• 屠呦呦与青蒿素 Tu & Arteannuin
  • 石油化工创新简史 A Petrochemistry History
  • 芳烃-改善人们生活 Aromatics Improving the Quality of Your Life
  • 百折不饶聚氨酯 Polyurethene: the Strength of Flexibility
  • 百变百丽有机硅 Silicone: the Art of Flow
  • 氯 这玩意儿 Chlorine Things


  • 强氧化剂的危害
  • 空气的威力
  • 为什么我打不开那个阀门?
  • 氮气的危险及防范
  • 物料错误混装的危害
  • 管帽和堵头-最后的防线
  • 软管破裂泄漏
  • 蒸气云爆炸
  • 危险物料的储存与运输
  • 沸腾液体膨胀蒸气爆炸(BLEVE)
  • 化学品危害性分类与标识
  • 化学品危害性其它标识方法
  • 化学品燃爆反应危害及防范
  • 化学品失控反应危害与防范-失控聚合-苯乙烯
  • 化学品失控反应危害与防范-失控聚合-丙烯酸及酯
  • 化学品遇水反应危害与防范-硅烷
  • 化学品失控反应危害与防范-失控分解-有机过氧化物
  • 工作场所危害与防范-蒸汽
  • 工作场所危害-登高作业
清除空气毒物 Taking Toxics Out of the Air

清除空气毒物 Taking Toxics out of the Air

美国环境保护署 Environment Protection Agency (epa)

Air toxics are those air pollutants that are known or suspected to cause cancer or other serious health problems such as toxicity in mutagen, reproduction, or biologically and environmentally harmful and accumulating. Each year, millions of tons of air toxics are released into the air, mostly from manmade sources, especially invisible FUGITIVE Emissions. This document describes what air toxics are, where they come from, and how they can impact people and the environment. It also describes the steps being taken by the U.S. Environmental Protection Agency to reduce emissions of air toxics from major industrial sources such as chemical manufacturing plants, petroleum refineries, and steel manufacturing plants.



The air we breathe can be contaminated with pollutants from factories, vehicles, power plants, and many other sources. These pollutants have long been a major concern because of the harmful effects they sometimes have on people’s health and the environment. Their impact depends on many factors, including the quantity of air pollution to which people are exposed, the duration of the exposures, and the potency of the pollutants. The effects of air pollutants can be minor and reversible (such as eye irritation) or debilitating (such as aggravation of asthma) and even fatal (such as cancer).



Since 1970, the Clean Air Act has provided the primary framework for protecting people and the environment from the harmful effects of air pollution. A key component of the Clean Air Act is a requirement that the U.S. Environmental Protection Agency (EPA) significantly reduce daily, so-called “routine” emissions of the most potent air pollutants: those that are known or suspected to cause serious health problems such as cancer or birth defects. The Clean Air Act refers to these pollutants as “hazardous air pollutants,” (HAP) but they are also commonly known as toxic air pollutants or, simply, air toxics.





The 1990 Clean Air Act Amendments list 188 toxic air pollutants that EPA is required to control. Examples of toxic air pollutants include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; and methylene chloride, which is used as a solvent and paint stripper by a number of industries. Examples of other listed air toxics include dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds.






Scientists estimate that millions of tons of toxic pollutants are released into the air each year. Most air toxics originate from manmade sources, including both mobile sources (e.g., cars, buses, trucks) and stationary sources (e.g., factories, refineries, power plants). However, some are released in major amounts from natural sources such as forest fires. This document focuses on EPA’s efforts, as of August 2000, to reduce routine (as opposed to accidental) emissions of toxic air pollutants from stationary sources. Routine emissions from stationary sources constitute almost one-half of all manmade air toxics emissions.




There are two types of stationary sources that generate routine emissions of air toxics:
“Major” sources are defined as sources that emit 10 tons per year of any of the listed toxic air pollutants, or 25 tons per year of a mixture of air toxics. Examples include chemical plants, steel mills, oil refineries, and hazardous waste incinerators. These sources may release air toxics from equipment leaks, when materials are transferred from one location to another, or during discharge through emissions stacks or vents. One key public health concern regarding major sources is the health effects on populations located downwind from them.

Fugitive emissions are emissions of gases or vapors from pressurized equipment due to leaks and other unintended or irregular releases of gases, mostly from industrial activities. As well as the economic cost of lost commodities, fugitive emissions contribute to air pollution and climate change. A detailed inventory of greenhouse gas emissions from upstream oil and gas activities in Canada for the year 2000 estimated that fugitive equipment leaks had a global warming potential equivalent to the release of 17 million metric tonnes of carbon dioxide, or 12 per cent of all greenhouse gases emitted by the sector. Venting of natural gas, flaring, accidental releases and storage losses accounted for an additional 38 per cent.

