Haze and Health
1. What do we mean by fog and haze?
Haze is a mixture of fog and haze, both of which lead to reduced visibility and have a serious impact on people’s daily lives. With the deterioration of air quality, the phenomenon of hazy weather has increased and the harm has worsened. In recent years, many regions in China have incorporated the hazy weather phenomenon into fog as a catastrophic weather warning forecast, collectively referred to as “hazy weather”. However, fog is an aerosol system composed of a large number of tiny water droplets or ice crystals suspended in the air near the ground. The presence of fog reduces air transparency and worsens visibility. If the horizontal visibility of the target is reduced to within 1000 meters, the weather phenomenon of water vapor condensation suspended in the air near the ground is called fog, while the horizontal visibility of the target at 1000-10000 meters is called light fog or haze.
And haze, also known as haze, is a hazardous weather phenomenon produced by the combination of meteorological conditions and pollution factors with fine particulate matter (mainly PM10 and PM2.5, including particles of dust, sulfuric acid, nitric acid, organic hydrocarbons in the air) as a carrier, clouding the atmosphere, blurring the view and causing visibility to deteriorate. If the horizontal visibility is less than 10,000 meters, the visual range obstruction caused by this aerosol system of non-aqueous constituents is called haze. Anthropogenic sources are the main source of atmospheric particulate matter.
2.What is the difference between fog and haze?
Fog is a natural weather phenomenon, a product of water vapor condensation in the near-surface layer of the air, and although dust is used as a condensation nucleus, it is generally non-toxic and harmless; the core material of haze is smoke and dust suspended in the air, which can directly enter and adhere to the human lower respiratory tract and lung lobes, and is harmful to human health.
The difference between the two is shown by
Relative humidity of air: Haze occurs when the relative humidity is not large, less than 70%, while the relative humidity in the fog is saturated (such as the presence of a large number of condensation nodules, the relative humidity does not necessarily reach 100% may appear saturated). General relative humidity is less than 80% when the atmospheric haze field of view blurred visibility deterioration is caused by haze, relative humidity is greater than 90% when the atmospheric haze field of view blurred visibility deterioration is caused by fog, relative humidity between 80-90% when the atmospheric haze field of view blurred visibility deterioration is caused by a mixture of haze and fog together, but its main component is haze.
Thickness: Haze is relatively thick, up to about 1-3 km, with no obvious boundary between it and the clear sky area; fog is relatively small, from about a few tens of meters to about one to two hundred meters, with an obvious boundary between it and the clear sky area. Concentration distribution and scale: fog droplet concentration distribution is not uniform, and the scale of fog droplets is relatively large, from a few microns to 100 microns, the average diameter is about 10-20 microns, the naked eye can see the air floating fog droplets; haze particles are more uniformly distributed, and the scale of haze particles is relatively small, from 0.001 microns to 10 microns, the average diameter is about 1-2 microns, the naked eye can not see particles floating in the air.
Color: Because the light scattered by fog composed of liquid water or ice crystals has little relationship with wavelength, thus the fog looks milky white or greenish white; because the haze composed of dust, sulfuric acid, nitric acid and other particles, the light scattered by longer wavelengths is more, thus the haze looks yellow or orange-gray.
Inter-month distribution: The monthly distribution of fog days is uneven, mainly concentrated in October-December, while the monthly distribution of haze days is uniform, with small differences in haze days among months (Beijing).
3.What are the conditions for the formation of hazy weather?
Haze is the result of the combined effect of air pollution and meteorological factors. When hazy weather occurs, atmospheric visibility decreases, and atmospheric particulate matter, especially fine particulate matter (PM2.5), is the main factor leading to reduced visibility. The formation of hazy weather is mainly due to man-made environmental pollution, coupled with natural conditions such as low temperatures and low winds that result in pollutants that are not easily diffused. As temperature determines the level of relative humidity, the lower the temperature, the less water vapor the air can hold, and the higher the humidity, the easier it is to form fog. Fog itself is not pollution, but the atmospheric environment that produces fog is in a relatively stable state, the pollutants in the air is not easy to diffuse outward, resulting in the agglomeration effect, will make pollution more and more heavy. Similarly, urban pollutants in the low pressure, wind conditions, and the combination of water vapor in the lower air, will also increase the degree of haze. And the greater the wind speed the better the visibility, wind speed has an important role in the haze process visibility turnaround.
