It’s Time for California to Act on Nitrogen Pollution

Plants need nitrogen to grow, but when too much is applied to agricultural fields as fertilizers, it pollutes the environment and contributes to the climate, biodiversity, and public health crises. Today, about 30 to 50 percent of the nitrogen fertilizers applied to farmlands are used by crops, and the rest is lost to the environment, causing significant and multifaceted harms. 

From a climate perspective, excess nitrogen can become nitrous oxide (N₂O), a greenhouse gas that is about 300 times more potent than carbon dioxide. N₂O is also a powerful—and the most abundantly emitted—ozone-depleting substance. Since the 1980s, N₂O emissions have increased by 40 percent, and that increase is largely attributed to agricultural nitrogen. According to the United Nations Global Nitrous Oxide Assessment, ozone depletion caused by N₂O emissions will likely increase skin cancer and cataract rates in the most highly populated regions of the world, including California. This is a significant public health concern. 

From another public health perspective, excess nitrogen also pollutes the environment when it enters groundwater aquifers as nitrate. Nitrate and nitrite contamination in drinking water supplies is harmful to public health because it can lead to preterm births and blue baby syndrome, a condition where infants are unable to intake sufficient oxygen, as well as leukemia, lymphoma, and childhood brain cancers. Between 2011 and 2019, an estimated 1,730 cases of blue baby syndrome were reported in California, primarily clustered in Central Valley regions with elevated nitrates in well water. More than 735,000 Californians, including low-income, under-resourced communities in the Central Valley, still do not have access to clean drinking water, including as a result of nitrate contamination.

This same nitrogen pollution also contributes to the growing harmful algal bloom (HAB) problem across the country, including California. When nitrogen runs off into fresh water, the nutrients feed cyanobacteria, which can then produce toxins that are harmful to people, pets, and biodiversity. These HABs can result in fish die-offs, sick pets, and children with blisters and rashes from swimming in an affected river. HABs can also compromise recreational and fishing economies, costing millions to clean up and remedy. Excess nitrogen in coastal and freshwater ecosystems also increases the frequency and magnitude of HABs—an issue that Southern California is no stranger to as the region currently experiences the worst series of marine HABs in its history. 

The solution to nitrogen pollution is simple: Stop wasting fertilizer by applying less. Unfortunately, that’s easier said than done. A program to curb nitrogen pollution by reducing fertilizer use exists in California, but the agency in charge of administering the program is not acting with the urgency required to fight the problem and protect communities from pollution.

The State Water Resources Control Board (the State Board) is California’s lead water quality protection agency. Created in 1967, the agency is tasked with using its regulatory authority to protect water quality and beneficial uses of water. It oversees nine regional boards, each of which administers its own pollution-control program. Unfortunately, for more than three decades (1967–1999), regional boards unconditionally approved agricultural discharges, including nitrogen, preventing the State Board from fulfilling its responsibility of protecting California’s water. To remedy this, the legislature passed a bill requiring regional boards to develop programs to specifically regulate discharges from agricultural lands. In response, the Irrigated Lands Regulatory Program (ILRP) was born. 

However, the program appears to have made little to no progress in protecting water quality, in large part because of the insufficient and incomplete data collected and reported to the State Board. Unfortunately, in some parts of California, the nitrogen pollution problem has only gotten worse. 

It took 20 years for the State Board to act on data collection and reporting. In 2018, it issued a precedential order requiring the reporting of data that would effectively reduce nitrogen waste—including how much nitrogen farmers were applying (nitrogen applied) and how much is absorbed by crops (nitrogen removed).

One of the regional boards, the Central Coast Regional Board, had already been collecting nitrogen application data. In 2021, it used all its nitrogen applied, nitrogen removed, and raw farmer-reported data to develop a commonsense regulation called Ag Order 4.0, which set numeric limits on nitrogen discharges to reduce wasteful fertilizer over-applications. Unfortunately, the State Board immediately remanded Ag Order 4.0, arguing the Central Coast Regional Board improperly set limits despite collecting the information the State Board required in its 2018 order. Delaying action further, the State Board created an outside expert panel to study the question of whether the data is sufficient. 

It’s been four years since the remand. The State Board completed its list of questions for the panel, but the composition is still being finalized. The panel will meet to discuss the issue this summer, and its findings could mark a key turning point for California to finally start addressing the nitrogen pollution crisis. Ultimately, it will be up to the State Board to act. 

This summer’s panel will investigate if there is enough data to recommend limits for nitrogen discharges, and, if yes, how to set those limits. 

To be successful, the panel needs a holistic understanding of nitrogen use and losses across the state to effectively answer questions about nitrogen discharge limits that protect and improve water quality. Three reports have been prepared for the panel, and unfortunately, two of the three reports fall woefully short in providing statewide nitrogen use and loss information to the panel. 

The panel hasn’t convened yet, which means there is still an opportunity to collect, collate, and share all the necessary information. All regional boards were required to collect nitrogen applied and nitrogen removed data since the 2018 order. All the regional boards also have access to the raw farmer-reported data needed to inform nitrogen discharge limits. The State Board must exert its authority to get the panel all the data collected by its regional boards since the 2018 order. If there’s an issue with data standardization across the different regions, the State Board should enlist the help of its regional boards to clean up their datasets accordingly. 

While there may never be perfect data, there is more than enough collected by several regional boards to move forward with much-needed and legally required—but decades-delayed—plans to reduce dangerous nitrogen waste. At the very least, it is crystal clear that the Central Coast Regional Board has all the information it needs to move forward with Ag Order 4.0. 

It has been 25 years since the legislature required the State Board to regulate pollution from agricultural lands, and communities still don’t have clean drinking water. This is unacceptable. We’ve shared our concerns with the two analyses referenced above with the State Board and provided ideas for additional analyses. We will continue urging the State Board and panel to use the data available to recommend limits on nitrogen pollution. The 735,000 Californians who do not have access to clean drinking water cannot afford to wait another 25 years.