Population co-exposure to extreme heat and wildfire smoke pollution in California during 2020

Abstract

Excessive warming from climate change has increased the total wildfire burned area over the past several decades in California. This has increased population exposure to both hazardous concentrations of air pollutants from fires such as fine particulate matter (smoke PM2.5) and extreme heat events. Exposure to PM2.5 and extreme heat are individually associated with negative health impacts and recent epidemiological evidence points to synergistic effects from concurrent exposures. This study characterizes the frequency and spatial distribution of co-occurring extreme heat and smoke PM2.5 events in California during the record-setting wildfire season of 2020. We measure exceedances over extreme thresholds of modeled surface-level smoke PM2.5 concentrations and heat index based on observed temperature and humidity. We estimate that, during the studied period, extreme smoke and heat co-occurred at least once within 68% of the State’s area (~288,000 km2) and an average 2.5 times across all affected areas. Additionally, 16.5 million people, mostly in lower population density areas, were impacted at least once in 2020 by such synergistic events. Our findings suggest that public health guidance and adaptation policies should account for co-exposures, not only distinct exposures, when confronting heat and smoke PM2.5.

The mental health and well-being effects of wildfire smoke: a scoping review

“…The authors hypothesized that poorer quality and older construction and lack of air conditioning, all related to lower socioeconomic status, were associated with these higher rates of indoor air pollution. Rural and Indigenous communities are also at heightened risk for health and well-being impacts of exposure to wildfire smoke [ 21 , 22 ] possibly due to closer proximity to wildfires [ 23 ], longer residential tenure in smoke-exposed geographies, reduced access to services, and higher levels of comorbidities [ 24 ]. In Canada, approximately 60% of First Nation reserves are located within regions that are at high risk from wildfire events [ 25 ].…”

Exploring spatial heterogeneity in synergistic effects of compound climate hazards: Extreme heat and wildfire smoke on cardiorespiratory hospitalizations in California

“…Since most heat index algorithms produce numerically similar results, we choose the National Weather Service’s Weather Prediction Center’s adaptation of the Rothfusz regression model for heat index calculation ( 71 , 72 ). To avoid implausible threshold values, we also replaced ZCTA-specific threshold values higher than 105°F or lower than 80°F with absolute cutoff values of 105°F or 80°F to define extreme heat days ( 46 ). Details and codes of the implementation of this algorithm in Google Earth Engine were reported elsewhere ( 46 ).…”

“…Extreme heat exposure is also expected to increase, and projections show that the frequency of extreme temperatures will increase by 10-fold in many California regions ( 44 ). Approximately 68% of the state of California was exposed to both extreme heat and wildfire smoke particulate matter concurrently during the 2020 wildfire season, and these co-exposures are expected to continue increasing under climate change ( 45 , 46 ).…”

Assessment of Regional Nursing Home Preparedness for and Regulatory Responsiveness to Wildfire Risk in the Western US

“…10 Direct exposure to heat and particulate matter from wildfire episodes places residents at heightened risk of morbidity and mortality. 11,12 Moreover, inadequate nursing home preparedness for wildfires may contribute to resident abandonment and evacuation to non-health care settings. [13][14][15] In this study, we assessed whether emergency preparedness by US nursing homes, as measured by adherence to CMS standards, is commensurate with facilities' risk of wildfire exposure.…”

“…Ensuring that nursing homes are prepared to respond to surrounding environmental hazards will become increasingly important if the frequency of community exposure to wildfires continues to increase, as has been projected . Direct exposure to heat and particulate matter from wildfire episodes places residents at heightened risk of morbidity and mortality . Moreover, inadequate nursing home preparedness for wildfires may contribute to resident abandonment and evacuation to non–health care settings …”