4.What are the main components of haze?
The composition of haze is complex, and most of the harmful elements and compounds are enriched in fine particulate matter. It has been found that 60-90% of harmful substances exist in particulate matter below 10um. The main components that have been detected are sulfates, nitrates, ammonium salts, and carbon-containing particles (including elemental carbon and organic carbon. Elemental carbon is mainly generated from high temperature combustion processes, and organic carbon is mainly from relatively low temperature combustion processes), heavy metals, and crustal materials. Secondary aerosol pollution, of which sulfate and nitrate are the main components, is also very likely to be formed under haze weather. The sulfur dioxide adsorbed on the particles is catalyzed and oxidized to sulfur trioxide, which forms a very fine sulfuric acid mist with water vapor.
5.Definition of PM2.5
PM, is the English particulate
PM consists of primary particles emitted directly into the air and secondary particles generated by the chemical transformation of gaseous pollutants in the air. Natural sources of primary particles generate about 4.41×10^6 tons per day
tons per day and about 0.3×10^6 tons per day from anthropogenic sources. The amount of secondary particles generated from natural sources is about .6×10^6 tons per day and about 0.37×10^6 tons per day from anthropogenic sources.
Total suspended particulate matter (P M100), respirable particulate matter (P M10) and lung-accessible particulate matter (P
M2.5) are three concepts frequently used in ambient air quality monitoring. According to the definition in the Ambient Air Quality Standards, PM2.5 refers to particulate matter in ambient air with a diameter less than or equal to 2.5 μm, also known as fine particulate matter. Scientists use PM2.5 to indicate the amount of such particles per cubic meter of air. The higher this value is, the more serious the air pollution is.
6.What are the main sources of PM2.5?
The main sources of atmospheric PM2.5 are thermal power generation, industrial production, automobile exhaust, biomass combustion, secondary generation, road dust and other processes. For particulate matter with particle size <2.5um, the primary particles, dusty particles are mainly from dust generated from roads, construction and agriculture; carbon black particles are mainly from diesel engine cars, boilers, waste incineration, open-air barbecue, fire straw and residents burning firewood, etc. Secondary particles ammonium sulfate and ammonium nitrate precursors SO2 mainly from coal-fired boilers and oil-fired boilers, NOx mainly from boilers and motor vehicles, etc..
Indoor PM2.5 its main sources generally include: outdoor pollution sources, indoor pollution sources and particle re-suspension caused by indoor activities. Among them, particulate matter entering indoors from outdoors is an important source of indoor PM2.5. Smoking and cooking are the main sources of indoor PM2.5 from indoor sources. Cigarette smoke particles are also mostly 0.1 to 1.0 um in diameter, and smoking indoors produces particulate matter with serious hazards due to incomplete combustion of cigarettes. The use of better quality cigarettes is also just a smoker’s self-assurance, and may even cause more harm because of the lower odor. The same applies to gold paper burning, burning incense and burning mosquito incense. In addition, building decoration materials, furniture, paints, coatings, etc. release and volatile formaldehyde, benzene and other harmful substances attached to PM2.5 particles, will increase the harm to humans. Indoor activities, cleaning and other secondary dust are also sources of indoor PM2.5.
The quality concentration of PM2.5 itself in the air is closely related to the meteorological conditions, in addition to being influenced by the source emissions and the distance between the receptor point and the pollution source. Thus, the mass concentration of PM2.5 in the air at the same time in different areas and at different times in the same region may vary greatly. Precipitation can reduce the concentration of airborne PM and keep the concentration of airborne PM at a low level for a period of time after precipitation. Wind can promote the outward diffusion of pollutants in the air and make visibility better.
7.What are the main hazards of hazy weather to human health?
