Haze and smog are both forms of air pollution that reduce visibility, but they differ significantly in their composition and formation.
Haze
Haze is a suspension of very small, dry molecules in the air. Unlike fog and mist which contain water droplets, haze consists of dry particles. These particles, often invisible individually, scatter sunlight, causing a reduction in visibility and a hazy appearance. The sources of these particles can be natural (dust, pollen) or human-made (pollution from industrial emissions, vehicle exhaust). The EPA states that haze is caused when sunlight encounters these tiny pollution particles in the air, with some light absorbed and some scattered. [Source: US EPA]
Smog
Smog, on the other hand, is a type of air pollution that's a complex mixture of smoke, gases, and chemicals. It's typically more dense and visually impactful than haze, often appearing thick and dark or yellowish in color. Smog formation frequently involves a chemical reaction between sunlight and pollutants like volatile organic compounds (VOCs) and nitrogen oxides (NOx), creating ozone. This often happens during the daytime. [Source: Reddit r/InlandEmpire] A combination of man-made pollution and naturally occurring fog can also contribute to smog, as seen in the Po River Valley. [Source: NASA Earth Observatory]
Key Differences Summarized:
| Feature | Haze | Smog |
|---|---|---|
| Composition | Dry, small particles | Mixture of smoke, gases, and chemicals |
| Formation | Scattering of sunlight by particles | Chemical reactions involving sunlight |
| Appearance | Mild reduction in visibility, hazy | Dense, reduced visibility, dark/yellowish |
| Time of Day | Can occur anytime | Often more prevalent during the day |
Examples:
- Haze: Dust storms, pollen in the air, smoke from distant wildfires.
- Smog: Industrial emissions in a city, vehicle exhaust on a sunny day.
In short, while both reduce visibility, haze is primarily a scattering effect from dry particles, while smog is a chemically complex mixture of pollutants, often with a more pronounced visual impact and stronger association with daytime sunlight reactions.
