one or more of them should so request, with a view to drawing up lists of substances which, by virtue of their dangerous nature, should be subjected to special regulation. Such substances are principally those that are toxic, persistent or bioaccumulative. The practice of establishing lists of substbi.?=+i whose discharge into international watercourse[s] [systems] is either prohibited or subject to special regulation has been followed in a - 165 -number of international agreements and other instruments. W/ States have made the discharge of these stistances subject to special dgimeu because of their particularly dangerous and long-lasting nature. Indeed, the objective of some of the recent agreements dealing with these substarlces is to eliminate them entirely from the watercorrses in question. zp2/ (9) A detailed survey of representative illustrations of international agreements, the work of international organiaatlons, deoieions of international courts and tribunals, and other instances of State practice supporting article 23 is contained in the Fourth report of the Special Rapporteur. U/ A recent study lists 88 internatio.-11 agreements “containing substantive provisions concerning pollution of international watercourseat’. J.&&i The work 2.!w See, e.g. the 1976 C.-Avantion on the Protection of the Rhine against Chemical Pollution, United Rations, Treetv Se&-h, vol. 1124, p. 375; th8 1978 Agreement between Canada and the United States on Great Lakes Water Quality,m, note 163. See aJ.oil the Council of Europe’s draft European Convention for the protectioi? :J:.international watercourses against pollution, uwr note 1891 I article 1117, pare. S, of the Institute of International Law’s Athens Resolution on the Follution of RJvers and Lakes and Lnternationel Law, w, note 189; and art.’ ;1 2 of the International Law A6sOCi8tiOn’S 1982 Montreal Rules on Water Pollution, ILA, Emsf --Conference IMontreal. l.gu)# pp* 13, 535. The same t,pproach has also been used in the field of marine pollution.
**Analysis**
The text appears to be discussing international agreements and regulations related to the protection of international watercourses from pollution, focusing on substances that are toxic, persistent, or bioaccumulative. This suggests that the topic is related to environmental protection and the regulation of pollution, which is a key aspect of sustainable development.

**Category**
Natural resources and environment, International trade