It's also suspected of causing breast cancer, birth defects and premature labor. DDT and its breakdown constituents, carried into river sediments by way of stormwater runoff, take decades to decompose. Levels in fish appear to be declining. Metals Dozens of kinds of toxic heavy metals including chromium, copper, lead, mercury and arsenic can have a wide range of health impacts, including causing neurological problems and cancer. These metals are found in sediments from past industrial pollution.
Industries continue to discharge metals into the river.
Urban runoff and airborne pollutants also contribute to metals in the river. Nutrients Nitrogen, phosphorous and ammonia from the discharge of treated municipal and industrial wastes contribute to algae blooms that can result in reduced dissolved oxygen. The Delaware River has one of the nation's highest concentrations of nutrients. But these nutrients haven't been a big problem, possibly because sediments suspended in the water may block out sunlight that algae need to grow. Concerned about the risk of these chemicals ending up in drinking water supplies, officials are taking steps to set maximum industrial discharge limits.