Particulate Matter, Fine (PM2.5)

Fine particulate matter is a complex mixture of very small
liquid droplets or solid particles in the air. Major sources are
cars, trucks, construction equipment, coal-fired power plants,
wood burning, vegetation and livestock. These particles can be
directly released when coal, gasoline, diesel fuels and wood are
burned. Many fine particles are also formed in the atmosphere
from chemical reactions of nitrogen oxides, sulfur oxides,
organic compounds and ammonia. Fine particulates are associated
with increased hospitalizations and deaths due to respiratory
and heart disease and can worsen the symptoms of asthma. People
with respiratory or heart disease, the elderly and children are
the groups most at risk. Fine particles are also major
contributors to reduced visibility (haze).