Co-exposure to planned power outages and wildfire PM2.5 and acute healthcare utilization in California: A time-stratified case-crossover study
Lauren Blair Wilner, Caitlin G. Jones-Ngo, Chen Chen, Bethany Kwoka, Vivian Do, Joel D. Kaufman, Laura C. Myers, Tarik Benmahrnia, Joan A. CaseyBackground
To prevent wildfires, electric utilities may preemptively de-energize power lines (public safety power shutoffs [PSPS]). These PSPS events may unintentionally harm health, particularly for those with pre-existing conditions like chronic obstructive pulmonary disease (COPD) or who rely on electricity-dependent medical equipment. Health impacts may worsen further if a wildfire occurs despite the power shutoff. To assess the effect of PSPS events, wildfire fine particulate matter (PM 2.5 ) exposure, and their co-occurrence on cause-specific healthcare utilization.
Methods and findings
We identified PSPS events in California from 2013 to 2019, categorizing magnitude based on number of people without power by zip code. We leveraged zip code-level average daily wildfire PM 2.5 estimates and respiratory, COPD-specific, cardiovascular, and psychiatric emergency department visits and unscheduled hospital admissions among adults aged 20+ from the California Department of Health Care Access and Information. Using a time-stratified case-crossover design, we estimated the impact of same-day and lagged PSPS events alone, wildfire PM 2.5 alone, and their co-occurrence on healthcare utilization, adjusting for daily temperature.
Severe PSPS events were associated with elevated odds of same-day respiratory encounters (OR = 1.06, 95% CI: 1.02, 1.11) and lag 0–3 effects were similar. These associations were stronger for COPD. Compared to no PSPS or wildfire exposure, joint PSPS and 10 μg/m 3 higher wildfire PM 2.5 was associated with higher odds of respiratory encounters (1.16 [95% CI: 1.10, 1.22]), with evidence of multiplicative interaction. Associations were null for cardiovascular and psychiatric encounters.
Limitations include exposure misclassification, because we assigned exposure at the residential zip code level, aggregating circuit-level data and not accounting for individual behavior or the potential for PSPS events to impact wildfire PM 2.5 exposure.
Conclusions
PSPS events may increase risk of respiratory events requiring acute care utilization, especially when they co-occur with wildfire PM 2.5 .