Harm of indoor air pollutants
Formaldehyde is a colorless and strongly irritating gas, which has been identified as carcinogenic and teratogenic by the World Health Organization. Formaldehyde pollution can cause eye tears, corneal and conjunctival congestion and inflammation, skin allergy, nasopharyngeal discomfort, cough, acute and chronic bronchitis and other respiratory diseases, as well as nausea, vomiting and gastrointestinal dysfunction. Severe cases can also cause persistent headache, pneumonia, pulmonary edema, loss of appetite, and even death. Long-term exposure to low-dose formaldehyde can cause chronic respiratory diseases, eye diseases, irregular menstruation and disorder in women, pregnancy syndrome, neonatal malformation and mental depression. In addition, it can also promote the physical decline of newborns and cause heart disease in children. According to the investigation of American medical department, formaldehyde pollution is the main reason for the increase of asthma in children aged 3-5.
Harm of benzene to human body
Benzene is a colorless, transparent, aromatic and volatile toxic liquid, which is the product of coal tar distillation or petroleum cracking. Benzene vapor can be volatilized at room temperature, and the higher the temperature, the greater the volatilization. In professional activities, benzene mainly enters the human body through the respiratory tract in the form of steam. Inhalation of high-concentration benzene vapor for a short time and low-concentration benzene vapor for a long time will cause physical harm to workers. Inhalation in a large amount in a short period of time can cause acute mild poisoning, which is characterized by headache, dizziness, cough, chest tightness, excitement and stumbling gait. At this time, if you continue to inhale, it can develop into severe acute poisoning. The patient is confused, his blood pressure drops, his muscles tremble, his breathing is shallow, and his pulse is fast and weak. Timely rescue can restore health in hours or days, but severe cases can also die of respiratory center paralysis. Long-term low-concentration exposure can lead to chronic poisoning, and symptoms gradually appear, mainly including blood system and neurasthenia syndrome, manifested as leukopenia, thrombocytopenia and erythropenia, dizziness, headache, memory loss, insomnia and so on. In severe cases, aplastic anemia, even leukemia and death may occur.
Harm of radon to human body
Radon is the only colorless, odorless and odorless natural inert gas produced by radium decay in nature. Radon is a radioactive gas, which is ubiquitous in our living environment. Since indoor radon hazards were first discovered in the late 1960s, scientific research has found that the radiation damage caused by radon accounts for more than 55% of the total environmental radiation suffered by human body, which poses a great threat to human health, and its incubation period is mostly over 15 years. Radon has been listed as an important indoor carcinogen by the International Agency for Research on Cancer (IARC) and the most dangerous carcinogenic factor by the US Environmental Protection Agency, so we must attach great importance to the harm of indoor radon.
Sources of radon: indoor radon is about 60.4% from the foundation and surrounding soil of buildings, 65,438+09.5% from building materials and 65,438+07.8% from outdoor air.
(1) Radon released from foundation soil. High concentrations of radon can be found in soil and rocks containing uranium, radium and thorium deep in the stratum. These radon can pass through the stratum fault zone, enter the soil and atmosphere, and spread indoors along the cracks on the ground. Generally speaking, the indoor radon content of low-rise houses is high.
(2) Radon separated from building materials (including interior decoration materials) is one of the most important sources of indoor radon. Building materials usually contain radium in different degrees, especially building materials made of industrial waste residue or by-products contain more radium. Some radon produced by radium decay enters the room through diffusion. The radon exhalation ability of building materials is not only related to its radium content, but also related to the porosity, particle size, pore geometry, water content and pressure change of building materials.
(3) Radon brought into the room by outdoor air. The radiation dose of radon in the outdoor air is very low, but once it enters the room, it will accumulate in large quantities. Indoor radon also has obvious seasonal variation: through experiments, it is the highest in winter and the lowest in summer. It can be seen that indoor ventilation directly determines the harm of indoor radon to human body.
