By Todd Woody | Bloomberg
Californians exposed to both extreme heat and wildfire smoke on the same day run a greater risk of hospitalization for cardiorespiratory illness than from either threat alone, according to a new study.
High temperatures can trigger heart attacks and strokes, while particulate matter in wildfire smoke is linked to cancer and lung disease. Low-income communities of color are particularly vulnerable to this double-barreled threat driven by climate change, according to the paper published Friday in the journal Science Advances.
“We need to start thinking about developing strategies that consider these two hazards at the same time,” said Tarik Benmarhnia, a co-author of the paper and an associate professor at the Scripps Institution of Oceanography at the University of California at San Diego. “We need to deal with extra heat and also smoke exposure because this is going to become more and more frequent in the context of climate change.”
Scientists at UC San Diego and the University of California at Los Angeles analyzed satellite and monitoring data for 995 zip codes that account for 66.8% of the state’s population. They tabulated the number of days between 2006 and 2019 when those areas experienced either excessive heat, wildfire smoke or both.
The researchers then correlated those incidents with state data on hospitalizations for cardiorespiratory conditions in those communities. They used an epidemiological statistical technique called “relative excess risk due to interaction” to estimate the health consequences of heat waves and wildfire smoke.
“Hospitalizations on days with concurrent extreme heat and wildfire smoke events exceeded the combined hospitalizations from days with either hazard,” the paper stated.
The data showed that zip codes with higher exposure risks tended to be concentrated in the northern mountains and the Central Valley, which is ringed by forested ranges that have burned repeatedly in recent years. Overall, though, the impact of extreme heat and wildfire smoke varied across the state, reflecting California’s diverse geography of mountains, valleys and coastal plains as well as a vast wealth gap.
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“This study is the first step to understanding what social factors are making a community more at risk for these climate hazards,” said Lara Schwarz, a co-author of the paper who was a doctoral student at UC San Diego at the time of the research. “In general, we see that zip codes where communities are less educated, have a higher proportion of minorities and have a lower income are more impacted by the compounded effects of wildfire smoke and heat.”
The paper noted that such neighborhoods tend to be more densely populated and have less tree cover, which exacerbates the heat island effect. Homes in those communities are also less likely to have air conditioners that would allow for both cooling and keeping windows shut to wildfire smoke. Schwarz said that even if homes are equipped with AC, the state’s skyrocketing electricity rates can make running it prohibitively expensive.
The study’s findings underscore the need for policymakers and government officials to coordinate early-warning systems for heat and smoke, Schwarz said, focusing relief efforts on disadvantaged communities. That might mean setting up shelters that can double as cooling centers and clean-air spaces.
“This is not something that is impacting everybody or all communities in the same way and there are a lot of environmental justice implications,” said Benmarhnia. “This is a new reality that these two types of extreme events, heat and wildfires, are going to coincide and we need to be ready.”
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