Fugitive emissions present other risks and hazards. Emissions of volatile organic compounds such as benzene from oil refineries and chemical plants pose a long term health risk to workers and local communities. In situations where large amounts of flammable liquids and gases are contained under pressure, leaks also increase the risk of fire and explosion.

Leaks from pressurized process equipment generally occur through valves, pipe connections, mechanical seals, or related equipment. Fugitive emissions also occur at evaporative sources such as waste water treatment ponds and storage tanks. Because of the huge number of potential leak sources at large industrial facilities and the difficulties in detecting and repairing some leaks, fugitive emissions can be a significant proportion of total emissions. Though the quantities of leaked gases may be small, gases that have serious health or environmental impacts can cause a significant problem.






Area” sources consist of smaller sources, each releasing smaller amounts of toxic pollutants into the air. Area sources are defined as sources that emit less than 10 tons per year of a single air toxic, or less than 25 tons per year of a mixture of air toxics. Examples include neighborhood dry cleaners and gas stations. Though emissions from individual area sources are often relatively small, collectively their emissions can be of concern - particularly where large numbers of sources are located in heavily populated areas.

“区域”排放源意指较小的污染排放点,每个只排放较少数量的有毒污染物到空气中。区域排放源定义为年排放量单一空气毒物少于10吨、或混合空气毒物少于25吨的排放点。比如社区中的干洗店、加油站等。尽管单个区域排放源的排放量通常比较小,但其汇集的总量令人担忧 尤其是大量此类排放源分布在人口重度密集区的时候。

EPA’s published list of “source categories” now contains 175 categories of industrial and commercial sources that emit one or more toxic air pollutants. For each of these source categories, EPA indicated whether the sources are considered to be “major” sources or “area” sources. The 1990 Clean Air Act Amendments direct EPA to set standards requiring all major sources of air toxics (and some area sources that are of particular concern) to significantly reduce their air toxics emissions.



Once released, toxic pollutants can be carried by the wind, away from their sources, to other locations. Factors such as weather, the terrain (i.e., mountains, plains, valleys), and the chemical and physical properties of a pollutant determine how far it is transported, its concentration at various distances from the source, what kind of physical and chemical changes it undergoes, and whether it will degrade, remain airborne, or deposit to land or water.




Some pollutants remain airborne and contribute to air pollution problems far from the pollution source. Other pollutants released into the air can be deposited to land and water bodies through precipitation, or by settling directly out of the air onto land or water. Eventually, a large portion of those pollutants deposited near water bodies or small tributaries will reach the water bodies via stormwater runoff or inflow from the tributary streams.



Some toxic air pollutants are of particular concern because they degrade very slowly or not at all, as in the case of metals such as mercury or lead. These persistent air toxics (as they are called) can remain in the environment for a long time (or forever, in the case of metals) and can be transported great distances.

有些有毒空气污染物尤其令人担忧,因为它们降解很慢,或干脆不会降解,比如金属中的汞和铅。这类顽固空气毒物(正如其名)可在环境中存在超长时间 (抑或永久,比如金属物),并能传播超长距离。


Often, persistent air toxics reach the ground, evaporate back into the atmosphere, and are then transported further until they are deposited on the ground again. Repeated cycles of transport, deposition, and evaporation can move toxic air pollutants very long distances. For example, toxic pollutants such as toxaphene, a pesticide used primarily in the cotton belt, have been found in the Antarctic, thousands of miles from their likely emissions sources.

经常性地,顽固空气毒物到达地面,再次蒸发进入大气,然后经传播至更远,直至再次沉积地面。反复循环的输运、沉积、蒸发可以使有毒空气污染物传输超长距离。例如,有毒污染物毒杀芬 toxaphene,一种基本用于产棉各州的杀虫剂,在南极也被测到,距离其可能的散发源已有数千英哩之遥。




People are exposed to toxic air pollutants in many ways that can pose health risks, such as by:

• Breathing contaminated air.

• Eating contaminated food products, such as fish from contaminated waters; meat, milk, or eggs from animals that fed on contaminated plants; and fruits and vegetables grown in contaminated soil on which air toxics have been deposited. 

• Drinking water contaminated by toxic air pollutants. 

• Eating contaminated soil. Young children are especially vulnerable because they may ingest contaminated soil from their hands or from objects they place in their mouths. 

• Touching (skin contact) contaminated soil, dust, or water (for example, during recreational use of contaminated water bodies).







