California’s Nitrogen Problem—and the Bill that Could Fix It

Nitrogen pollution, largely driven by decades of nitrogen fertilizer leaching, has quietly poisoned air and water across California. When excess nitrogen fertilizer drains from fields, it does so as nitrate, a harmful contaminant linked to preterm births, ovarian cancer, thyroid cancer, colorectal cancer, and “blue baby syndrome.” Nitrogen pollution also fuels toxic algal blooms in California’s waterways, presenting health risks to people and pets. And it contributes to air pollution and climate change when converted into nitrous oxide, a greenhouse gas nearly 300 times more potent than CO2. Despite decades of warnings (including from California’s own agency officials), meaningful action to stop the pollution at the source has been slow to arrive. That may be about to change. 

Introduced by Assembly Member Rebecca Bauer-Kahan, Assembly Bill 2447, the Nitrogen Pollution Reduction Act, would require the State Water Resources Control Board (SWRCB) and regional boards to establish enforceable limits on nitrogen fertilizer to reduce water pollution. The act also encourages the use of sustainable farming practices, streamlined reporting for small and diversified farmers, and research and investment in safer fertilizer technologies. The SWRCB has had both the authority and the data to address nitrogen pollution from agriculture for decades but has failed to take meaningful action. AB 2447 gives the SWRCB a clear mandate to tackle nitrogen pollution at the source.  

The need for numeric limits 

Numeric limits on nitrogen pollution are not new in California. AB 2447 is modeled after the groundbreaking Agriculture Order 4.0 (Ag Order 4.0) issued by the Central Coast Regional Water Board (CCRWB) in 2021. In response to data showing increasing groundwater nitrate contamination and high rates of fertilizer application, the CCRWB updated its regulatory program with numeric limits on nitrogen fertilizer. Ag Order 4.0 set a goal of reducing nitrogen runoff to protect drinking water quality and provided a schedule for farmers to reduce their fertilizer applications and runoff to meet that goal over time. Ag Order 4.0 added deadlines and accountability to an existing regulatory program. Unfortunately, the SWRCB did not allow these limits to take effect and instead punted consideration of numeric limits to an outside expert panel.  

It is possible to grow food while meeting nitrogen limits that protect groundwater quality. Meaningful reductions in nitrogen pollution are achievable through improved irrigation practices, reductions in excess fertilizer applications, and implementation of sustainable farming practices like cover crops, buffer strips, and crop rotations. Sustainable farmers across California are growing food and protecting water. It’s these farmers who stand to benefit from a level playing field where pollution prevention is the norm, not the exception. AB 2447 would reward sustainable farmers for their stewardship and drive the transition to more climate-friendly agriculture.  

Numeric limits are necessary. To date, the state has focused on providing technical assistance and education and requiring data reporting and monitoring to reduce nitrogen pollution. While helpful, these efforts alone don’t work at the scale necessary to protect clean water and ecosystems. In contrast, the numeric limits issued by the European Union and New Zealand show they work to protect clean water.  

No more false choices 

Communities and governments bear the overwhelming costs of dealing with nitrogen pollution. Nitrate contamination forces communities to purchase bottled water, raises public health expenditures, may require water systems to invest in expensive technologies, and costs taxpayers to monitor and remedy the pollution. Additionally, cleanup costs balloon over time. Every year of ongoing nitrogen pollution into groundwater aquifers adds years, and at times, decades, to cleanup timelines. The status quo is financially unsustainable. It’s time for a shift.  

California has the tools and the science, and now it has a legislative path to stop nitrogen pollution at the source. The Nitrogen Pollution Reduction Act will require the state and farms to take feasible and science-based steps to reduce pollution. Thanks to the leadership of Assembly Member Bauer-Kahan, AB 2447 is a chance for the state to stop treating clean water as a luxury and start treating it as the basic right it has always been. Communities should not be presented with a false choice between clean water and healthy farming economies, and the experience of other countries shows that both are achievable.