(4) Radon released by burning water and natural gas. Only when the radon content in water and natural gas is relatively high will it be harmful. Harm of radon and its daughters: The harm of radon to human beings was first discovered in Germany more than 100 years ago. At that time, the incidence of lung cancer among miners in the German sniper mining area was extremely high, so it was named "sniper disease". Forty-five years later, it was discovered that this may be because of the high radon concentration in the air of the mine. It was not until 1950s that radon was finally identified as one of the important causes of lung cancer. In this way, people have gradually realized the harm of radon and its short-lived daughters to health from the experience of increasing the incidence of lung cancer in miners who have been exposed to high levels of radon and its daughters for a long time.
The harm of radon to human body is mainly manifested in deterministic effect and stochastic effect, and the deterministic effect is manifested in the changes of blood cells in the body under high concentration radon exposure. Because radon has a high affinity for human fat, especially when combined with the nervous system, the random effect is mainly to induce tumors. Because radon is a radioactive gas, radon gas and its daughters enter the lungs with the airflow when breathing, and when radon daughters decay, they emit rays, bombarding lung cells like small bombs and damaging lung cells, thus causing the possibility of lung cancer. If the particles released by radon decay enter the human body through breathing, they will destroy the DNA of cells and tissues, thus inducing cancer. The American Surgical Association estimates that lung cancer caused by it accounts for about 15% of the incidence of lung cancer, second only to smoking. At the same time, radon has a high solubility in liquid and fat, and it will gather in organs with more fat and decay to produce radon daughters, which will do harm to human body. Under the influence of high concentration of radon, the total number of bleeding cells (red blood cells and white blood cells) increases, blood pressure decreases and blood vessels dilate. Alpha rays emitted by radon daughters are one of the main causes of human lung cancer and hematological diseases. External irradiation of alpha and beta rays will damage people's five senses, lead to diseases such as dry skin and alopecia, and even lead to skin cancer in severe cases. Medical research has confirmed that radon gas may also cause leukemia, infertility and fetal malformation.
Different organs of human body are exposed to different doses of radon daughters, of which the lung receives the largest dose. The dose distribution of radon daughters in lung is also uneven, and the dose of basal cell layer of trachea and bronchial epithelium is much higher than the average dose in lung area or whole lung. Because lung mass and respiratory rate change with age, for a given radon daughters concentration in the air, the effective dose equivalent may reach the maximum at about 6 years old, which is about 2.5 times higher than that at 30 years old. On average, the effective dose equivalent of children before 10 is about 2 times that of adults1.5. Therefore, the main harm of radon and its daughters to long-term contacts is the increase of lung cancer incidence, especially to children.
Scientists estimate that if you live in an indoor radon concentration of 200 Bq/ m3, it is equivalent to smoking 15 cigarettes per person every day. Scientific research shows that radon is the second leading cause of lung cancer besides smoking. The World Health Organization listed it as one of the main environmental carcinogens of 19, and the International Agency for Research on Cancer also considered radon as an important indoor carcinogen.
Radon concentration control measures
(1) Ventilate frequently, and keep the indoor and outdoor pressure difference to zero.
(2) Laying isolation layer can reduce the amount of radon entering the new house to some extent.
(3) Radon-proof coating
Covering the wall with decorative veneer can reduce radon exhalation, and coating some paint on the wall and ground can effectively inhibit radon exhalation. Brick coated with white ash can reduce the sedimentation rate by about 3 times, and white ash coating can reduce the sedimentation rate 1 times. If a layer of material with good sealing performance is coated on the inner surface of underground engineering, some radon can be prevented from escaping, thus reducing the radon escape rate. Generally, materials with better moisture resistance have better radon resistance. This is because moisture-proof materials generally have good sealing performance to prevent moisture emission and radon exhalation. There is a radon-proof and moisture-proof coating abroad called "RadonSeal". This kind of coating can penetrate to a certain depth when it is painted on concrete or brick, which can increase the density and strength of concrete and brick and achieve better radon prevention effect. A domestic university has developed an environmental protection radon-proof interior wall coating, which adopts the cross-linking polymerization technology of double-layer film materials to improve the compactness and durability of the coating, and prevent radon and moisture.
