|
 |
|
|
|
|
|
新《生活饮用水卫生标准》GB5749- 项目解读（5）
二氯甲烷
分子式： CH2CL2
技术指标： 甲醇氢氯化再热氯化法产品采用，具体技术指标如下： 项 目 优等品 一等品 合格品 色度（Pt-Co）, 号 ≤ 10 10 10 酸度（以HCL计）， ％，≤ 0.0004 0.0008 0.0010 水份， ％，≤ 0.040 0.050 0.060 纯度， ％，≤ 99.5 99.0 98.0 蒸发残渣， ％，≤ 0.0005 0.0010 0.0030
【性能简述】
二氯甲烷是无色透明易挥发的液体，有类似醚的气味和甜味，相对密度1.326，熔点-96.7℃，沸点40.4℃。二氯甲烷与高浓度氧混合后会形成爆炸性混合物，但不易燃，是常用工业溶剂，中毒性小，不燃性的低沸点溶剂之一，对很多树脂，石蜡和脂肪都具有优良的溶解能力。微溶于水，易溶于其他氯代溶剂，乙醚和乙醇。二氯甲烷在一定温度下会与水发生水解反应。商品二氯甲烷常含有稳定剂，以防止分解。
【产品用途】
二氯甲烷具有溶解能力强和毒性低的优点，大量用于制造安全电影胶片，聚碳酸酯，其余用作涂料溶剂，金属脱脂剂，气烟雾喷射剂，聚氨酯发泡剂，脱模剂，脱漆剂。用于医药，有机合成，树脂等,还用于抵压冷冻机及空调装置的制冷.
。
【毒性和防护】
毒性很小,且中毒后苏醒较快，故可用作麻醉剂。对皮肤及粘膜有刺激性。空气中最高容许浓度500ppm。操作时应戴防毒面具，发现中毒后立即脱离现场 ，对症治疗。
【包装及运输】
包装贮存运输： 二氯甲烷用镀锌铁桶，黑铁桶或贮槽（槽车）密闭包装，填装系数不大于0.8。应存放在阴凉，干燥，通风处，并符合中华人民共和国铁路，公路对危险货物贮存和运输的有关规定。在包装，贮存，运输时，应注意检查包装容器的盖子是否紧密，不得渗透
| Synonyms | Methylene chloride |
|---|---|
| Dichloromethane | |
| Methane, dichloro- | |
| Analytical Methods | EPA Method 502.2
EPA Method 524.1 EPA Method 524.2 EPA Method 601 EPA Method 624 EPA Method 8010B EPA Method 8021A EPA Method 8240B EPA Method 8260A |
| Use | SOLVENT FOR CELLULOSE ACETATE; MEDICATION: ANESTHETIC (INHALATION) PAINT REMOVERS; VAPOR DEGREASING SOLVENT FOR METALS & PLASTICS SOLVENT & CLEANING AGENT IN THE CHEM PROCESSING INDUST BLOWING & CLEANING AGENT IN URETHANE FOAM INDUST IN CHEMICAL PROCESSING & AS CARRIER SOLVENT INSECTICIDES & HERBICIDES; AS A POST-HARVEST FUMIGANT FOR STRAWBERRIES, AS GRAIN FUMIGANT, & IN COMBINATION WITH ETHYLENE FOR DEGREENING CITRUS FRUITS SOLVENT FOR PLASTIC FILM, ADHESIVES, PROTECTIVE COATINGS; CLEANING SOLVENT FOR CIRCUIT BOARDS & STRIPPER SOLVENT FOR PHOTORESISTS IN PHARMACEUTICAL INDUSTRY AS A PROCESS SOLVENT IN PRODN OF STEROIDS, ANTIBIOTICS & VITAMINS & SOLVENT FOR TABLET COATINGS DECAFFEINATING COFFEE; EXTRACTION OF HEAT-SENSITIVE SUBSTANCES SUCH AS COCOA, EDIBLE FATS, SPICES & BEER HOPS REFRIGERANT; IN OIL DEWAXING; AS DYE & PERFUME INTERMEDIATE; AS CARRIER SOLVENT IN TEXTILE INDUSTRY COMPONENT OF FIRE EXTINGUISHING CMPD CHEM INT FOR BROMOCHLOROMETHANE & OTHER CHEMICALS In furniture processing In pour molding of dental material, the 50:50 mixture of dichloromethane and methylmethacrylate cold curing monomer is used to treat the acrylic teeth to improve the bonding Ingredient in nonflammable removers, strippers, & cements; used in aerosol formulations; in solid phase peptide synthesis; solvent for resins Low temp heat transfer medium |
| Consumption Patterns | Paint removers, 30%; metal cleaning/degreasing, 22%; miscellaneous solvent uses and other applications, 21%; aerosols, 17%; foam blowing agent, 5%; pharmaceutical solvent, 5% (1978). From table PAINT REMOVER, 30%; AEROSOLS, 20%; VAPOR DEGREASING, 11%; CHEM PROCESS INDUST, 11%; BLOWING AGENT, 6%; FILM PROCESSING, 6%; PLASTICS PROCESSING, 6%; PHARMACEUTICALS, 6%; OTHER, 4% (1981) Demand: 1982: 530 million lb; 1983: 530 million lb; 1987: 621 million lb. Aerosols, 30%; paint remover, 30%; foam blowing, 15%; fiber & plastic solvent, 5%; metal cleaning, 5%; miscellaneous, 15% (1985) CHEMICAL PROFILE: Methylene chloride. Paint stripper, 28%; aerosols, 18%; exports, 15%; chemical processing, 11%; urethane foam blowing agent, 9%; metal degreasing, 8%; electronics, 7%; other, 4%. CHEMICAL PROFILE: Methylene chloride. Demand: 1988: 500 million lb; 1989: 475 million lb; 1993 projected/: 410 million lb. (Includes exports, but not imports, which totaled 27 million lb last year). |
