Cause of impairment group				Miles threatened or impaired
Pathogens	    					157964
Sediment						125045
Nutrients						98585
Organic enrichment/oxygen depletion			84770
Polychlorinated biphenyls (PCBs)			78339
Metals non mercury					75770
Temperature						67266
Mercury							63837
Habitat alterations					62373
Flow alteration(s)					40691
Cause unknown						39187
Cause unknown - impaired biota				38997
Salinity/total dissolved solids/chlorides/sulphates 	34239
Turbidity      		 				29308
pH/acidity/caustic conditions				28566
Pesticides	   					16819
Other cause						11950
Ammonia							11768
Fish consumption advisory				9948
Total toxics	 					8999
Toxic inorganics					7879
Algal growth						5945
Toxic organics						4474
Dioxins							4321
Oil and grease						2874
Biotoxins						2150
Nuisance exotic species					1406
Cause unknown - fish kills				1371
Taste, color and odor					871
Trash 	      	     					751
Radiation						680
Chlorine						618
Noxious aquatic plants					295
Nusiance native species					127