[al:新概念英语（四）] [ar:MP3 同步字幕版（美音）] [ti:Water and the Traveller] [by:更多学习内容，请到yingyu.chazidian.com搜索“新概念”] [00:00.54]Lesson 38 [00:02.41]Water and the traveller [00:09.59]What does this text describe? [00:13.50]Contamination of water supplies is usually due to poor sanitation close to water sources, [00:21.30]sewage disposal into the sources themselves, leakage of sewage into distribution systems or contamination with industrial or farm waste. [00:32.17]Even if a piped water supply is safe at its source, it is not always safe by the time it reaches the tap. [00:39.72]Intermittent tap-water supplies should be regarded as particularly suspect. [00:45.76]Travellers on short trips to areas with water supplies of uncertain quality [00:51.08]should avoid drinking tap-water, or untreated water from any other source. [00:56.95]It is best to keep to hot drinks, bottled or canned drinks of well-known brand names-international standard of water treatment are usually followed at bottling plants. [01:08.27]Carbonated drinks are acidic, and slightly safer. [01:12.24]Make sure that all bottles are opened in your presence, and that their rims are clean and dry. [01:19.14]Boiling is always a good way of treating water. [01:22.36]Some hotels supply boiled water on request and this can be used for drinking, or for brushing teeth. [01:29.49]Portable boiling elements that can boil small quantities of water are useful when the right voltage of electricity is available. [01:37.86]Refuse politely any cold drink from an unknown source. [01:43.22]Ice is only as safe as the water from which it is made, [01:46.79]and should not be put in drinks unless it is known to be safe. [01:51.80]Drinks can be cooled by placing them on ice rather than adding ice to them. [01:58.17]Alcohol may be a medical disinfectant, but should not be relied upon to sterilize water. [02:05.57]Ethanol is more effective at a concentration of 50-70 percent; [02:10.72]below 20 per cent, its bactericidal action is negligible. [02:15.91]Spirits labelled 95 proof contain only about 47 per cent alcohol. [02:22.63]Beware of methylated alcohol, [02:24.89]which is very poisonous and should never be added to drinking water. [02:30.71]If no other safe water supply can be obtained, [02:34.45]tap water that is too hot to touch can be left to cool and is generally safe to drink. [02:41.50]Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, [02:49.29]should know about the various possible methods for making water safe.