| Apparent Color | COLORLESS LIQ |
| Odor | Sweet, pleasant odor, like chloroform |
| Boiling Point | 39.75 DEG C @ 760 MM HG |
| Odor Threshold Concentration | 205-307 ppm 2.14x10 2 ppm (odor recognition in air; chemically pure sample) Odor thresholds: low= 540 mg/cu m; high= 2160 mg/cu m. Odor index: 2100 @ 20 deg C |
| Sensitivity Data | Irritation of eyes and respiratory tract. |
| Environmental Impact | Large quanitities of dichloromethane are used each year, primarily in aerosols, paint removers and chemial processing. The major route of human exposure is from air, which can be high near sources of emission, and contaminated drinking water. Most of the dichloromethane will be released to the atmosphere where it will degrade by reaction with photochemically produced hydroxyl radicals with a half-life of a few months. It will be subject to direct photolysis. Releases to water will primarily be removed by evaporation. Biodegradation is possible in natural waters but will probably be very slow compared with evaporation. It will not be expected to significantly adsorb to sediment or to bioconcentration in aquatic organisms. Releases to soil will evaporate rapidly from near-surface soil and partially leach into groundwater where its fate is unknown. Dichloromethane is not expected to bioconcentrate in the food chain, |
| Environmental Fate | TERRESTRIAL FATE: When spilled on land, dichloromethane is expected to evaporate from near surface soil into the atmosphere because of its high vapor pressure. Although little work has been done on its adsorptivity, it is probable that it will leach through subsoil into groundwater. Degradation in groundwater is unknown. Hydrolysis in soil or groundwater is not an important process under normal environmental conditions . AQUATIC FATE: Dichloromethane will be primarily lost by evaporation to the atmosphere which should take several hours depending on wind and mixing conditions. When released into a river, dichloromethane levels were non-detectable 3-15 miles from the source(1-2). Biodegradation is possible in natural waters but will probably be very slow compared with evaporation . Little is known about adsorption or bioconcentration in aquatic organisms to sediment but these are not likely to be significant processes. Hydrolysis is not an important process under normal enivronmental conditions . ATMOSPHERIC FATE: Dichloromethane released into the atmosphere will degrade by reaction with hydroxyl radicals with a half life of several months(1-3). It will not be subject to direct photolysis . A small fraction of the chemical will diffuse to the stratosphere where it will rapidly degrade by photolysis and reaction with chlorine radicals(1,5). A moderately soluble chemical such as dichloromethane will be expected to partially return to earth in rain. |
