Views from Cadillac Mountain are sometimes obscured by air pollution that also threatens human health, Acadia’s water quality, and vegetation. A large percentage of this pollution comes from out of state as converging air currents from the South and Midwest carry chemicals and small particles to the Maine coastline. Most ground-level ozone and particle pollution comes from the burning of fossil fuels by industry, power plants, and motor vehicles. Ozone levels are usually higher in the summer, when increased sunlight drives the chemical reaction that produces ozone and can cause harmful spikes, while particle pollution can occur year-round. Park resource specialists monitor Acadia’s air for pollutants and their effects on plants, water, wildlife, and humans. Prevailing southwesterly winds carry pollutants there from industrialized areas in the South and Midwest, and actions at home can affect Acadia’s air quality.