Airborne particulate matter is relevant to human health in a clear sense. The particle size of particulate matter determines where it eventually enters the respiratory tract and how much it is deposited. Particles larger than 10um are eliminated by the nose and respiratory mucus, those below 10um can enter the nasal cavity, those below 7um can enter the throat, and those smaller than 2.5um (i.e. PM2.5) can reach deep into the alveoli and be deposited, entering the blood circulation and causing diseases related to cardiopulmonary dysfunction. At the same time, the smaller the particle size, the higher the stability in the atmosphere, the slower the settling speed, the longer the stay in the atmosphere, and the greater the chance of being inhaled into the human body (generally 10μm particles take 9h to settle to the ground, while 1μm particles take 9-98d, 0.4μm takes 120-140d, and <0.1μm takes 5-10 years). During hazy weather, most of the health effects are thought to be caused by the small particle size fraction PM2.5
PM2.5 is more closely related to human respiratory diseases, and the smaller the diameter the deeper the location into the respiratory system. PM2.5 is also very easy to adsorb harmful substances such as polycyclic aromatic hydrocarbons, heavy metals, bacteria and viruses, which seriously endanger human health after entering the human body. increased PM2.5 concentration is significantly associated with an increase in the number of emergency and outpatient patients in hospitals.
Particulate matter itself contains many harmful substances and is a carrier of pollutants, so the harm to human body is multifaceted. Many studies have now confirmed that particulate matter can cause damage to the respiratory and cardiovascular systems leading to asthma, lung cancer, cardiovascular disease, birth defects and premature death. For healthy people, particulate matter is not a direct cause of death, but it can cause death in patients with cardiovascular disease, respiratory disease and other diseases of sensitive body, and people who are in the environment of high concentration of fine particulate matter for a long time have higher chance of heart and lung disease and lung cancer mortality. Data show that when PM10 daily average increase of 10ug/m3, the total mortality rate of the population will increase by 1% to 2%, of which the mortality rate of respiratory diseases will increase by 3% to 6%, the mortality rate of lung cancer will increase by 8%, and the mortality rate of cardiovascular diseases can increase by 1% to 2%. It is also found that the effect of pneumonia, heart disease and some other diseases increased mortality, with the population exposed to fine particles in the environment for a longer period of time and increased. 2010 Beijing, Shanghai due to PM2.5 pollution deaths have been close to the number of traffic accident deaths in the same period of three times.
8.What are the effects of hazy weather on respiratory diseases?
Studies have shown that an increase in PM2.5 concentration is significantly associated with an increase in the number of patients with respiratory diseases. Atmospheric particles entering the respiratory tract can stimulate and corrode the alveolar wall, causing damage to the respiratory defense function and impairing lung function,
The incidence of respiratory symptoms such as coughing, coughing and wheezing increases. It has been found that during the haze period, people have increased symptoms of upper respiratory tract infections, asthma, conjunctivitis, bronchitis, eye and throat irritation, cough, dyspnea, nasal congestion and runny nose, skin rash, and cardiovascular system disorders, with children and the elderly being more likely to suffer from these diseases.
There are a large number of harmful substances, bacteria, viruses, pollen, and mold spores in atmospheric particulate matter. Three types of respiratory diseases caused by atmospheric particulate matter deserve attention during hazy weather: infectious diseases: including influenza, tuberculosis, and pneumonia; allergies: including asthma and alveolitis caused by natural allergens; and malignant diseases such as lung cancer. Short-term exposure to haze can induce lung diseases such as asthma, acute bronchitis, and respiratory infections, while long-term exposure can lead to decreased lung function, chronic bronchitis, and chronic obstructive pulmonary disease.
Particulate matter has adverse effects on the onset and exacerbation of asthma symptoms in both children and adults. In areas of high PM2.5 pollution,
the prevalence of exercise-induced bronchitis, hereditary atopic dermatitis, asthma, and hereditary allergic asthma were significantly higher than in the low concentration zone; people living near high traffic flow,
The risk of wheezing and allergic rhinitis was also elevated in people living near high traffic volumes; increased levels of particulate matter were associated with increased symptoms, medication use and hospital admissions in asthma patients. The mechanism of particulate matter-induced asthma and allergic diseases is related to the immune adjuvant effect of particulate matter.
