By Michael Cohen

This blog was originally published on Desert Health here.

This summer, the Pacific Institute, a global nonpartisan think tank, released “Breathing Hazard: Air Pollution in the Salton Sea Region,” describing and assessing complex and growing air quality threats in the valley. The Salton Sea – about 35 miles southeast of Palm Springs – is California’s largest lake and a major stopover for hundreds of species of migratory birds. The Sea has shrunk by more than 70 square miles over the past 30 years due to a 22% reduction in local agricultural water use, exposing dry lakebed—known as “playa”—and contributing to dangerous dust levels in an area already burdened with some of the highest respiratory hospitalization rates in California. 

Dust in the Valley

Local residents are quite familiar with dust, especially after flooding caused by Tropical Storm Hilary in August 2023 brought tons of sediment into the valley. The dust blowing off this sediment can coat much of the valley and reduce visibility during strong winds, causing traffic accidents and road closures. Still, our lungs typically can screen out or remove these larger dust particles from our airways. Smaller particles that are hard to see, known as PM10—roughly 1/7 the width of a human hair—pose a greater health threat. Even smaller particles, known as PM2.5, can pass through the lungs into the bloodstream, affecting the heart and other organs. In addition to the size of the particles, the chemical and biological characteristics of these tiny particles can pose additional risks to human health. And, some gases, such as ozone and hydrogen sulfide (with its characteristic rotten egg smell), also impair human health in the valley, causing breathing problems, headaches and other symptoms.

Many sources of air pollution

The new Institute report synthesizes findings from scores of academic papers and agency reports to improve understanding of what contributes to regional air pollution and how to protect public health most effectively. While the Salton Sea gets most of the blame for local air pollution and public health impacts, the report details how the problem is much larger than the Sea. Multiple sources throughout the region emit a complex mix of dust, chemicals and biological pollutants, threatening the health of more than half a million people. Dust from unpaved roads, farms and off-road vehicles in nearby deserts; the growing expanse of exposed Salton Sea lakebed; diesel emissions, ozone and smoke from agricultural and other fires, combined with contaminants originating from the Salton Sea itself (such as hydrogen sulfide), all contribute to very high childhood asthma hospitalization rates, chronic nosebleeds and other indicators of poor health. These multiple sources frequently cause local dust and ozone concentrations to exceed federal and state regulatory thresholds.

Short-term (“acute”) exposure to high concentrations of air pollution can impair public health. Yet long-term (“chronic”) exposure to low concentrations of a pollutant, even at levels not typically considered harmful, can also result in cumulative impacts that impair public health. Just as long-term exposure to low concentrations of a single pollutant can add up to a cumulative impact, the combination of many different physical, chemical and biological components of air pollution–even if they only exist in low concentrations–can also add up to a larger cumulative impact. Other factors, such as heat exposure and limited health care facilities and options in the eastern valley, can further stress human health. The combination of these many factors means that only looking at health impacts during the worst conditions can obscure the ongoing, long-term health impacts felt by many people throughout the valley.

Focusing on a different solution

Local and state agencies have invested tens of millions of dollars in targeted dust suppression projects, especially around the Salton Sea. Yet the new report finds that, in the context of the many factors leading to poor air quality in the valley, these targeted dust suppression projects are not the most cost-effective means to protect public health. Instead, the report recommends a coordinated effort between state and local agencies, public health experts, and community leaders to direct additional funding toward exposure control strategies to optimize public health benefits. Exposure control strategies—such as weatherizing homes, installing air filters, and issuing public alerts on days with poor air quality — can be more feasible and cost-effective than attempting to manage emissions at the many sources that pollute the air. Many homes, especially in the eastern Coachella Valley, can be very drafty, allowing dust and other pollutants to contaminate indoor air. For example, adding weatherstripping around doors and windows enables indoor air filters to work more effectively.

The idea of focusing on exposure control instead of source control sounds counterintuitive, more of a band-aid than solving the root cause of the problem. The challenge is that there is no single source or root cause of the problem. Not only are there multiple sources, but these sources can change over time, as weather conditions (especially wind direction) change. While we have seen significant reductions in the amount of some contaminants, such as diesel emissions from heavy trucks and mercury from the now-closed biomass plant near Mecca, the overwhelming number and distribution of pollution sources around the valley suggest that multiple approaches are needed. Protecting people where they live, work, and play can offer the most immediate and effective public health benefits, complementing other efforts, such as regulations limiting diesel emissions. 

Although air filters, weather-stripping and N95 masks certainly do not solve the air pollution problem, these methods are faster and cheaper and more effective than projects that reduce emissions from exposed lakebed but do not address the many other sources of emissions in the area. They can also offer multiple benefits beyond improving human health, including the reduction of energy costs and improved quality of life.