Once toxic air pollutants enter the body, some persistent toxic air pollutants accumulate in body tissues. Also, through a phenomenon called biomagnification, predators typically accumulate even greater pollutant concentrations than their contaminated prey. As a result, people and other animals at the “top” of the food chain who eat contaminated fish or meat are exposed to concentrations that are much higher than the concentrations in the water, air, or soil.


Fish consumption advisories have been issued for thousands of water bodies nationwide, including over 52,000 lakes and over 238,000 miles of rivers. As of December 1999, 40 states have consumption advisories about mercury-contaminated fish for specific water bodies. Eleven of those states have issued state-wide advisories for freshwater lakes and rivers. Many of these water bodies were once thought to be relatively pristine. However, EPA is now finding that deposition from the air may be a major source of the pollution in these water bodies.





People who are exposed to toxic air pollutants at sufficient concentrations and for sufficient durations may increase their chances of getting cancer or experiencing other serious health effects. Depending on which air toxics an individual is exposed to, these health effects can include damage to the immune system, as well as neurological, reproductive (e.g., reduced fertility), developmental, and respiratory problems. A growing body of evidence indicates that some air toxics (e.g., DDT, dioxins, and mercury) may disturb hormonal (or endocrine) systems. In some cases this happens by pollutants either mimicking or blocking the action of natural hormones. Health effects associated with endocrine disruption include reduced male fertility, birth defects, and breast cancer.





Toxic pollutants in the air, or deposited on soils or surface waters, can have a number of environmental impacts. Like humans, animals can experience health problems if they are exposed to sufficient concentrations of air toxics over time. Numerous studies conclude that deposited air toxics are contributing to birth defects, reproductive failure, and disease in animals. Persistent toxic air pollutants are of particular concern in aquatic ecosystems because the pollutants accumulate in sediments and may biomagnify in tissues of animals at the top of the food chain to concentrations many times higher than in the water or air. Toxic pollutants that mimic hormones also pose a threat to the environment. In some wildlife (e.g., birds, shellfish, fish, and mammals), exposures to pollutants such as DDT, dioxins, and mercury have been associated with decreased fertility, decreased hatching success, damaged reproductive organs, and altered immune systems.




The Pre-1990 “Risk-Only” Approach

Prior to 1990, the Clean Air Act directed EPA to regulate toxic air pollutants based on the risks each pollutant posed to human health. Specifically, the Act directed EPA to: 

•      Identify all pollutants that caused “serious and irreversible illness or death.”

•      Develop standards to reduce emissions of these pollutants to levels that provided an “ample margin of safety” for the public.






While attempting to control air toxics during the 1970s and 1980s, EPA became involved in many legal, scientific, and policy debates over which pollutants to regulate and how stringently to regulate them. Debates focused on risk assessment methods and assumptions, the amount of health risk data needed to justify regulation, analyses of the costs to industry and benefits to human health and the environment, and decisions about “how safe is safe.”



During this time, EPA was still developing methods to assess risk. These methods were essential tools that would be needed to establish the scientific basis for making risk-based decisions about air toxics. While EPA and the scientific community gained valuable knowledge about risk assessment methods through this work, the chemical-by-chemical regulatory approach—an approach based solely on risk—proved difficult. In fact, in 20 years, EPA regulated only seven pollutants (asbestos, benzene, beryllium, inorganic arsenic, mercury, radionuclides, and vinyl chloride). Collectively, these standards cut annual air toxics emissions by an estimated 125,000 tons.

这一时期,EPA还是不断制定了各种方法以评估风险。这些方法当时作为基础工具用以建立科学基准来对空气毒物进行“风险为准”的判定。尽管EPA和科学界通过这一工作对风险评估方法获得了宝贵的知识,但针对逐个化学品立法的方法 即只查风险方法 证明是行不通的。事实上,EPA在二十年里只规范了七种污染物 (石棉、苯、铍、无机砷、汞、放射性同位素、以及氯乙烯)。总体来说,这些标准还是削减了年空气毒物排放约125,000吨。

The 1990 Clean Air Act Amendments:

A “Technology First, Then Risk” Approach

Realizing the limitations of a chemical-by-chemical decision framework based solely on risk, and acknowledging the gaps in scientific and analytical information, Congress adopted a new strategy in 1990, when the Clean Air Act was amended. Specifically, Congress revised Section 112 of the Clean Air Act to mandate a more practical approach to reducing emissions of toxic air pollutants.





This approach has two components. In the first phase, EPA develops regulations - MACT (Maximum Achievable Control Technology) standards - requiring sources to meet specific emissions limits that are based on emissions levels already being achieved by many similar sources in the country. Even in its earliest stages, this new “technology-based” approach clearly produced real, measurable reductions. In the second phase, EPA applies a risk-based approach to assess how these technology-based emissions limits are reducing health and environmental risks. Based on this assessment, EPA may implement additional standards to address any significant remaining, or residual, health or environmental risks. EPA completed development of its strategy for addressing residual risks from air toxics in March of 1999.

