Haze is the phenomenon of reduced visibility caused by fine solid or liquid particles suspended in the atmosphere. These particles scatter and absorb light, making distant objects appear faded, blurred or discolored. Haze differs from fog because it is primarily particulate matter rather than water droplets and can persist in dry conditions.
Causes and characteristics
Common contributors to haze include dust from soil and deserts, smoke from wildfires or agricultural burning, industrial and vehicle emissions, sea salt and secondary particles formed by chemical reactions in the air. Meteorological conditions such as temperature inversions, low wind and dry air can concentrate particles near the ground. Optical effects include a whitening of distant views and a muted sun; scientific measurements use visibility range and particle size categories (for example, PM2.5 and PM10) to describe severity.
Impacts on health, transport and environment
- Health: fine particles can penetrate the lungs and aggravate respiratory and cardiovascular conditions.
- Transport: reduced visibility creates hazards for road, marine and air travel.
- Environment: sunlight attenuation can affect temperature, plant growth and visibility in parks and heritage areas.
Public health advisories and air quality indices help communities respond. Individuals often rely on indoor filtration, masks or limiting outdoor activity during heavy haze. Authorities may address sources by controlling emissions, dust suppression and land management.
Distinctions and notable points: haze is sometimes used interchangeably with smog, though smog historically referred to smoke-and-sulfur mixes or to photochemical ozone-rich mixtures in urban areas. Haze episodes can result from local pollution or from long-range transport of smoke or dust. For additional context on atmospheric pollution and mitigation, see air studies, quality guidance, and information about smoke.