| Drinking Water Impact | DRINKING WATER: 30 Canadian Water Treatment Facilities - 50% positive - 10 ppb, avg, 50 ppb max (summer), 30% pos, 3 ppb avg, 50 ppb max (winter) ; 10 State survey drinking water from groundwater sources - 2% pos, 3600 ppb max, max surface water conc 13 ppb ; EPA Region V Survey (83 sites in 5 states: MN, WI, IL, IN, OH) - 8% pos, 1-7 ppb , National Organics Monitoring Survey (1976) - 15 of 109 samples positive, 6.1 ppb, mean of positive samples . EFFL: Weser R, Germany - 72-179 ppb . Industries in which wastewater exceeded an average of 1000 ppb: Coal mining, aluminum forming, photographic equipment and supplies, pharmaceutical mfg, organic chemical plastics mfg, paint and ink formulation, rubber processing, foundries, and laundries . Max concentration measured was 210,000 ppb in paint and ink industry and aluminum forming . Outfalls from 4 municipal treatment plants in southern California with primary or secondary treatment - random samples - < 10 to 400 ppb . USEPA STORET database, 1,480 data points, 38.8% pos, 10.0 ppb median . USA, 178 CERCLA hazardous waste disposal sites, 19.2% pos . Minnesota municipal solid waste landfills, leachates, 6 sites, 66.7% pos, 64-1300 ppb, contaminated groundwater (by inorganic indices), 13 sites, 53.8% pos, 1-250 ppb, other groundwater (apparently not contaminated as indicated by inorganic indices), 7 sites, 14.3% pos, 2.1-3.9 ppb(6). Water samples collected in Feb & May 1977 from Back River estuary in MD, USA, which received effluent from an urban wastewater treatment plant, contained dichloromethane. The highest levels (66 ug/l) were found in samples taken in the treatment plant just before final chlorination, suggesting that dichloromethane was derived from commercial & industrial activities in the area. Dichloromethane was detected @ levels ranging from 19-95 ug/l in 6 samples of raw sewage & effluent from Canadian sewage treatment plants. Wastewater from a USA specialty chemical plant manufacturing a broad range of chemicals container 3-8 mg/l dichloromethane. Dichloromethane was detected at concn ranging from < 0.01 to 1.0 mg/l in volatile fraction of wastewater from Oak Ridge Gaseous Plant in TN, USA. As part of the Swedish Drinking Water Project, dichloromethane was found at 640 ug/l in effluent stream from sulfate pulp mill. The amt of dichloromethane discharged was est to be 40 ton/yr. |
As part of the Drinking Water and Health pages, this fact
sheet is part of a larger publication:
National Primary Drinking Water Regulations
This is a factsheet about a chemical that may be found in some public or private drinking water supplies. It may cause health problems if found in amounts greater than the health standard set by the United States Environmental Protection Agency (EPA).
What is DCM and how is it used?
Dichloromethane (DCM) is a colorless organic liquid with a sweet, chloroform-like odor. The greatest use of DCM is as a paint remover. Other uses include: solvent and cleaning agent in a variety of industries, a fumigant for strawberries and grains; and to extract substances from foodstuffs.
The list of synonyms given below may help you find out whether you are using this chemical at home or work.
Trade Names and Synonyms:
DCM
Methylene chloride
Why is DCM being Regulated?
In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine safe levels of chemicals in drinking water which do or may cause health problems. These non-enforceable levels, based solely on possible health risks and exposure, are called Maximum Contaminant Level Goals.