这一方法包含两个部分。第一阶段,EPA制定规则 – MACT(最大可及控制技术)标准 要求排放源达到特定的排放限值,即国内其它类似排放源已达到的排放水平。这种新的“技术为本”的方法即使在其最初阶段就取得了实在的、可量化的减排效果。第二阶段,EPA 采用“风险为准”的方法评估这些基于技术的排放限值如何降低健康与环境风险。在此评估基础上,EPA 可以实施进一步的标准以处置其它显著的剩余、残余的健康环境风险。EPA19993月完成制定了这一策略,以处置空气毒物剩余的风险。




As of August 2000, EPA has issued 45 air toxics MACT standards under Section 112 of the Clean Air Act Amendments. These standards affect 82 categories of major industrial sources, such as chemical plants, oil refineries, aerospace manufacturers, and steel mills, as well as eight categories of smaller sources, such as dry cleaners, commercial sterilizers, secondary lead smelters, and chromium electroplating facilities. EPA has also issued two standards under Section 129 of the Clean Air Act to control emissions, including certain toxic pollutants, from solid waste combustion facilities (one standard for municipal waste combustors and the other for medical waste incinerators). Together, these standards reduce emissions of over 100 different air toxics. When fully implemented, all of these standards will reduce air toxics emissions by about 1.5 million tons per year - almost 15 times the reductions achieved prior to 1990. Each of the final rules developed since 1990 is summarized in an appendix to this document (pages 9 to 31). These summaries describe the sources for which final rules have been issued as of August 2000, the types of pollutants the sources emit, and how EPA’s rules are reducing their emissions.


20008月,EPA根据清洁空气法修正案112节要求发布了45项空气毒物MACT标准。这些标准涉及主要工业排放源中的82个类别,比如化工厂、炼油厂、航空制造、钢铁厂、以及8个次要排放源类别,比如干洗业、商用消毒业、二级熔铅行业、镀铬业等。EPA还根据清洁空气法129节要求颁布了两项标准用以控制排放,包括某些固废焚烧厂的有毒空气污染物(一项针对城市废物焚烧装置,另一项针对医用废弃物焚烧炉)。汇总起来,这些标准涉及过百种空气毒物的减排。如能完全实施,所有这些标准可以每年减少约150万吨空气毒物的排放 几乎是1990年以前减排量的15


Some of these air toxics rules have the added benefit of reducing ground-level ozone (urban smog) and particulate matter. This occurs because some air toxics are also smog-causing volatile organic compounds (VOCs) (e.g., toluene) or particulate matter (e.g., chromium). In addition, some of the technologies and practices designed to control air toxics also reduce VOCs or types of particulate matter that are not currently among the 188 listed air toxics. Reductions of smog-causing pollutants and particulate matter are important because of the health and environmental problems they can cause. Most notably, urban smog can cause respiratory problems and can damage vegetation, and particulate matter can cause many detrimental impacts on human health, such as bronchitis, lung damage, increased infection, aggravation of asthma, and premature death. In addition many of these pollutants can contribute significantly to impaired visibility in places, such as national parks, that are valued for their scenic views and recreational opportunities.

部分空气毒物规定有助于减少地面臭氧(城市污霾)和颗粒物。主要因为有些空气毒物也属于引发污霾的挥发性有机物(VOC) (比如甲苯)或颗粒物(比如铬)。此外,有些用于控制空气毒物的技术和做法也有助于减少目前尚未计入188种空气毒物的挥发性有机物(VOC)或颗粒物。减少引发污霾的污染物和颗粒物确属必要,主要因为其造成的健康和环境问题。尤其值得注意,城市污霾也能引发呼吸问题、破坏植被、对人类健康造成不利影响,比如支气管炎、肺部损害、增加感染、加重哮喘、以及早逝等。此外,此类污染物还显著降低各地的能见度,比如国家公园,而这些地方的价值正在于其景观和休闲活动。


EPA has consistently worked to develop air toxics standards that achieve the required reductions in air pollution while providing regulated communities with as much flexibility as possible in deciding how to comply with the standards. For example, under a flexible regulation, industries may reduce their emissions by redesigning their processes, capturing and recycling emissions, changing work practices, or installing any of a variety of control technologies. Flexibility helps industries minimize the cost of compliance and encourages pollution prevention. To provide flexibility, EPA makes every effort to develop standards that are based on performance measures rather than specific control devices, and that allow for equivalent alternative control measures.



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