Introduction
Nonpoint source (NPS) pollution refers to pollution sources that do not emerge from a single point of origin, which stands in contrast to point source pollutants where there is a single identifiable source of the pollution. Pollutants coming from NPS are generally carried by stormwater run-off, and some common industries such as agriculture, mining, and urban development. Examples of NPS pollutants include excess fertilizers and herbicides, oil, grease, and bacteria from human and animal waste. While the exact sources of NPS cannot be identified, scientists have developed systems to reduce pollution in environments that create a high volume of pollution (ex. urban areas, agricultural operations, marinas). Examples include buffer strips that absorb pollutants before they reach the water, retention ponds that capture runoff and stormwater, and sediment fences that filter pollutants and slow runoff.
Implications for Human and Environmental Health
NPS is responsible for a host of damaging effects on environmental and public health. One example is eutrophication. Certain forms of NPS, such as agricultural run-off, create an overabundance of nutrients in bodies of water. Algae feed on these nutrients and become algae blooms, which block sunlight and can sometimes release toxins. The dissolved oxygen in the water is consumed as the algae are decomposed by bacteria. When the oxygen is removed, it makes it difficult for fish and other aquatic organisms to breathe, creating what is called a “dead zone” because so few life forms are able to survive in areas with such low oxygen levels. The Gulf of Mexico has the largest dead zone in the United States; this 6,500 square mile area has been created due to NPS pollution from the Mississippi River Basin. The high nutrient levels and algal blooms associated with dead zones have harmful community effects, such as releasing toxins into drinking water that in turn cause illness for humans and animals.
NPS affects not just the ecosystem, but also the economy. If pollution causes mass die-offs and dirty-looking water, then the jobs, tourism, and recreation that rely on the waterways may experience financial losses. Human health is also at risk. For example, urban runoff carries bacteria and viruses due to improper sewage treatment, which contaminates drinking water sources and can even result in severe human illness. One common bacteria found in NPS pollution is Escherichia coli (E. coli), which is associated with human and animal waste. A major source of E. coli in urban and suburban areas is pet waste that is left on lawns and then washed into sewers and waterways. E. coli can lead to human illnesses such as diarrhea, urinary tract infections, pneumonia, and other respiratory illnesses.
Current Policies and Responses
United States
In the United States, there are initiatives at the national and state level to address NPS. Nationally, the USDA runs the Environmental Quality Incentives Program, a voluntary conservation program. Through this program, the USDA provides both financial and technical assistance to farmers to help them address concerns about natural resource management and create environmental benefits. Another federal program that addresses NPS pollution is the EPA’s 319 Grant Program for States and Territories. The 319 Grant Program was established under the Clean Water Act and provides funding for state efforts to reduce nonpoint source pollution. One limitation of this program is that the EPA has no regulatory authority over the programs created by the states and must rely heavily on their voluntary participation. However, a benefit is that each state can use these funds to craft an approach that best fits its particular context.
California’s NPS programs are directly funded by the 319 Grant Program. One example is the Porter-Cologne Act, the central law regarding water quality in the state. This policy regulates all activities and factors that could affect water quality and declares that the state can exercise its full power and jurisdiction to protect the water and prevent degradation. To continue combatting NPS, California is instating the 2020-2025 Nonpoint Source Program Implementation Plan. It aims to reduce NPS pollution through waste discharge requirements, create a grant program focused on controlling NPS, and continually evaluate the success of the NPS Program through tracking activities and water quality improvements.
Overall, NPS programs in the US have had mixed success. A federal review of the 319 Grant Program found that state programs have not reliably yielded measurable water quality improvements and some of the funds were not effectively implemented or were not clearly linked to water quality improvements. Limitations include budget constraints, which have led states to prioritize the most cost-effective projects instead of simply the most effective projects, and inconsistent levels of EPA involvement and support in state programs. Despite this, the 319 Grant Program has reduced agricultural runoff of sediment, nitrogen, and phosphorus.
China
Within the international community, China takes a markedly different approach to NPS prevention. While many US policies are aimed at state and local levels, NPS policies in China are focused on the national level. For example, China’s Ministry of Agriculture and Rural Affairs started implementing new policies around NPS prevention in 2015, including water-saving agriculture practices and a “zero-growth” action plan for regulating fertilizer and pesticide application. These policies have been successful in decreasing the amount of NPS pollution in China from 2016 to 2020. While these policies have been achieving their goals, there are additional areas to continue addressing NPS. One area of potential is in China’s new national emissions trading scheme, where the trading between point source and nonpoint source pollution can trigger the adoption of new techniques and methods for the proper production and management of natural resources. This program is still in the early stages of development but shows potential, as the market behaviors associated with NPS have been untapped in reducing pollution.
Future of NPS
The effects of NPS pollution will likely be exacerbated by climate change, which is predicted to cause more frequent and intense rainstorms. Rain will fall more frequently and in new parts of the world on infrastructure not built to withstand this amount of water, leading to polluted runoff. This runoff as well as potential sewer overflows would contribute to a great increase in NPS pollution and negative effects on human health.
However, a number of new technological advances and policies may help control and prevent further pollution. These include the refinement of practices to reduce the application of nitrogen and phosphorus, the use of ecological ditch systems to remove agricultural runoff, and end treatment technologies that remove pollutants from waterways. Many of these technologies show promise for controlling nonpoint source pollution.
