38 · 水和旅行者
Water and the Traveller
区分观点、依据、例子与限制，用自己的话准确重建论述。
饮水提示：末段保留作者原意，但不能据触感或放凉就判断饮水安全。现实中应遵循当地饮水公告及可靠的净水指引；依据见本册导论中的CDC引用。
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Contamination of water supplies is usually due to poor sanitation close to water sources, sewage disposal into the sources themselves, leakage of sewage into distribution systems, or contamination with industrial or farm waste. Even if a piped water supply is safe at its source, it is not always safe by the time it reaches the tap. Intermittent tap water supplies should be regarded as particularly suspect.
Travellers on short trips to areas with water supplies of uncertain quality should avoid drinking tap water, or untreated water from any other source. It is best to keep to hot drinks, bottled or canned drinks of well-known brand names—international standards of water treatment are usually followed at bottling plants. Carbonated drinks are acidic, and slightly safer. Make sure that all bottles are opened in your presence, and that their rims are clean and dry.
Boiling is always a good way of treating water. Some hotels supply boiled water on request and this can be used for drinking, or for brushing teeth. Portable boiling elements that can boil small quantities of water are useful when the right voltage of electricity is available. Refuse politely any cold drink from an unknown source.
Ice is only as safe as the water from which it is made, and should not be put in drinks unless it is known to be safe. Drinks can be cooled by placing them on ice, rather than by adding ice to them.
Alcohol may be a medical disinfectant, but should not be relied upon to sterilize water. Ethanol is more effective at a concentration of 50-70%; below 20%, its bactericidal action is negligible. Spirits labelled 95 proof contain only about 47% alcohol. Beware of methyl alcohol, which is very poisonous and should never be added to drinking water.
If no other safe water supply can be obtained, tap water that is too hot to touch can be left to cool and is generally safe to drink. Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, should know about the various possible methods for making water safe.
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整篇课文
Contamination of water supplies is usually due to poor sanitation close to water sources, sewage disposal into the sources themselves, leakage of sewage into distribution systems, or contamination with industrial or farm waste. Even if a piped water supply is safe at its source, it is not always safe by the time it reaches the tap. Intermittent tap water supplies should be regarded as particularly suspect.
Travellers on short trips to areas with water supplies of uncertain quality should avoid drinking tap water, or untreated water from any other source. It is best to keep to hot drinks, bottled or canned drinks of well-known brand names—international standards of water treatment are usually followed at bottling plants. Carbonated drinks are acidic, and slightly safer. Make sure that all bottles are opened in your presence, and that their rims are clean and dry.
Boiling is always a good way of treating water. Some hotels supply boiled water on request and this can be used for drinking, or for brushing teeth. Portable boiling elements that can boil small quantities of water are useful when the right voltage of electricity is available. Refuse politely any cold drink from an unknown source.
Ice is only as safe as the water from which it is made, and should not be put in drinks unless it is known to be safe. Drinks can be cooled by placing them on ice, rather than by adding ice to them.
Alcohol may be a medical disinfectant, but should not be relied upon to sterilize water. Ethanol is more effective at a concentration of 50-70%; below 20%, its bactericidal action is negligible. Spirits labelled 95 proof contain only about 47% alcohol. Beware of methyl alcohol, which is very poisonous and should never be added to drinking water.
If no other safe water supply can be obtained, tap water that is too hot to touch can be left to cool and is generally safe to drink. Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, should know about the various possible methods for making water safe.
供水受到污染，通常是因为水源附近卫生条件差、污水直接排入水源、污水渗进输水系统，或者水受到工业和农业废物污染。即使自来水在水源处是安全的，到达水龙头时也未必仍然安全。尤其需要警惕的是时断时续的自来水供应。
短期前往供水质量不明的地区旅行，应避免喝自来水，也不要喝任何其他来源的未经处理的水。最好选择热饮，以及知名品牌的瓶装或罐装饮料，因为灌装厂通常遵循国际水处理标准。碳酸饮料呈酸性，相对稍安全一些。要确保所有瓶子都当着你的面开启，瓶口边缘也保持清洁、干燥。
把水烧开，一向是处理水的好办法。有些酒店可以应要求提供开水，用来饮用或刷牙。只要当地电源电压合适，能烧开少量水的便携式电热器就很实用。对于来源不明的冷饮，应当礼貌地谢绝。
冰块是否安全，取决于制冰的水是否安全；除非确认安全，否则不要把它加进饮料。可以把饮料容器放在冰上降温，而不是直接往饮料里加冰。
酒精虽然可以作医用消毒剂，却不能依赖它给饮用水消毒。乙醇在百分之五十到百分之七十的浓度下较有效；低于百分之二十，杀菌作用便微乎其微。标着“95 proof”的烈酒，酒精含量其实只有约百分之四十七。尤其要警惕甲醇，它有剧毒，绝不能加入饮用水。
如果找不到其他安全水源，烫得不能碰的自来水可以放凉，通常可以安全饮用。打算前往偏远地区，或者到不容易获得安全饮用水的国家居住的人，应当了解各种可能的水处理方法。
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