Scientists at UC San Diego, San Diego State University and colleagues find that extreme heat and elevated ozone levels, often jointly present during California summers, affect certain ZIP codes more than others.
Those areas across the state most adversely affected tend to be poorer areas with greater numbers of unemployed people and more car traffic. The science team based this finding on data about the elevated numbers of people sent to the hospital for pulmonary distress and respiratory infections in lower-income ZIP codes.
The study identified hotspots throughout the Central Valley, areas of San Diego County east of downtown San Diego, and places like San Bernardino, where Los Angeles basin smog is often trapped by surrounding mountain ranges, among others.
Results appear the week of May 24 in the journal Proceedings of the National Academy of Sciences. The Office of Environmental Health Hazard Assessment, a division of the California Environmental Protection Agency, funded the research.
“This information can be used to activate measures to protect populations in areas which we know will be at increased risk of experiencing a health burden from these co-occurring environmental events and maximize public health benefits,” said study lead author Lara Schwarz, a graduate student who is in a joint doctoral program at San Diego State and the Herbert Wertheim School of Public Health and Human Longevity Science at UC San Diego.
In places like California, these public health hazards are expected to appear in unison more frequently as the climate continues to warm and heat waves become more prevalent and long-lasting. The study could enable more targeted public health efforts because of its unprecedented consideration of two common hazards in tandem and its relatively high-resolution breakdown of where they are most likely to cause problems. Previous studies had tended only to evaluate city- or regional-level health trends.
“Understanding the health impacts of compounding environmental events such as extreme heat and various air pollutants like tropospheric ozone becomes a priority in a changing climate,” said study co-author Tarik Benmarhnia, a climate change epidemiologist with appointments at UC San Diego’s Scripps Institution of Oceanography and Herbert Wertheim School of Public Health and Human Longevity Science. “Such events are more frequent, intense and tend to co-occur, potentially creating synergistic effects on population health impacting the most vulnerable communities.”
The work could inform early warning systems and prioritize resources more efficiently than at present, the researchers said.
Ozone, a gas and a variant molecular form of oxygen, is formed in the lower atmosphere by the reaction of various hydrocarbons to sunlight, especially during hot days. Car exhaust produces such hydrocarbons. Ozone can exacerbate asthma and other respiratory conditions among vulnerable people and is more prevalent in urban areas with more traffic.
Extreme heat can similarly affect respiratory health by itself or in combination with high ozone levels.
Schwarz’s team notes that vulnerability to the excessive heat/ozone combination seems to be diminished in wealthier ZIP codes and correlated results with factors that include better access to healthcare, lower stress levels, and more exercise.
“When considering the ZIP code level, certain areas observed strong joint-effects,” said the study authors. “A lower median income, higher percentage of unemployed residents and exposure to other air pollutants within a ZIP code drove stronger joint-effects; a higher percentage of commuters who walk/bicycle, a marker for neighborhood wealth, showed decreased effects.”
Besides Schwarz and Benmarhnia, authors include Kristen Hansen of the Herbert Wertheim School of Public Health and Human Longevity Science at UC San Diego, Anna Alari of Sorbonne University in Paris, Sindana Ilango of the University of Washington, Nelson Bernal of the University of Brasilia in Brazil, Rupa Basu of the California Environmental Protection Agency, and Alexander Gershunov of Scripps Institution of Oceanography at UC San Diego.
About Scripps Oceanography
Scripps Institution of Oceanography at the University of California San Diego is one of the world’s most important centers for global earth science research and education. In its second century of discovery, Scripps scientists work to understand and protect the planet, and investigate our oceans, Earth, and atmosphere to find solutions to our greatest environmental challenges. Scripps offers unparalleled education and training for the next generation of scientific and environmental leaders through its undergraduate, master’s and doctoral programs. The institution also operates a fleet of four oceanographic research vessels, and is home to Birch Aquarium at Scripps, the public exploration center that welcomes 500,000 visitors each year.
About UC San Diego
At the University of California San Diego, we embrace a culture of exploration and experimentation. Established in 1960, UC San Diego has been shaped by exceptional scholars who aren’t afraid to look deeper, challenge expectations and redefine conventional wisdom. As one of the top 15 research universities in the world, we are driving innovation and change to advance society, propel economic growth and make our world a better place. Learn more at ucsd.edu.