The Hudson River, a 315-mile tidal estuary stretching north from New York Harbor, was historically notorious for severe industrial and municipal pollution. Decades of unregulated discharge earned the waterway an infamous reputation. Today, the river’s status is complex, reflecting a significant, decades-long recovery from its worst condition while still grappling with persistent challenges. The Hudson is considerably cleaner than it was in the mid-20th century, but recreational safety and long-term ecological health remain two distinct concerns.
Current Water Quality Metrics
The immediate safety of the Hudson River for activities like swimming and boating is assessed using key water quality indicators. A primary metric is the concentration of Enterococcus bacteria, which indicates fecal contamination from human and animal waste. The Environmental Protection Agency (EPA) recommends that the geometric mean of Enterococcus in brackish recreational waters, such as the Lower Hudson, should not exceed 35 colony-forming units per 100 milliliters (cfu/100mL).
Water quality often improves during dry weather but deteriorates rapidly following rain events, which trigger the discharge of untreated sewage. Dissolved oxygen (DO) content is another measure of ecological health, necessary for aquatic life. DO levels are generally above federal thresholds, though bottom-layer concentrations are consistently lower than those at the surface. Turbidity, or water clarity, also fluctuates, peaking after major storms when high volumes of sediment and runoff wash into the estuary.
Legacy Pollution and Long-Term Ecological Risks
The most profound long-term health issue for the Hudson River is the lasting contamination from Polychlorinated Biphenyls (PCBs), a class of toxic industrial chemicals. Between the 1940s and 1977, an estimated 1.3 million pounds of PCBs were discharged into the upper river, settling deep into the riverbed sediment. These persistent contaminants do not dissolve readily in water but are instead absorbed by organisms, leading to bioaccumulation as they move up the food chain.
The presence of PCBs in fish and crabs is the reason for the New York State Department of Health’s long-standing, stringent fish consumption advisories. For the entire stretch of the river from the South Glens Falls Dam to The Battery in New York City, the sensitive population—children under 15 and women under 50—is advised not to eat any fish or crabs. Consumption is severely limited for the general population, and advisories also exist for other legacy toxins, including mercury, cadmium, and dioxin, in certain species. This contamination poses a persistent ecological risk, as the health of the river’s wildlife and the safety of its resources are affected for generations.
Modern Sources of Contamination and Ongoing Challenges
Beyond the historical legacy, the Hudson River faces continual contamination from sources that actively enter the water today. The most significant modern source is the approximately 400 Combined Sewer Overflows (CSOs) along the river, which are remnants of old infrastructure. During heavy rainfall, these systems are overwhelmed and discharge a mix of untreated raw sewage, industrial wastewater, and stormwater runoff directly into the river.
This overflow is the primary cause of spikes in bacterial contamination, nutrient overload, and reduced dissolved oxygen levels in the river after storms. The wastewater also carries emerging contaminants, such as microplastics, which enter the river through CSOs and wastewater treatment plant effluent. These microscopic plastic fragments are a growing concern because they can be ingested by aquatic organisms and potentially carry other pollutants. Furthermore, agricultural and residential nutrient runoff, containing nitrogen and phosphorus, can fuel excessive algal growth, which depletes oxygen when the algae decompose.
Restoration Efforts and the Path Forward
The recovery of the Hudson River is an ongoing process driven by major cleanup projects, government oversight, and community action. The most notable effort was the General Electric (GE) dredging project, completed between 2009 and 2015, which removed approximately 2.75 million cubic yards of PCB-contaminated sediment from a 40-mile stretch of the Upper Hudson.
Although the dredging phase is complete, the site remains under the EPA’s Superfund program, requiring long-term monitoring and subsequent five-year reviews. Habitat restoration and environmental monitoring by GE and various governmental agencies are continuing. The path forward requires substantial investment in modernizing the outdated sewer systems to eliminate or significantly reduce the frequency of Combined Sewer Overflows. While the river has made remarkable progress, a full ecological recovery depends on continued infrastructure improvements and sustained vigilance to address both the persistent legacy toxins and the active, modern sources of contamination.