UC Davis epidemiologist Irva Hertz-Picciotto has discovered a strong link between exposure to components of air pollution and acute bronchitis diagnoses in preschool-aged children. Those components – polycyclic aromatic hydrocarbons, or PAHs – contribute to air pollution from a variety of sources, including coal burning, vehicle exhaust, wood-burning stoves, tobacco smoke and grilling food. The PAH levels identified in the Czech Early Childhood Health Study, which involved 1,133 children from birth to 4.5 years of age, are comparable to those found in Western Europe and the United States, including some rural areas of California. The study was published in Environmental Health Perspectives.