Monitoring of the water quality of the tributaries of the Meycauayan River System was conducted over a period of five years (1983-1988). Results of physic-chemical analyses of samples indicated the deterioration of the natural quality of the river waters. The major polluters of the rivers are the piggeries, poultries, duck farms, tanneries, slaughter houses, noodle factories and distilleries.
Adverse effect of pollutants on fishery resources resulted in the reduction in quantity and quality of aquatic life. The trend of pollution in the Meycauayan River System is worsening and may reach a point where the self-purification processes are exceeded.