{
  "url": "https://openlegislation.uk/surface-waters-dangerous-substances-classification-regulations-northern-ireland-1998/schedule-1",
  "json_url": "https://openlegislation.uk/surface-waters-dangerous-substances-classification-regulations-northern-ireland-1998/schedule-1.json",
  "legislation": "nisr/1998/397",
  "legislation_title": "Surface Waters (Dangerous Substances) (Classification) Regulations (Northern Ireland) 1998",
  "legislation_url": "https://openlegislation.uk/surface-waters-dangerous-substances-classification-regulations-northern-ireland-1998",
  "path": "schedule/1",
  "kind": "schedule",
  "number": "1",
  "heading": "Criteria for Classification DS1",
  "text": "The criteria for the classification DS1 are that the annual mean concentration of each substance listed in column (1) of Table 1 in samples taken from the sampling point for the waters in question in accordance with regulation 4 does not exceed the relevant limit specified in column (2) of that Table.\nTABLE 1\n(1)\n(2)\n(3)\nSubstance\nConcentration in microgrammes per litre (annual mean)\nReference method of measurement\n(1) The accuracy and precision of the method must be plus or minus 50% at a concentration which represents twice the value of the limit of determination.\n(2) The accuracy and precision of the method must be plus or minus 30%.\nAldrin\nDieldrin\nEndrin\nIsodrin\n0.01\n0.01\n0.005\n0.005\nGas chromatography with electron capture detection after extraction by means of an appropriate solvent with a limit of determination of 2.5 ng/1(1).\nCadmium and its compounds\n5 (total cadmium: both soluble and insoluble forms)\nAtomic absorption spectrophotometry after preservation and suitable treatment of the sample. The limit of determination is .25 µg/litre(2).\nCarbon tetrachloride\n12\nGas chromatography. The limit of determination is 0.1 µg/litre(1).\nChloroform\n12\nGas chromatography. The limit of determination is 0.1 µg/1itre(1).\nDDT (all isomers)\n0.025\nGas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination for total DDT is approximately 4 ng/l, depending on the number of extraneous substances present in the sample(1).\npara-para-DDT\n0.01\nGas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination for total DDT is approximately 4 ng/l, depending on the number of extraneous substances present in the sample(1).\nHexachlorobenzene\n0.03\nGas chromatography with electron capture after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1 depending on the number of extraneous substances present in the sample(1).\nHexachlorobutadiene\n0.1\nGas chromatography with electron capture detection after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1, depending on the number of extraneous substances present in the sample(1).\nHexachlorocyclohexane (all isomers)\n0.1\nGas chromatography with electron capture detection after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1 depending on the number of extraneous substances present in the sample(1).\nMercury and its compounds\n1 (total mercury: both soluble and insoluble forms)\nFlameless atomic absorption spectrophotometry after suitable pre-treatment of the sample which takes account in particular of pre-oxidation of the mercury and of successive reduction of the mercury ions Hg(II). The limit of detection must be 0.1 µg/litre(2).\nPentachlorophenol and its compounds\n2\nHigh pressure liquid chromatography or gas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination is 0.1 µg/litre(1).",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/nisr/1998/397/schedule/1",
    "retrieved_at": "2026-10-29T02:22:19.119822+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}