Prolonged exposure to haze and the entry of particulate matter into lung tissue causes local oxidative stress and inflammatory responses, and oxidative stress can damage biofilm lipids, proteins and DNA,
Oxidative stress can damage biofilm lipids, proteins and DNA, and together with inflammatory factors lead to respiratory tract damage, changes in the ultrastructure of both the respiratory and nasal mucosa, damage to a variety of respiratory cells and an increase in neutrophils. Exposure to higher concentrations of particulate matter during childhood,
Exposure to higher concentrations of particulate matter in childhood may lead to earlier onset of COPD symptoms, and exposure in adulthood may promote the onset and progression of COPD, leading to increased morbidity and mortality.
One of the main components of haze is carbon, especially organic carbon, which seriously affects human health. PAHs are carcinogenic, mutagenic and teratogenic. Its representative benzo(a)pyrene (BaP) is the most carcinogenic substance, which can induce skin cancer, lung cancer and stomach cancer. In addition, PAHs in the air can react with O3, NOx, HNO3, etc. and transform into compounds with stronger carcinogenic or mutagenic effects, thus posing a threat to human health. In addition, sulfuric acid mist from secondary aerosol pollution can invade the respiratory tract more deeply and has a stronger toxic effect on the alveoli. When sulfur dioxide and particulate matter are absorbed into the body at the same time, a synergistic effect occurs, and the harm to humans is more serious. Epidemiological surveys show that there is a correlation between lung cancer mortality and atmospheric TSP and S02 pollution in China. Heavy metals such as cadmium, nickel, manganese, vanadium, bromine, zinc and other harmful components, which are mainly adsorbed on particles less than 2.5um in diameter, also contribute to the occurrence of lung cancer.
10. The effect of hazy weather on the health of other systems.
PM2.5 pollution causes cardiovascular events with increased cardiovascular morbidity and mortality, mainly involving altered heart rate variability, myocardial ischemia, myocardial infarction, arrhythmias, atherosclerosis, etc. ,
These health risks are more pronounced in susceptible populations,
These health risks are more pronounced in susceptible groups, such as the elderly and patients with cardiovascular diseases. In addition, it can also cause neurological damage, reduce immune function and affect the growth and development of children. Hazy weather can also affect people’s psychological health, making people depressed, pessimistic and other adverse emotions.
11, haze weather coping strategies.
Maintain good health, have a balanced diet, eat lightly, drink more water, pay attention to increase and decrease clothing, exercise in moderation, get enough rest, and avoid excessive fatigue.
Reduce going out, shorten the time of outdoor activities, the old and frail and children, especially residents with cardiovascular and cerebrovascular diseases should pay more attention to protection, pay attention to increase and decrease clothing when going out, pay attention to keep warm, and try to wear a mask.
The elderly should not take morning exercise outdoors in hazy weather, it is recommended to do some simple activities indoors and reduce the amount of activity. Pay attention to maintaining indoor air hygiene. It is not conducive to opening windows and ventilation during extreme weather, so activities that aggravate indoor air deterioration such as indoor smoking, excessive cooking of fried food and barbecue should be prohibited and reduced during this period. During the high season of influenza and other respiratory infectious diseases, it is recommended that the elderly and children go to less crowded and confined places with poor air circulation, stay away from patients with respiratory symptoms, and wear masks when visiting hospitals.
12.Can air purifiers block PM2.5?
pm10, pm2.5 belong to particulate matter, and air purifiers can block our naked eye visible ‘dust’ for particulate matter is basically the same as ineffective, there is no brand has been functional certification, there is no unified assessment standards for pm2.5, the actual effect of removing PM2.5 with air purifiers is difficult to guarantee.
13.Teach you to read the air quality standard report.
EPA’s public data provide data types including AQI air quality index, PM2.5 monitoring values, PM10 monitoring values, CO monitoring values, NO2 monitoring values, ozone 1 hour average monitoring values, ozone 8 hour average monitoring values, SO2 monitoring values for cities and indoor monitoring points.