Nevertheless, the proportion of sites with high concentrations (above 25 mg N03/1) increased over the review period. As for bacterial contamination, almost 75% of the 1 330 samples taken in 2004-06 had a faecal coliform count of zero, a marked improvement from about 52% ten years before. Even so, as much as 11% of the samples still had a faecal coliform count in excess of 10 per 100 ml, a level regarded as gross contamination. The most likely causes are land spreading of manure and poorly sited single house wastewater treatment systems. No clear trends can be discerned from the results of the EPA’s rolling five-year monitoring programme of the trophic status of 69 water bodies in 21 estuarine and coastal areas. Nevertheless, several major estuaries, predominantly in the south-east and south, have persistently displayed symptoms of nutrient enrichment since the EPA began to assess their trophic status in the early 1990s.