Small message:
Asthma in children is 0.06-0.07mg/m3.
Up to 0. 1 mg/m3, there will be peculiar smell and discomfort.
Up to 0.5 mg/m3 will irritate eyes and cause tears.
Up to 0.6 mg/m3 throat discomfort or pain.
Up to 30 mg/m3, causing immediate death.
With the development of chemical industry and the modernization of living facilities, the output of formaldehyde and formaldehyde resin in China has increased year by year, and its application scope has become wider and wider. The formaldehyde emitted into the air by fuel combustion and building decoration materials is increasing year by year, especially in today's indoor decoration fever, indoor formaldehyde pollution has aroused great concern.
Formaldehyde is a highly irritating gas and a volatile organic compound. Its health effects are manifested as irritation to eyes and respiratory tract, resulting in abnormal lung, liver and immune functions. It has been reported abroad that formaldehyde with a concentration of 0. 1.2 mg/m3 makes children susceptible to asthma. 1995, formaldehyde was identified as a suspected carcinogen by the International Agency for Research on Cancer (IARC).
Physical and chemical characteristics of (1) formaldehyde, also known as ant aldehyde, is colorless and has a strong pungent smell. Its specific gravity to air is 1.06, which is slightly heavier than air and easily soluble in water, alcohol and ether. Its 30% ~ 40% aqueous solution is formalin solution. Formaldehyde is easy to polymerize into paraformaldehyde, easy to depolymerize when heated, and can slowly release formaldehyde at room temperature. The odor threshold of formaldehyde is 0.06 ~ 1.2 mg/m3, and the eye irritation threshold is 0.0 1 ~ 1.9 mg/m3.
(2) Source of Formaldehyde is an air pollutant with a wide range of sources, and formaldehyde in nature is an intermediate product in the methane cycle. Low background values are usually
① Formaldehyde in outdoor air Formaldehyde in outdoor air mainly comes from the combustion of oil, coal, natural gas and other fuels, the oxidative decomposition of lubricating oil, automobile emissions and atmospheric photochemical reactions. Burning 1000 gallon of oil can produce 0.272 ~ 0.908 kg of formaldehyde. Automobile exhaust contains about 70mg/kg of formaldehyde. Burning 1t coal can produce 2.3g of formaldehyde, and the flue gas from coal combustion contains 4 ~ 6mg/kg of formaldehyde. The concentration of formaldehyde in the air is high. The typical concentration of formaldehyde in Los Angeles 1962 is 0.02 ~ 0. 19 mg/kg. Formaldehyde in the atmosphere also comes from factories that produce formaldehyde, urea-formaldehyde resin, chemical fiber, dyes, rubber products, plastics, ink, paints and coatings.
Because of its strong chemical reaction and low price, formaldehyde was widely used in industrial production 100 years ago, mainly used to produce urea-formaldehyde resin, melamine-formaldehyde resin, phenolic resin, etc., which were all discharged into the atmosphere during production.
② Indoor formaldehyde sources Formaldehyde mainly comes from building materials, furniture, various adhesive coatings, synthetic fiber fabrics and different indoor sources.
A. wooden board. Formaldehyde is the preferred raw material for plywood, blockboard, medium density fiberboard and particleboard for interior decoration. Because of its strong adhesion, it has the function of insect prevention and corrosion protection, and its price is low.
Urea-formaldehyde resin is also used as thermal insulation material for buildings. The residual and unreacted formaldehyde in the board will be gradually released into the surrounding environment, and the longest release period can reach more than ten years, which is the main body of formaldehyde in indoor air. It is determined that the plywood with 65438±000 cm2 can release 3 ~ 65438 08 μ g of formaldehyde within 65438 0 h. The maximum formaldehyde content of the house built with urea-formaldehyde foam insulation material can reach 8.2mg/kg. The formaldehyde concentration of newly-built houses with more wood chips and fiberboards is 2 ~ 5 times higher than that of houses that have been used for 5 years. The formaldehyde concentration in the air of newly purchased furniture is also high, which can reach 0. 1mg/kg for a long time.
B. synthetic fabrics, such as carpets. Adhesives in carpets and interior decoration materials such as wall covering, wallpaper and foam will release formaldehyde.
The pollution of formaldehyde released by synthetic fiber fabrics to indoor environment can not be ignored. In order to improve the properties of synthetic fibers, resin finishing agent containing formaldehyde is usually used for resin finishing. Therefore, the finished fabric often contains a small amount of unreacted resin finishing agent. These resin-finished chemical fiber fabrics will release free formaldehyde during use and storage. It is estimated that 1kg synthetic fiber fabric can release 750mg of formaldehyde.
