What does pm2.5-44 mean in weather forecast?

PM2.5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, also known as particles that can enter the lungs. Its diameter is less than 1/20 of the thickness of human hair. Although PM2.5 is only a small part of the composition of the earth's atmosphere, it has an important impact on air quality and visibility. Compared with atmospheric coarse particles, PM2.5 has a small particle size, is rich in a large number of toxic and harmful substances, stays in the atmosphere for a long time and has a long transportation distance, so it has a great impact on human health and atmospheric environmental quality.

According to the new air quality standard of PM2.5 detection network, the standard value distribution of 24-hour average is as follows:

Average standard value of air quality grade PM2.5 hours

Excellent 0~50

Beam 50~ 100

Light pollution 100~ 150

Moderate pollution 150~200

Heavy pollution 200~300

Serious pollution is greater than 300 and above.

Hazard introduction

health hazard

In 1970s, people began to notice the connection between particulate pollution and health problems. In the United States, the number of deaths caused by particulate pollution is about 22,000-52,000 every year, and in Europe in 2000, the number was as high as 200,000.

Now many studies have confirmed that particulate matter can cause harm to respiratory system and cardiovascular system, leading to asthma, lung cancer, cardiovascular disease, birth defects and premature death.

PM2.5 was identified as carcinogen folding.

At the meeting in Lyon, the International Agency for Research on Cancer (IARC) has identified air pollution as a carcinogen, which has also been recognized by experts. In fact, in detail, it is atmospheric particulate matter, the so-called PM2.5, which is a confirmed human carcinogen. It is mentioned like this. It should be said that this is recognized by experts, and there are indeed many detailed scientific data to confirm it. It's okay to think like this, no problem. [4]

respiratory system

The size of particles determines their final position in the respiratory tract. Larger particles are often filtered by cilia and mucus and cannot pass through the nose and throat. But particles smaller than 10 micron can be inhaled, and PM 10 can penetrate these barriers to reach bronchi and alveoli. However, particles smaller than 2.5 microns and fine particles PM2.5 are more likely to adsorb toxic substances than PM 10. Due to its smaller size and stronger penetration, PM2.5 may reach the bronchiole wall and interfere with the gas exchange in the lungs. Smaller particles with a diameter less than or equal to 100 nm will spread through the lungs and affect other organs.

Cardiovascular problems

A study published in the Journal of the American Medical Association shows that PM2.5 can lead to the deposition of arterial plaque, vascular inflammation and atherosclerosis, and eventually lead to heart disease or other cardiovascular problems. This study, which started at 1982, confirmed that when the concentration of PM2.5 in the air is higher than 10 μ g/m3 for a long time, the risk of death will increase. When the concentration increased 10 μg/m3, the total risk of death increased by 4%, the risk of death caused by heart and lung diseases increased by 6%, and the risk of death caused by lung cancer increased by 8%. In addition, PM2.5 is easy to adsorb organic pollutants and heavy metals such as polycyclic aromatic hydrocarbons, which significantly increases the probability of carcinogenesis, teratogenesis and mutation.

The harm caused by the minimum particle size less than or equal to 100 nm is more serious. There is evidence that these particles can cross the cell membrane and reach other organs including the brain. Studies have shown that these particles may cause brain damage, including Alzheimer's disease. It is worth noting that the diameter of particulate matter produced by diesel engines is usually around 100 nm.

Thanks for adoption