A study of more than 5,000 children in Southern California found that those kids who lived within 250 feet (76 meters) of busy roads had a 50% higher risk of having had asthma¹ symptoms in the past year. The researchers found that the asthma risk decreased to normal for children living about 600 feet or more away from a busy road. The greatest risk of asthma symptoms was found in children who had lived near busy roads since before age 2.

①Asthma is a disease of the human respiratory system in which the airways² narrow, often in response to a "trigger" such as exposure to an allergen, cold air, exercise, or emotional stress. This narrowing causes symptoms such as wheezing⁴, shortness of breath, chest tightness, and coughing, which are the hallmarks of asthma. Between episodes, most patients feel fine.

The disorder⁵ is a chronic⁶ inflammatory condition in which the airways develop increased responsiveness to various stimuli⁷, characterized by bronchial hyper-responsiveness, inflammation, increased mucus production, and intermittent⁸ airway³ obstruction⁹. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and lifestyle changes.

Public attention in the developed world has recently focused on asthma because of its rapidly increasing prevalence, affecting up to one in four urban children.②Susceptibility to asthma can be explained in part by genetic¹⁰ factors, but no clear pattern of inheritance has been found. ③Asthma is a complex disease that is influenced by multiple genetic, developmental, and environmental factors, which interact to produce the overall condition.

④During an asthma episode, inflamed¹² airways react to environmental triggers such as smoke, dust, or pollen¹³. The airways narrow and produce excess mucus, making it difficult to breathe.

 A typical inhaler, of Serevent (salmeterol)Symptomatic control of episodes of wheezing and shortness of breath is generally achieved with fast-acting bronchodilators. These are typically provided in pocket-sized, metered-dose inhalers (MDIs—see the image to the right). In young sufferers, who may have difficulty with the coordination¹⁵ necessary to use inhalers, or those with a poor ability to hold their breath for 10 seconds after inhaler use (generally the elderly), an asthma spacer is used. The spacer is a plastic cylinder¹⁶ that mixes the medication with air in a simple tube, making it easier for patients to receive a full dose of the drug (see top image) and allows for the active agent to be dispersed¹⁷ into smaller, more fully¹⁸ inhaled¹⁹ bits. A nebulizer—which provides a larger, continuous dose—can also be used. Nebulizers work by vapourizing a dose of medication in a saline solution into a steady stream of foggy vapor²⁰, which the patient inhales²¹ continuously until the full dosage is administered. There is no clear evidence, however, that they are more effective than inhalers used with a spacer. Nebulizers may be helpful to some patients experiencing a severe attack. ⑤Such patients may not be able to inhale¹⁴ deeply, so regular inhalers may not deliver medication deeply into the lungs, even on repeated attempts. Since a nebulizer delivers the medication continuously, it is thought that the first few inhalations may relax the airways enough to allow the following inhalations to draw in more medication.Since a nebulizer delivers the medication continuously, it is thought that the first few inhalations may relax the airways enough to allow the following inhalations to draw in more medication.

new words

respiratory system    呼吸系统
The respiratory system is the biological system of any organism that engages in gas exchange. Even trees have respiratory systems, taking in carbon dioxide and emitting oxygen during the day, consuming carbon dioxide and producing oxygen constantly.

hallmarks    外表
A mark indicating quality or excellence²².

symptom    症状
A symptom may loosely be said to be a physical condition which shows that one has a particular illness or disorder (see e.g. Longman, 1995). An example of a symptom in this sense of the word would be a rash. However, correctly speaking, this is known as a sign, as would any indication detectable²³ by a person other than the sufferer in the absence of verbal information from the patient.

dyspnea    呼吸困难
Dyspnea (Latin dyspnoea, Greek dyspnoia from dyspnoos - short of breath) or shortness of breath (SOB) is perceived difficulty breathing or pain on breathing. It is a common symptom of a great many disorders²⁴.

epidemiology    流行病学
In epidemiology, the prevalence of a disease in a statistical²⁵ population is defined as the ratio of the number of cases of a disease present in a statistical population at a specified²⁶ time and the number of individuals in the population at that specified time.

Genetics    遗传学
Humans began applying knowledge of genetics in prehistory with the domestication²⁷ and breeding of plants and animals. In modern research, genetics provides important tools for the investigation²⁸ of the function of a particular gene¹¹, e.g., analysis of genetic interactions. Within organisms, genetic information generally is carried in chromosomes²⁹, where it is represented in the chemical structure of particular DNA³⁰ molecules³¹.