C. Incomplete combustion of fuel and tobacco leaves and distribution of books. Fuel combustion will produce a lot of formaldehyde. If the kitchen uses coal stoves and liquefied petroleum gas at the same time, the formaldehyde concentration is greater than 0.4mg/m3, and the peak pattern of daily variation of formaldehyde concentration in the kitchen is related to cooking time. In addition, cigarette smoke contains formaldehyde 14 ~ 24 mg/m3. People can inhale 8 1μg formaldehyde (about 40ml) at most every time they smoke. The indoor formaldehyde concentration is about 3 times higher when someone smokes than when no one smokes. It is determined that a new book with a thickness of 2cm can release 1μg formaldehyde in one hour. The formaldehyde concentration in libraries with many books and poor ventilation is obviously higher than that outside, and some of them are as high as 0.08mg/kg. It is found that carbonless copy paper will release a lot of formaldehyde.
D formaldehyde will be released when cosmetics, detergents, pesticides and preservatives are used.
(3) The harm of formaldehyde to human health
Formaldehyde is irritating to people's eyes, nose and respiratory tract. When the air contains 0.6mg/m3, it will cause irritation to eyes. People will cry if they stay in an air environment containing 10ppm formaldehyde for a few minutes. The main effects of low concentration formaldehyde on human body are skin allergy, cough, excessive phlegm, insomnia, nausea and headache. People who have just moved into a room with particleboard as the floor will have reactions of aversion to smell, headache, dizziness and cough. The formaldehyde concentration in such a room is sometimes higher than 0.5mg/m3. The influence of formaldehyde on the central nervous system is obvious. An epidemiological survey of families who use more urea-formaldehyde resin and family members who don't use synthetic fiberboard shows that people living in families with formaldehyde concentration of 0.0 1 ~ 3. 1 mg/m3 have more symptoms of headache, dizziness and insomnia than those who can't detect formaldehyde. Formaldehyde has a strong stimulating effect on human skin. When the air concentration is 0.5 ~ 10 mg/m3, it will cause redness and swelling. Low concentration of formaldehyde can inhibit sweat gland secretion and make skin dry.
② When the formaldehyde concentration is 0. 12 ~ 1.2 mg/m3, that is, (0. 1 ~ 1 ppm), it can cause abnormal liver function, abnormal lung function and abnormal immune function. When the concentration is 0.06 ~ 0.07 mg/m3 (0.05 ~ 0.06 ppm),
(3) Formaldehyde reacts with ions in the air to generate chloride and carcinogen-dichloromethyl ether, which has aroused people's vigilance.
④ Stimulation, sensitization and mutagenicity of formaldehyde. According to a large number of documents, the effects of formaldehyde on human health are mainly manifested in abnormal sense of smell, irritation, allergy, abnormal lung function and immune function, and there are great differences among individuals. In most reports, its concentration is above 0.12mg/m3 (0. 1ppm). It has been reported that children have asthma when its concentration is 0.06 ~ 0.07 mg/m3 (0.05 ~ 0.06 ppm). The harm of formaldehyde to health mainly includes the following aspects.
A. irritation: the main harm of formaldehyde is irritation to skin and mucosa. Formaldehyde is a toxic substance in protoplasm, which can combine with protein. Inhalation of high concentration will cause severe irritation and edema of respiratory tract, eye irritation and headache.
B sensitization: direct contact with formaldehyde can cause allergic dermatitis, pigmentation and necrosis, and inhalation of high concentration formaldehyde can induce bronchial asthma.
C. Mutagenesis: High concentration of formaldehyde is still a genotoxic substance. High concentration inhalation of experimental animals in the laboratory can cause snuff tumors. At present, it is generally believed that the concentration of formaldehyde in non-industrial indoor environment is not enough to cause tumors and cancers in human body.
(4) formaldehyde pollution control
(1) Indoor decoration adopts decoration materials with low formaldehyde content and no formaldehyde, and selects high-quality healthy and environmentally-friendly building materials that meet national standards.
(2) Paint should be applied to the kerf of wood-based panel to make it fully cured, which can form a stable protective layer and prevent the release of formaldehyde in the panel.
(3) It is not advisable to move in immediately after renovation. Windows should be opened for ventilation, so that the polluted air in the room can be emitted. Generally speaking, after several months of renovation, the indoor formaldehyde concentration can be reduced to below 0.08mg/m3, reaching the indoor qualified standard.
④ The release of formaldehyde in indoor decoration materials is related to indoor temperature, humidity, ventilation degree, service life of materials and load degree, that is, the surface area of materials that can release formaldehyde in 1m3 indoor space. High temperature, high humidity and negative pressure will accelerate the emission of formaldehyde, and strengthening ventilation frequency is beneficial to the emission and discharge of formaldehyde.
⑤ Indoor greening: Planting plants such as chlorophytum and aloe indoors will reduce the indoor harmful gas concentration.
(5) Limit value of indoor formaldehyde China's Hygienic Standard for Public Places stipulates that the maximum allowable concentration of formaldehyde in the air is 0. 12mg/m3. The hygienic standard of formaldehyde in indoor air is 0.08 mg/m3 (GB/T16127-1995).