Haze is a combination of fog and haze. Fog is actually water droplets scattered in the air. Specifically, it is a colloidal dispersion system (friends who don't know what a dispersion system is have to review high school chemistry). Because it is a dispersed system, its diameter is very small, generally in the order of nanometers; Haze is a solid or liquid particle suspended in the air, which is of course different from dispersion system. It's much bigger. For example, the combination of fog and haze is like a car full of millet mixed with dozens of watermelons.
PM2.5 poses a greater threat to the human body, so where does PM2.5 come from? What's the ingredient? Compared with natural generation (wind-blown dust, volcanic ash, forest fire, floating sea salt, pollen, fungal spores, bacteria), the main source of PM2.5 is man-made emission: direct emission mainly comes from the combustion process, such as the combustion of fossil fuels (coal, gasoline, diesel oil), biomass (straw, firewood), garbage incineration, etc. The main gaseous pollutants converted into PM2.5 in the air are sulfur dioxide, nitrogen oxides, ammonia and volatile organic compounds. Other anthropogenic sources include road dust, construction dust, industrial dust and kitchen smoke.
Is smog harmful to human health? The answer is yes. Specifically, smog is a combination of solid particles, sulfuric acid, nitric acid and other substances. There are more than 20 kinds of toxic substances in solid particles, especially the well-known inhalation of PM2.5, which can easily cause upper respiratory tract infection, sinusitis and even cerebrovascular diseases.
Can wearing a mask prevent smog from harming the human body? Depends on what kind of mask it is. Ordinary masks can keep warm at most. What is really useful is a medical mask, which is divided into three layers. The middle layer plays a major role in filtration. Generally, it is superfine polypropylene, which can reduce the call of PM2.5. Of course, this mask also has shortcomings. It will be uncomfortable to wear, with high use conditions and no pollution.
In fact, as long as you stay in a smoggy environment for a long time without a fine, no mask can be 100% smog-proof. So what we have to do is to minimize the time to go out in foggy days. When we are outdoors, we must wear masks as much as possible, and then wait quietly for this time to pass. Cold air going south will bring us back to the clear sky!