Denser forests due to suppression have increased forest fire severity in California, and therefore emissions from forest fires. These changes have made forest ecosystems in California more vulnerable to climate change, while at the same time exposing California populations distant from forests to health effects from fire emissions enhanced by the legacy of past land management. Despite direct connections to health, effects of wildfire emissions on public health are poorly quantified in California. Here, we seek to quantify a direct link between public health, ecological disturbance, climate change, and land management. We estimated wildfire PM2.5 emissions using the Fire Inventory from NCAR (FINN) model on a 1/16° latitude/longitude grid as a function of the area burned; fuel consumption under low, moderate, and high fire severity; and emission factors for coarse vegetation type. We used respiratory hospital admissions to quantify health effects and assessed the correlation with wildfire PM2.5 emissions during the period 1999-2013.
Results/Conclusions
PM2.5 emissions from each wildfire event in California during 1999-2013 were calculated. Emissions varied significantly and were dependent on fire size, fire severity, and vegetation characteristics. The distribution is highly positively skewed that most of the wildfires emitted a relatively small amount of emissions while the largest 10 wildfires contributed 27.63% of total PM2.5 emissions (1423Gg) from 1999 to 2013. Average emissions during drought periods 2001-2003, 2007-2009, 2012-2013 in California were significantly higher than non-drought years (p-value = 0.004). Forest is the major emission source. Preliminary results indicated a weak positive relationship (0.114) between wildfire PM2.5 emissions and total respiratory visits in the fall season in California. Next steps are to include better quantification the impact of wildfire PM2.5 emissions on respiratory visits at the zip code level and adjust for the potential confounding effects of temperature and seasonality.