Background: The largest gas leak in United States history occurred October 2015 through February 2016 near Porter Ranch (PR), California, and prompted the temporary relocation of nearby residents because of health concerns related to natural gas exposure.
Methods: A retrospective cohort study was conducted using US Department of Veterans Affairs (VA) administrative and clinical data. On the basis of zip codes, we created two groups: PR (1920 patients) and San Fernando Valley (SFV) (15 260 patients) and examined the proportion of outpatient visits to VA providers with respiratory-related diagnoses between October 2014 and September 2017.
Results: We observed an increase in the proportion of visits in the PR group during the leak (7.0% vs 6.1%, P<0.005) and immediately after the leak (7.7% vs 5.3%, P<0.0001). For both groups, we observed a decrease in respiratory diagnoses one year after the leak (7.0% to 5.9%, P<0.05 PR; 6.1% to 5.7%, P<0.01 SFV).
Conclusion: Exposure to natural gas likely led to the observed increase in respiratory-related diagnoses during and after the PR gas leak. Early relocation following natural gas leaks may mitigate respiratory exacerbations. (Disaster Med Public Health Preparedness. 2019;13:419-423).