Harm of ammonia to human body
Chemical properties of ammonia: ammonia is a colorless gas with a strong pungent smell, which is lighter than air (specific gravity 0.5). Harm of ammonia to human body: ammonia is an alkaline substance, which can corrode and stimulate the skin tissue it contacts, absorb the moisture in the skin tissue, denature the tissue protein, saponify the tissue fat and destroy the cell membrane structure. When the concentration is too high, in addition to corrosion, it can also cause cardiac arrest and respiratory arrest through the reverse action of trigeminal nerve endings. Ammonia is usually inhaled into alveoli in the form of gas. After ammonia is inhaled into the lungs, it can easily enter the blood through alveoli, combine with hemoglobin, and destroy the oxygen transmission function. The solubility of ammonia is extremely high, so it mainly stimulates and corrodes the upper respiratory tract of animals or human bodies, and weakens the resistance of human bodies to diseases. A small amount of ammonia is neutralized by carbon dioxide, and the remaining small amount of ammonia is absorbed into the blood, which can be excreted with sweat, urine or respiratory tract. Some people will have symptoms such as skin pigmentation or finger ulcers when they are exposed to ammonia for a long time; After inhaling a large amount of ammonia in a short time, symptoms such as tears, sore throat, hoarseness, cough, chest tightness with bloodshot sputum, dyspnea, dizziness, headache, nausea, vomiting and fatigue may appear. In severe cases, pulmonary edema, adult respiratory distress syndrome and respiratory irritation may occur. Therefore, alkaline substances do deeper and more serious damage to tissues than acidic substances. In order to prove that the low concentration of ammonia in the air is also harmful to human health, experts have monitored the workers working in the indoor environment with the ammonia concentration of 3 ~ 13 mg/m3 for 8 hours, each group has 10 people, and compared with the healthy people who have not been exposed to ammonia. It was found that the contents of urea and ammonia in urine increased in the experimental group, while urea in blood increased significantly.
Source of ammonia in the air: (1) mainly comes from concrete admixture used in building construction, especially in winter construction, concrete antifreeze with urea and ammonia as main raw materials is added to concrete walls. These additives containing a large amount of ammonia are reduced to ammonia in the wall with the changes of environmental factors such as temperature and humidity, and are slowly released from the wall, resulting in a substantial increase in the concentration of ammonia in the indoor air. (2) Additives and brighteners in interior decoration materials Ammonia in indoor air can also come from additives and brighteners in decoration materials. However, the release period of this pollution is relatively fast, and it will not accumulate in the air for a long time, which is less harmful to human body.
The harm of TVOC to human body
Total Volatile Organic Compounds (TVOC): Volatile organic compounds are usually represented by VOC (acronym of three words), but sometimes TVOC is also used. TVOC is one of the three major organic pollutants (polycyclic aromatic hydrocarbons, volatile organic compounds and aldehydes) in the air. VOC refers to the organic matter whose saturated vapor pressure exceeds 133.32pa at room temperature. Its boiling point is between 50℃ and 250℃, and it can exist in the air as evaporation at room temperature. Its toxicity, irritation, carcinogenicity and special odor will affect the skin and mucosa and cause acute damage to the human body. The World Health Organization (WHO), National Academy of Sciences/National Research Council (NAS/NRC) and other institutions have always emphasized that TVOC is an important air pollutant. TVOC may be odorous and irritating, and some compounds are genotoxic. TVOC can cause the imbalance of immune level, affect the function of central nervous system, and have symptoms such as dizziness, headache, drowsiness, fatigue and chest tightness. It may also affect the digestive system, causing loss of appetite and nausea. Severe cases may damage the liver and hematopoietic system, causing allergic reactions.
TVOC is divided into eight categories: alkanes, aromatics, alkenes, halogenated hydrocarbons, esters, aldehydes, ketones and others. They all appear at the micro and micro levels, so they are easily overlooked. They mainly come from: organic solutions, such as paints, waterborne coatings, adhesives, cosmetics, detergents, caulking glue, etc.; Building materials: such as wood-based panels, foam insulation materials, plastic plates, etc. Interior decoration materials: decorations such as wallpaper; Fiber materials: such as carpets, tapestries, chemical fiber curtains; Incomplete combustion of domestic fuel and tobacco leaves, human excrement.