Haze means gray haze (smog) The dust in the air, sulfuric acid, nitric acid, etc. caused by the visual range of obstacles called haze. The difference between haze and fog is that haze occurs when the relative humidity is not large, while the relative humidity in the fog is saturated (such as the presence of a large number of condensation nuclei, the relative humidity does not have to be saturated up to 100% may occur).

Three items, sulfur dioxide, nitrogen oxides and respirable particulate matter, are the main components of haze; the first two are gaseous pollutants, and it is the last item, particulate matter, that is responsible for adding to the pollution of the hazy weather, which combines with the fog to make the sky instantly cloudy and gray. Particulate matter is abbreviated as PM, and Beijing monitors fine particulate matter (PM2.5), which are pollutant particles with a diameter less than or equal to 2.5 microns. Such particles are both a pollutant in their own right and a carrier of heavy metals, polycyclic aromatic hydrocarbons and other toxic substances.

Eating greens can prevent haze poisoning is pure speculation, and humans eat greens every day. The main prevention is to minimize outdoor exercise, the use of masks or air purifiers and other products.