sea. The OSPAR Convention provides standard methods for estimating the inputs of selected pollutants to the sea by using fixed sampling schedule and a standard input calculation. In Wales, all principal rivers are sampled monthly (12 times a year) just upstream of their tidal limits. For those rivers carrying the heaviest contaminant loads the sampling frequency maybe increased beyond the minimum of 12. Major trade effluents and sewage effluents to estuaries or coastal waters are also sampled monthly to assess direct discharges to marine waters. Flow values of discharges direct to estuary or sea are sometimes provided by the operators themselves. This is usually part of statutory monitoring arrangements. The aim of these programmes is to assess the level of contamination entering the sea from Wales (the 'load') and to chart the progress in the reduction of this load. This dataset contains the results and data obtained from these programmes.