Inheritance    遗传
Inheritance is the practice of passing on property, titles, debts, and obligations upon the death of an individual. It has long played an extremely important role in human societies.

hypersensitivity    过敏性
Hypersensitivity is an immune response that damages the body's own tissues.

spasm³²    抽搐, 痉挛
A spasm is a sudden, involuntary contraction³³ of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. A spasm is usually accompanied by a sudden burst of pain.

Inflammation    炎症
Inflammation is the first response of the immune system to infection or irritation³⁴ and may be referred to as the innate³⁵ cascade³⁶. Inflammation is characterized by the following quintet: redness (rubor), heat (calor), swelling³⁷ (tumor), pain (dolor) and dysfunction of the organs involved (functio laesa).

mucus    黏液
Mucus is a slippery secretion³⁸ of the lining³⁹ of various membranes⁴⁰ in the body (mucous membranes). Mucus aids in the protection of the lungs by trapping foreign particles that enter the nose during normal breathing. Additionally, it prevents tissues from drying out.

bronchodilator    支气管扩张
A bronchodilator is a medication intended to improve bronchial airflow. Treatment of bronchial asthma is the most common application of these drugs. They are also intended to help expand the airways and improve the breathing capacity of patients with emphysema, pneumonia⁴¹ and bronchitis.

inhaler    吸入器
An inhaler is a medical device used for delivering medication into the body via the lungs. It is often used in the treatment of asthma

nebulizer    喷雾器
In medicine, a nebulizer is a device used to administer medication to people in forms of a liquid mist to the airways. It is thus used in treating respiratory diseases. Also called "atomizers", they pump air or oxygen through a liquid medicine to turn it into a vapor, which is then inhaled by the patient.

BACKGROUND:

哮喘是一种气道的慢性炎症性疾病，可引起反复发作的喘息，气促，胸闷和咳嗽等症状，多在夜间和清晨发作。症状时隐时现，可以持续几分钟或者几天，症状可轻可重，严重时可危及生命。 哮喘的病因是多方面的，归纳之有两方面，即过敏性和非过敏性因素。过敏性因素包括花粉、灰尘、螨虫、动物毛发、食物（尤其是鱼虾类）、油漆、烟雾等；非过敏因素包括遗传、呼吸道感染、药物（如阿司匹林等）、定型发胶、精神紧张、情绪激动、剧烈运动等。 有过敏体质的人接触抗原后，使平滑肌立即发生痉挛，此为速发性哮喘反应。更常见的是不少患者在接触抗原数小时乃至数10小时后方始发作哮喘，称为迟发性哮喘反应，这是气道变应性炎症的结果。气道粘膜水肿、炎性细胞浸润、腺体分泌增中、粘液纤毛清除功能障碍，加上管腔内粘液栓阻塞也是哮喘发作的重要机制。 内源性哮喘的成因至今还未清楚，而外源性哮喘则主要由致敏原所引发。此外，这两种哮喘的成因与遗传和环境因素都有关系。哮喘是遗传病的一种，根据一些数据显示，如果双亲中有其中一位患有哮喘，则子女会有百分之二十五的机会出现哮喘的症状，而如果双亲均为哮喘患者，则子女约有四成机会患上哮喘。而当遗传的因素结合后天环境的影响，病发率便会大为提高。 “过敏性哮喘与家族遗传有部分关系，但有些孩子的过敏体质是后天形成的。”有研究显示，如果父母双方有一人有过敏体质，则生下来的孩子50%可能患有过敏病。假如父母均有过敏病，这种机会大幅增加。 “除了城市污染，空气中尘埃物及废气过多、水体污染、病从口入等都会引起疾病。比如：海鲜一类属于异性蛋白质类食物，极有可能诱发过敏性哮喘。” “加强体格锻炼，增强体质，是长期备战过敏性哮喘发作的有力措施。” 进行秋泳，因为秋泳不仅能锻炼皮肤耐受冷的刺激，利用游泳时的呼吸方法，还可增加肺活量，改善肺功能，抵挡哮喘。更重要的是，从心理上增强抗病信心。“最好在夏季便开始游泳，坚持到现在，那样身体能有一个适应过程。如果想从现在开始秋泳，要注意水温，不要过低，慢慢适应。”