The MCLG for dichloromethane has been set at zero because EPA believes this level of protection would not cause any of the potential health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a Maximum Contaminant Level (MCL). MCLs are set as close to the MCLGs as possible, considering the ability of public water systems to detect and remove contaminants using suitable treatment technologies.
The MCL has been set at 5 parts per billion (ppb) because EPA believes, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water.
These drinking water standards and the regulations for ensuring these standards are met, are called National Primary Drinking Water Regulations. All public water supplies must abide by these regulations.
What are the Health Effects?
Short-term: EPA has found dichloromethane to potentially cause the following health effects when people are exposed to it at levels above the MCL for relatively short periods of time: Damage to the nervous system and to blood.
Long-term: Dichloromethane has the potential to cause the following effects from a lifetime exposure at levels above the MCL: liver damage; cancer.
How much DCM is produced and released to the environment?
Production of DCM has been decreasing: from a high of 561 million lbs. in 1986, to roughly 410 million lbs. in 1993. It is released in wastewater primarily from the following industries: Paint and ink, aluminum forming, coal mining, photographic equipment and supplies, pharmaceutical, organic chemical/plastics, metal foundries and laundries. DCM is also formed during the chlorination of water.
From 1987 to 1993, according to EPA's Toxic Chemical Release Inventory, DCM releases to land and water totalled over 2.1 million lbs. These releases were primarily from medicinals and botanicals industries. The largest releases occurred in Connecticut and New York.
What happens to DCM when it is released to the environment?
Most DCM is released to air where it is degraded by sunlight within a few months. Releases to water evaporate very quickly. It will evaporate from soil but can also leach through soil to ground water. DCM is not likely to accumulate in aquatic life.
How will DCM be Detected in and Removed from My Drinking Water?
The regulation for dichloromethane became effective in 1994. Between 1993 and 1995, EPA required your water supplier to collect water samples every 3 months for one year and analyze them to find out if dichloromethane is present above 0.5 ppb. If it is present above this level, the system must continue to monitor this contaminant.
If contaminant levels are found to be consistently above the MCL, your water supplier must take steps to reduce the amount of dichloromethane so that it is consistently below that level. The following treatment methods have been approved by EPA for removing dichloromethane: Granular activated charcoal in combination with Packed Tower Aeration.
How will I know if DCM is in my drinking water?
If the levels of dichloromethane exceed the MCL, 5 ppb, the system must notify the public via newspapers, radio, TV and other means. Additional actions, such as providing alternative drinking water supplies, may be required to prevent serious risks to public health.
Drinking Water Standards:
Mclg: zero
Mcl: 5 ppb
DCM Releases to Water and Land, 1987 to 1993 (in pounds):
| Water | Land | |
|---|---|---|
| TOTALS (in pounds) | 1,544,694 | 556,830 |
| Top Ten States* | ||
|---|---|---|
| CT | 940,158 | 0
|
| NY | 58,400 | 155,755
|
| GA | 166,700 | 0
|
| NJ | 138,302 | 2,721
|
| WI | 0 | 139,920
|
| SC | 20,860 | 52,810
|
| MI | 39,575 | 32,900
|
| KS | 0 | 33,489
|
| MO | 0 | 27,295
|
| TX | 15,910 | 823
|
| Major Industries* | ||
|---|---|---|
| Medicinals, botanicals | 1,106,858 | 0
|
| Photographic supplies | 58,400 | 155,755
|
| Misc Indust. organics | 141,942 | 53,741
|
| Custom plastics, resins | 0 | 139,920
|
| Pharmaceuticals | 37,575 | 0
|
| Potato/corn chips&snacks | 2,000 | 32,900
|
| Air conditioning/heating | 0 | 33,489
|
| Steel pipe, tubing | 0 | 27,295
|
* Water/Land totals only include facilities with releases greater than a certain amount - usually 1000 to 10,000 lbs.