Effects of air pollution 空气污染的影响
Only a few examples of pollution effects can be considered in the sections to follow.关于污染影响的例子只有少部份能够被研究分析。
All of the examples identify local, observable, or measurable impacts, because it is very difficult to develop direct relationships between specific pollutants and effects for exposures over the longer term or at great distances.这部分例子是局部的，可见的或可测量的。因为去研究分析那些被长期地、大面积地暴露的特殊污染物之间的关系是很困难的。
A more complete decription could fill several books.如果要完整地描述这些特殊污染物的话几乎可以写满几本书。
One of the most obvious local effects of particles in the atmosphere is a reduction in visibility.存在于空气中的颗粒所产生的影响是降低了能见度。
Only a few decades ago, soiling by soot and smoke was clearly apparent in almost every urban center.仅在几十年前，几乎每个市中心都明显地出现了煤烟和烟雾的污染。
Reduction in visibility results in a social cost due to slowdown of air traffic and the need for instrument-guided landing systems. 能见度降低导致的社会资源浪费，因为放缓的空中交通需要必要手段引导着陆系统。
In the air pollution episodes cited, the local presence of gases was objectionable because of odor, taste, or obvious corrosive or chemical effects. 由空气污染事件引起，使当地的气体是令人讨厌，因为受到气味，口味，或明显的腐蚀或化学的影响。
Today these gross sensory insults are rarely encountered.现在，这些恶心难受的感觉很少遇到了。
However, subtle health effects persist, such as eye or nose irritation or difficult breathing.不过，不易察觉的健康影响仍然存在，如眼睛或鼻子的不适，或呼吸困难。
In the extreme, health effects extend to the brain (CO) and stomach (several pollutants alone or in combination) .更严重的话，这些影响会伤害大脑（CO）和胃（若干污染物单独或联合在一起）。
Damage to vegetation due to chronic exposure to atmospheric pollutants may be one of the more apparent precursor symptoms leading to identification of chronic air pollution.长期暴露于大气污染物中的植被所遭受的破坏也许是空气长期污染症状的一种较明显的前兆。
Health effects Health effects were the dominant considerations in early air pollution episodes for obvious reasons.显然地，在早期的空气污染过程中，对健康的影响是应该优先考虑的事项。
While the specific pollutant or groups of pollutants generating the observed effects frequently could not be identified, there was sufficient information to implicate certain pollutants as significant contributors.当这种特殊的污染或多种污染物产生的被频繁观测到的影响不能被识别出来时，就有足够的证据暗示某些污染物充当重要的源头。
Early research to relate pollutant concentrations and effects was concentrated on these clearly identifiable pollutants.早期将污染物浓度和影响相联系的研究是专注于这些能清楚辨认的污染物上。
The human respiratory system is quite efficient in filtering the larger particles out of the air we breathe.人类的呼吸系统善于将我们吸入空气中的颗粒物过滤出来。
Particles smaller than about 5μμμμm, however, can penetrate to the lungs and be deposited in the alveoli.但是，粒径小于5μm的颗粒能通过的（过滤）到达肺部并沉积在肺泡中。
For example, cigarette smoke particles are smaller than 1μμμμm, and they enter and are deposited in the alveoli.例如，香烟烟雾的粒径小于1μm，它们进入肺部并沉积在肺泡里。
Some particles are particularly damaging because they adsorb gases which cause more intense irritation locally.某些颗粒的损坏尤其严重，因为它们可以吸附一些对局部开成更强烈刺激的气体。
Gases also penetrate into the deepest lung pockets. 气体也会透入到最深层的肺部。
Both particles and gases entering the body through the respiratory system can affect the gastrointestinal system, as was reported in the Donora incident.通过呼吸系统进入人体的颗粒物和气体都能影响肠胃系统，正像多诺拉事件中报道的一样。
Some chemical, such as lead, can enter the human bloodstream either from the digestive system (ingestion) or by passing through the lung membranes (the respiratory system), and airborne tritium and a few other chemical can enter the bloodstream through the skin.一些化学物质，例如铅， 可以通过消化系统（吸收）或者穿透肺膜（呼吸系统）进入人体的血液循环系统，空气中的氚（三重氢）和其它一些化学物质可以通过皮肤进入血液循环系统。
Each pollutant affects the human body differently, and records of effects have been assembled relating the intensity to the period of exposure for various pollutants.每一种污染物对人体的影响不同，影响效果的记录已经被编排起来，这种编排是与各种污染物的曝光周期相关联的。
Health effects of carbon monoxide are clearly detectable at 4 percent carboxyhemoglobin (COHb) in the blood, and possibly as low as low as 2.5 percent COHb. 在4%的羧络[碳氧]血红蛋白这一测限上，一氧化碳对健康的影响可以被明显地发现出来，这一测限可以低至以2.5%羧络[碳氧]血红蛋白。
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