首页
登录
职称英语
About two-thirds of the world’s population is expected to live in cities by the
About two-thirds of the world’s population is expected to live in cities by the
游客
2023-12-30
8
管理
问题
About two-thirds of the world’s population is expected to live in cities by the year 2020 and, according to the United Nations, approximately 3.7 billion people will inhabit urban areas some 10 years later. As cities grow, so do the number of buildings that characterize them: office towers, factories, shopping malls and high-rise apartment buildings. These structures depend on artificial ventilation systems to keep clean and cool air flowing to the people inside. We know these systems by the term "air-conditioning"
Although many of us may feel air-conditioners bring relief from hot, humid or polluted outside air, they pose many potential health hazards. Much research has looked at how the circulation of air inside a closed environment—such as an office building—can spread disease or expose occupants to harmful chemicals.
One of the more widely publicized dangers is that of Legionnaire’s disease, which first recognized in the 1970s. This was found to have affected people in buildings with air-conditioning systems in which warm air pumped out of the system’s cooling towers was somehow sucked back into the air intake, in most cases due to poor design. This warm air was, needless to say, the perfect environment for the rapid growth of disease carrying bacteria originating from outside the building, where it existed in harmless quantities. The warm, bacteria-laden air was combined with cooled conditioned air and was then circulated around various parts of the building. Studies showed that even people outside such buildings were at risk if they walked past air exhaust ducts. Cases of Legionnaire’s disease are becoming fewer with newer system designs and modifications to older systems, but many older buildings, particularly in developing countries, require constant monitoring.
The ways in which air-conditioners work to "clean" the air can
inadvertently
cause health problems, too. One such way is with the use of an electrostatic precipitator, which removes dust and smoke particles from the air. What precipitators also do, however, is to emit large quantities of positive air ions into the ventilation system. A growing number of studies show that overexposure to positive air ions can result in headaches, fatigue and feelings of irritation.
Large air-conditioning systems add water to the air they circulate by means of humidifiers. In older systems, the water used for this process is kept in special reservoirs, the bottoms of which provide breeding grounds for bacteria and fungi which can find their way into the ventilation system. The risk to human health from this situation has been highlighted by the fact that the immune systems of approximately half of workers in air-conditioned office buildings have developed antibodies to fight off the organisms found at the bottom of system reservoirs. Chemical disinfectants, called "biocides", that are added to reservoirs to make them germ-free are dangerous in their own right in sufficient quantities, as they often contain compounds such as pentachlorophenol, which is strongly linked to abdominal cancers.
Finally, it should be pointed out that the artificial climatic environment created by air-conditioners can also adversely affect us. In a natural environment, whether indoor or outdoor, there are small variations in temperature and humidity. Indeed, the human body has long been accustomed to these normal changes. In an air-conditioned living or work environment, however, body temperatures remain well under 37° C, our normal temperature. This leads to a weakened immune system and thus greater susceptibility to diseases such as colds and flu. [br] Flu and colds are caused mainly due to ______.
选项
A、bacteria
B、temperatures
C、chemicals
D、biocides
答案
B
解析
由末段最后二句可知,流感和感冒主要是人的体温低于正常体温,导致免疫力降低引起的,故选B“温度”。同时排除A“细菌”、C“化学物质”和D“杀菌剂”。
转载请注明原文地址:https://tihaiku.com/zcyy/3318516.html
相关试题推荐
AAlikemostotherendangeredanimals,theworld’sBremainingcariboupopulations
CaliforniaAhasnotonlythelargestBpopulationbutalsotheCmoreproductivee
AmongcentralAsia’soldestcitiesATashkentis,theBculturalcapitalandCecon
Apartmentsare______tobebuiltincitiesthaninsuburbanorruralareas.A、more
BecauseofCanada’sabundantproductionandrelativelysmallpopulation,itisa
Consistentlyrankingamongthecleanest,mostlivablecitiesintheworld,Vanco
TheUnitedStatescountsitspopulationeverytenyears,andeachcensusrev
TheUnitedStatescountsitspopulationeverytenyears,andeachcensusrev
TheUnitedStatescountsitspopulationeverytenyears,andeachcensusrev
TheUnitedStatescountsitspopulationeverytenyears,andeachcensusrev
随机试题
Itisadvisedthat______(工程不动工)untilweaccepttheorderfromthemanager.thep
Somepeoplesaythetraditionalcalendarof180daysnolongermeetsthenee
Fromthepassagewecaninfertaboois______.[br]Apartfromthisnewundersta
[originaltext]W:MayIcomein?M:Comein,please.Doyouknowwhattimeitis
老子云:“介抱之木,生于毫末。千层之台,起于土。千里之行,始于足下。”能够说的是
用承载板法测定土基回弹模量,当回弹变形值超过()时即可停止加载。A.0.5mm
不属于数据库基本结构的是( )。A.原始数据 B.概念数据层 C.数据共享
嗜铬细胞瘤术前准备的药物为A.酚妥拉明 B.酚苄明 C.手术切除 D.显像
当经济发展到一定阶段以后,产业布局政策的侧重点就会转变为强调地区经济发展的( )
某新建排涝泵站,共安装4台机组,单机配套功率400KW。泵站采用正向进水方式布
最新回复
(
0
)